my .02 on cams for boosted motors [Archive] - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Z U L8R

03-02-2010, 09:19 AM

all they do on boosted motors is make a little more power up top to lose spool down low.

will you ever hear anyone say, bigger cams made my turbo kick in sooner than stock cams did? no

i'm talking boosted motors. and boosted motors under 450whp

for N/A motors, cams would be the the first big thing you do. on a boosted motor, cams should be the last thing you do. bigger turbo and the appropriate supporting mods should be the first thing you do for a boosted motor.

i know everyone with mild to stock 240's runs out to buy cams thinking they're magical looking for the results that a bigger turbo or more boost would get them. it's not cam's you're wanting

if you don't have a turbo on your motor and you're looking for that big bump in power then YES, cams are what you should get.

if you want a fun responsive boost curve then you don't want aftermarket cams. all you're doing is pushing the powerband up higher.....yet you want quick response.....doesn't that seem counterproductive?

now lets say you don't give a shit about response, you're pissed you're making 390 and you're maxed out on what you can do. you're so close to making 400 but you don't wanna get another turbo or turn the boost up any more or redo all the piping and what not.....ok bro, get some cam's, then you can get your 400hp goal you fell shy of up top....but you're turbo's gonna kick in later than it does now. if that's the results you're going for then get cams.

i just think a lot of people are misinformed. they want to get good stuff for their cars, they get the money, but they don't know what to, and what not to, spend their money on. so they do what everyone else (who's not boosted) does, runs out and buys some cams cause they make more power......yes............. they will.....................eventually.

if what you want is more power NOW. then what you're wanting is more boost, not more cam.

stock cams ftmfw http://240atlanta.com/forums/images/smilies/goodjob.gif

my .02

Dave

DC29

03-02-2010, 10:02 AM

are you talkin strictly 4 cyl?

cause id take a N/A built and tuned the correct way over a boosted motor any day if im going for strictly response.

we run toyota 4cyl's in our midget sprint cars that respond faster than oprah to cake. they also make 450hp n/a.

Z U L8R

03-02-2010, 10:27 AM

lol @ oprah

yeah i'm just talking turbo motors.

i'm not arguing responsiveness of n/a vs boost or anything like that.

i'm just trying to help people with boosted motors understand why cams should be the last thing on the shopping list, not vice versa, which is what i see most often.

they wanna buy a mod for their car because they want to increase the performance....but they don't know what they're buying and how that mod will change how the car performs....which is why i made this thread.

hope it helps someone,

Dave

codyace

03-02-2010, 10:51 AM

i'm just trying to help people with boosted motors understand why cams should be the last thing on the shopping list, not vice versa, which is what i see most often.

I 100% disagree with this. Cams are an EXTREMLY important upgrade for our engines in regard to power output. You run my setup with a set of stock cams, and it would easily spool later, make a HUGE deal less power, and much less torque as well.

Heck even in stock motors, a nice mild to medium set of cams (and by mild I mean a 256-264 duration) will be the best thing you can run. It not only frees up power N/A (assuming thier was no turbo) but also frees up a ton of power when boosted. Remember, the motor is an airpump - the more efficiently you can get it in and out, the better torque/power you will make.

jspaeth

03-02-2010, 11:03 AM

I am not going to argue with you (Dave), because you know way more than I do, but I agree with Cody.

But I used to have a stock motor 2871r setup.

I added springs, retainers, HKS 264/264 cams, and a Greddy Intake manifold.

The old dyno is is solid, the new one is dashed:

http://makingapril.com/greg/justin/newdyno.jpg

My new dyno sheet shows that I have lost ~10-15 ft-lbs across the board, and that the torque comes in about 700 RPMs LATER than before.

There are 2 things to be said.

1) I don't believe the person that tuned my car did very much in the way of ignition timing with the new setup to maximize the benefits of the new cams (perhaps why tq is low across the board).

2) This person did not set up my boost controller well while the car was on the dyno.

*** Notice the drop off of power in the new setup around 6750 or so.
Driving the car on the street, the car was hitting 19 psi, but then was dropping down to only 16 psi from 6500 onward.

I tinkered with the boost controller, and now can hold 19-20 psi all the way to redline..

So that means my hp and tq curves aren't dropping off as much as you see.

*** Also, he didn't have the LOW end of the boost controller (AVC-R) set up well.

From the looks of the dyno, it looks like I am not hitting full boost until nearly 4500 RPM.

However, on the street, with my new EBC settings, I hit full boost (19-20 psi) in all gears, (starting from let's say 2500 RPM) by 3800 RPM or so.

3) My AFRs under full boost with the new setup/tune go as low as 10-11.
VERY rich.

Conclusion:

I think with some proper fuel/ignition tuning, as well as NOW having the boost controller set up the way that it should be, I believe my new setup (cams and Greddy IM) spools up NEARLY (maybe 200 RPM later) as early as the old setup, would make AS much tq, and most importantly, stretches my tq/powerband by as much as 1000-1500 RPM.

I should again stress that the dyno sheet above for the "new" setup (dashed) was under conditions where the boost controller was not setup properly (not reaching full boost until 4500, tapering off at 6500) and the tune is VERY rich and also the timing is weak.

Z U L8R

03-02-2010, 11:45 AM

mr_eh

03-02-2010, 11:51 AM

so should i just leave stock cams on my motor if i have a big turbo? :) or are you saying not to purchase cams with the assumption it adds more power?

fwiw my build consists of a 35r 1.06 exhaust housing and 264/272 hks step twos

jspaeth

03-02-2010, 11:52 AM

Honestly, I respect your opinion.

Of all the installs I've done to my car, I like the cams the most. I just REALLY enjoy being able to wind the car out (with power) all the way to like 8000 RPMs.

PLUS, they make the motor sound so much better when you are ripping through the high RPM range :naughtyd:

codyace

03-02-2010, 01:29 PM

i'm totally not saying you're dumb if you get cams on a boosted motor.

as far as your set up, you're pushing that 28/71 to what it can do, in it's happy range of ~20 psi

so if you wanted a little more power on top of what it already did, without messing with your set up, than yeah, cams are warranted.

but if you wanted to make 400 or 450hp

i'd say, put back in the stock cams, with a gt30 or another turbo that'll get you there, and crank it up, and it would do it. then if you wanted to tap that set up out, THEEEN get the cams, like you did.

Certainly not running cams will get you power that you want, but always at the expense of more boost. This IMO is not a 'condusive' setup, as now you're simply introducing an un needed amount of heat into the combustion procee, thus requiring very limited timing to be introduced, and more race gas oriented fuel to fend of detention. Is it safer to run more boost, with more fuel with less timing? Usually yes, but there is a point where it becomes to much, and hurts power. I'd rather run 15 psi with some timing, than 20 psi without any.

you also didn't go stupid crazy and get 272's which is good.

True, and I think this is where you may 'hate' on 'turbo cams'. I too hate cams that are 'marketed for for turbo'. THis applies to Honda's, LSx, Modular, everything! Turbo cams usually offer very low (close to zero) seperation between the lobnes (which is good) but often run crappy lifts with poor duration (either to little or to much)

i just want ppl just getting their sr or rb or whatever swap done, to know that the first mod they need to run out and get is a better turbo, the fuel system and tuning to manage it, and a good electronic boost controller, instead of the FIRST thing they always get, which is cams. lol

I certainly agree with this, but at the same time, if the motor is apart (assuming most people tear them down for inspection) there is no better time to put cams in, as it's easily accessible.

To me, even if it was N/A, throwing a set of persay Jim Wolf S3's or s4's in, will make better overall power and torque, and then even moreso with FI

lose spool down low to gain power up top towards the end. sometimes it has it's place, most of the time though what people are really wanting, they'd get from more boost/bigger turbo not more cam.

Very true. There is certainly somethign to be said about running a larger turbo at less boost, than a smaller one at more. BUT then there are nut jobs like me, who are content with the t2 spool time, but want a tad more power. I honestly can say, a 30r car is boring to me in street trim. Very fun for street racing, and would be awesome with a solid valvetrain that could use the RPM's, but for a car that has a 7800 rev limit, it's just not worth the 4500/5000 rpm full spool for me (and I'm a road race guy)

i hate cams....unless in a chevy LS motor with some nitrous :D....but if i were to boost the LS motor...i dunno i might do a cam just so it doesn't make 9million foot lb of torque at 3,000 rpm hahhaa. that'd be where i would WANT it to make less power so soon and more power up top lol.

One of my best friends has a WS6 with a built 6.0. 250 single stage for now, looking for a dual setup her soon. Talk about fun :D

But even here, cam selection for a 3500 lb vs 2600 lbc car are also much different. LSx in 240 can run a much more wild cam with the tiny car :D

Dave =][/QUOTE]

so should i just leave stock cams on my motor if i have a big turbo? :) or are you saying not to purchase cams with the assumption it adds more power?

fwiw my build consists of a 35r 1.06 exhaust housing and 264/272 hks step twos

You definatly should get cams for your setup, but I would not be going with that staggared setup. SR20's simply don't like staggered cams - there is obviously a reason for this that I don't know how to explain (i'm no engineer lol) but there is some physical reason why.

35r you want 264 at the minimum, 272 probably best...and a nice free flowing exhaust. No reason to sacrifice 50 hp on the big end of the power band for 20 ft lbs at the low end where your turbo isn't even making power.

Z U L8R

03-02-2010, 03:04 PM

YESSS!!!

i was hoping someone would disagree cause i wanted to see why.

Cody i totally agree with you on your first post, on YOUR set up the stock cams would be a restriction cause you're making 400+hp

but i promise you if you went back with the stock cams your boost would come on sooner.

even on my 2j , yes i'm gonna do cams....but yes i'm also shooting for 600rwhp and i'm totally gonna see what it can do with the stock usdm cams before i change em. then i'll post up before and after.

my emphasis is on lower hp cars. people have the wrong impression of what cams will do.

if they're looking for mild instant power with the best powerband getting some big ass cams is NOT a good upgrade.

that's the point i'm making.

i've wanted this discussion for a while

Dave =]

codyace

03-02-2010, 03:53 PM

Oh for sure. I guess (with anything car related really) we all fight that fine line with the cars, in regard to response v power, and realistically we all want the most of both, but naturally need to give up one for the other (with most leaning to HP).

Thnk of this for example:
A stock t25 car, lets say with the basics (370cc, walbro 255, stock ecu) at 14 psi of boost will make roughly 240 whp. This will max the injectors, ecu, and maf all at the same time.

Now take that same t25 car, but now bring the boost back down to 7-8 psi, but add a set of S3 JWT cams (260 duration, but 11.5 lift). These will work just fine without a retune, but now if you log the car, you'll notice thta your fuel cycle, and your maf are pegged, yet again you'll see that same 240-250 whp at stock boost levels.

If you overlay the two powerbands, you get an odd comparison - the t25 (lets face it) isn't known for top end...yet with the addition of some medium sized cams, you'll all of a sudden gain much more torque for a longer period of time, and more HP to redline, BUT (as you point out) at the loss of some response (at this rate we'll say 500 rpm).

But if you were to take the average power and torque figures form the stock cam vs JWT cam car, you'll see that the JWT (or even HKS 264, or Tomei 256, or similar) will have significantly more average power than the stock cams. So now, even though the powerband is obviously shifted to the top end, and even though you loose some grunt, the car will have more average power across the rev range; this all translates to a car with cams being faster, and quicker.

Now if you were to compare time slips, there is no doubt the stock cam car will probably make it to the 330' mark maybe a hair faster, and maybe even at the 1/8th, but at the end, the cammed car will be significantly ahead (and obviously with a higher trap).

So with all of this also considered, lets also factor in 'traction'. Sure it's nice to claim to have some low end, but now we also are battling traction (which is another conversation in itself haha). Is it worth having that 500 extra RPM of spool, only to blow the rear tires off? Undoubtedly the car with cams will not hit initially as hard, be a bit soft, yet through a mechanical traction control (of sorts, with the 'less torque generating) cams, the cammed car will take off and pounce ahead. THis applies to all motorsport, including (dare I say) street racing. The fastest car has the most power per traction, so even a turbo that spools off the hit, may not be the quickest.

Lastly, you also need to look at usable powerband of the car. I know on track, I don't see much, if any time below 3500 rpm...at that rate, any time my car is 'rolling' I'm already above the gains to be had by a responsive turbo and it's etra torque below useable area. In drag racing, most cars are leaving at 4000+ on slicks. Add LC, and now the turbo is already spooled, furhter negating the benefits of stock cams. Drifting is all about high RPM 's, and even when you look at how a car works on the street, you're never going to 'go' at 2500 rpm ya know?

(whew sorry for being long winded, I Just like car discussion...it's neat to get differing thoughts on the same thing, to furhter my knowledge :D )

Z U L8R

03-02-2010, 04:09 PM

@ mr_eh : you got a high hp set up....being that you're going 35r i can see that to you power is more important than boost response...therefore you should definitely get cams since you want the most power possible.

you guys get what i'm trying to say, and we agree on the most part.

my opinion , powerband > peak numbers

so i'd rather have my rb25 make 350+ ft lb of torque at 3500 rpm and make 440hp, than make 350ft lb at 4200rpm and make 460-470hp.

again i'm generalizing but speaking more specifically to lightly modded 240 guys who stress response and are lagaphobic, not us crazy bastards where it's either stock or 2,000 hp lol

good stuff =]

Dave

codyace

03-02-2010, 04:51 PM

Well that's my whole point - a cammed SR, even in close to stock form, will have a better average power and pwoerband than a non cammed one. I'd take a cammed stock car, than push 14psi through the t25 to create the same power.

Pacman

03-02-2010, 04:55 PM

It may be my missunderstanding, but aren't cams suppose to be degreed to make the most power and perform as intended?

MandTPhotography

03-02-2010, 05:36 PM

This is a good thread...

Def

03-02-2010, 05:54 PM

If you want more than ~300-320 rwhp on an SR then get cams. The flow through the valves with stock cams is in a choked flow(sonic velocity) too much of the valve event at that power level.

You can easily go from something like 320-330 rwhp with something like a 3071R to over 400 rwhp with just a set of "mild" 256 or 264 cams and lose only a little bit of bottom end in comparison to the top end power.

Below this power level there really isn't a reason to put bigger cams on an SR.

Z U L8R

03-02-2010, 06:06 PM

It may be my missunderstanding, but aren't cams suppose to be degreed to make the most power and perform as intended?

they can be when you have adjustable gears.

which is totally impractical for an sr or other similar timing chain motors. but even on a timing belt motor when you're adjusting the cam gears, you never really make MORE power than what they do...you're simply moving the powerband....granted you can start off and have the gears adjusted wrong, then fix it and pick up some power from fixing it but once it makes the most numbers it's gonna make, you're just left wasting time on the dyno moving the peak numbers around the rpm range.

as far as putting cam gears on a timing belt motor....if you're deleting vvt, then DEFINITELY not a good trade off.

adjustable cam gears are the most worthless "look what i got that does absolutely nothing significant for the money they cost" mod you could ever do...aka "rice" imho.

it'd be the same people that get adjustable cam gears but not spend the money on an electronic boost controller which has fail safes so you don't over boost.......that shit frustrates the hell outta me lol.

"you can lead a horse to water but you can't make it drink"

i don't like aftermarket cams on boosted motors, as you can probably gather from why i made this thread in the first place lol

i will always rock the stock cams for as long as i possibly can....and if i do upgrade, i will upgrade as mildly as i possibly can for the intended purpose of the upgrade, however i know what the car's gonna do when i put em in, some people don't, which is why i made the thread.

as far as a t25 on ANY car, there's NO lag there anyways and the turbo's so tiny it becomes a restriction at high rpm anyways, but i'd put a t28 on there way before i spent the same money on cams.

Big Ass cams on anything but a motor making Big Ass power is a Big Ass waste of money in my opinion

big ass cams are TEH SUX! :D .... unless N/A...then they are TEH SEX!.....with naaaaaawwwsss!

good point @ Def

whale's vagina Cody :P (it's from Anchorman)

Dave

codyace

03-02-2010, 07:06 PM

they can be when you have adjustable gears.

I absolutly 100 percent think cam gears are a waste of time on SR20. I've never seen any positive gains from them anywhere.

it'd be the same people that get adjustable cam gears but not spend the money on an electronic boost controller which has fail safes so you don't over boost.......that shit frustrates the hell outta me lol.

Oh god I agree. I ove when people tout how well their MBC works, and that EBC are junk....until they ride in an EBC car. It's a requirement IMO for a turbo car.

i don't like aftermarket cams on boosted motors, as you can probably gather from why i made this thread in the first place lol

But you gotta admit, there is a certain point (300hp I'd say) where you are really fighting aginst yourself using stock crap. You're not utilizing their flow ability, and essentially choking the motor. Again, even running a 260 duration cam on a stock t25, regardless of how restrictive) still puts it nearly 3-5 mph faster trap speed wise...that's a significant gain.

however i know what the car's gonna do when i put em in, some people don't, which is why i made the thread.

For sure. Cams themselves are a lost art if you ask me in the import world, and it's a shame so many have disregarded their importance with our stuff.

I'll stick to my guns forever with my 'guide'

JWT S3 or Tomei 260 for T2 flanged turbos
JWT S4 or HKS 264 (SII) for T3 flanged turbos
JWT C1 or HKS 272 (sII) for T4 flanged turbos.

Nothing boggles me more than guys that throw 272 in a little turbo car (DSM guys come to mind) and wonder why the powerband sucks...well duh!

Big Ass cams on anything but a motor making Big Ass power is a Big Ass waste of money in my opinion

To a point, but many BIG cams on any motor sacrifice a ton of low end versus gains in the big end. Look at some of the TexasSpeed cams for LS1's for example...great peak, but less midrange than stock...go figure haha.

whale's vagina Cody :P (it's from Anchorman)

Come on Dave, I heard San Diego is great :D :bowrofl: :bowrofl:

Z U L8R

03-02-2010, 08:05 PM

:D great epic movie!

i'm watching trashy whores on "bad girls club" .... wow

my gf loves this show....

yawn....

Dave

smelly240

03-02-2010, 10:38 PM

264/272 HKS step 2s are a fantastic setup for a larger turbo (30r or 35r)

I used 264s before this and up top i picked up a considerable amount changing to staggered - with no real losses down low.

martin has made about 600whp and 500tq with that setup -

i just changed to a VE head so i hope to get up to that 600ish area. waiting on one stupid part and i can go have fun... and just my luck the car goes to the body shop friday and the part comes next week.

eklips3

03-02-2010, 11:48 PM

i agree 100 % with you here dave.

cams are gonna be my very last step after all my mods that i have now

CrazyRob

03-03-2010, 12:23 AM

Z U L8R

03-03-2010, 06:47 AM

boost is the pressure of the air that isnt going into your cylinders. airflow is what you want, not boost... cams are more airflow. cooler airflow means more aggressive ign timing=more power=lower spool=more power everywhere.

imo cams and proper tuning should be a first mod.

"airflow is what we want", i agree totally.

"cams are more airflow"......kind of...and at a different rpm range

"cooler airflow means more timing" cooler air flow means you can add pressure, or temperature, so yeah you COULD add ignition timing. but cam's themselves don't cool down the intake air temps.

more aggressive ignition timing does make more power, to a point. once you reach maximum brake torque (mbt) for a given rpm, that's it. advancing the ignition timing beyond that is just adding more pressure on the top of the piston before it reaches tdc, increasing your chances of detonation, and actually decreasing your torque when advanced too far.

when you increase pressure you need to decrease temp or raise octane to maintain the balance. soley putting in cams alone does not do this. this is the laws of nature, physics, not my opinion.

http://upload.wikimedia.org/math/4/3/f/43fa535941b0be935b3b173e1ce20338.png

where p is the absolute pressure (http://en.wikipedia.org/wiki/Pressure) of the gas; V is the volume (http://en.wikipedia.org/wiki/Volume) of the gas; n is the amount of substance (http://en.wikipedia.org/wiki/Amount_of_substance) of the gas, usually measured in moles (http://en.wikipedia.org/wiki/Mole_%28unit%29); R is the gas constant (http://en.wikipedia.org/wiki/Gas_constant) (which is 8.314472 J (http://en.wikipedia.org/wiki/Joule)·K (http://en.wikipedia.org/wiki/Kelvin)−1·mol (http://en.wikipedia.org/wiki/Mole_%28unit%29)−1 in SI units (http://en.wikipedia.org/wiki/SI_unit)[4] (http://en.wikipedia.org/wiki/Ideal_gas_law#cite_note-3)); and T is the absolute temperature (http://en.wikipedia.org/wiki/Absolute_temperature).

when you raise one part of the equation, you need to lower another part of the equation, otherwise you lose the = sign

the goal is to run the the least amount of ignition timing you have to in order to make good power per your motor/setup. every motor's different and you have to balance what the motor will tolerate vs what you want it to do. without that balance, it's only a matter of time before you find the weakest link.

just because you increase the duration of the camshafts on a 2.0 liter motor, you're simply changing the time (rpm) of when the motor breaths the most efficiently. however you're not changing the displacement, it's still a 2 liter motor.

as a rule of thumb, just because you increase the cam duration doesn't mean you can, or should run more ignition timing. so i disagree with that statement. changing mechanical timing doesn't warrant changing ignition timing. the two are totally different, they just share the same word, "timing"

as far as profiling the cams goes. back in the day when cams were custom ground, there was a lot of variance and imperfections and what not. now that 95% of cams are made on a CNC machine there's a lot less imperfection and they're already pretty close to perfect. but again you need to have some form of adjustability to do that and you need to know the math & purpose for doing that cam in the first place, as well as plot out what intake centerline would be optimum for your motor, the cam you're using, and what you'll be using the motor for.

then we also need to specify that we're talking about cams on boosted motors and not n/a motors because the cams are TOTALLY different.

rule of thumb is cams on a boosted motor, especially the exhaust cam is gonna be pretty mild in order to keep exhaust temps higher to spool the turbo better. on a turbo motor your POWER is not coming from displacement as it's coming from the turbo's ability to create pressure. therefore the primary objective is to run boost and run it efficiently. which means making and holding boost as efficiently as possible. therefore picking the right turbo is waaaaaaay more important than slapping a big ass cam in the motor that's definitely lacking in the turbo department.

for my 2j 240z i may even leave the usdm turbo exhaust cam and upgrade just the intake cam only, or i may leave the stock ones in all together depending on how the motor performs. however i promise i won't just slap a set of cams in there first without knowing and understanding what my motor's doing and why i'm putting the cam in there, again why i made the thread.

we can even discuss, in my opinion the "uselessness" of big ass cams on a bone stock head.

we all know motors have a bunch of different things on them, all with a job, all working together to achieve a set goal.

the job of a cam with a bigger profile and longer duration is to hold the valves open longer and change the mechanical timing efficiency of that same 2.0liter or whatever motor. however without changing the displacement of the engine, without changing the swirl effect of the combustion chamber (head), without changing the ability for the valves to seal (3, 5 angle valve job), and without changing the ability of the head to flow air more efficiently (port/polish) you're still falling short and only addressing one piece of the puzzle comprised of many pieces.

we should never just slap parts on our motors without understanding how those parts are going to affect it.

lets say you're starting out with an NA motor THEN boosting it, for example, going ka-t.

my opinion of the usefullness/uselessness of cams here changes greatly. once the TURBO "kit" with all the supporting mods are thoughtfully installed to meet it's intended goal, then i'd totally put some mild "turbo" cams in it, expecting and gaining a substantial increase in power and efficiency.

great discussion :)

Dave

fliprayzin240sx

03-03-2010, 07:05 AM

If this was only explained to me in lay mans term like this a year ago...I wouldnt be driving with Tomei 270s. I should have gone down to 256/264 stagger...

nismo tuned s14

03-03-2010, 10:12 AM

Z U L8R

03-03-2010, 10:22 AM

I could tell a world of difference with JWT 275s on my KA24DET. It was the last mod I did to the engine. It's fully built. I haven't dyno'd it yet, but I could tell a huge difference mid range to top end. Maybe it's just a KA thang..

absafrickinlutely!

right on man =]

the stock KA (N/A) cams are totally different from turbo cams so even though 275's are hyuuuge lol in my opinion getting the correct type of cam for your motor since it's now boosted would DEFINITELY help performance.....and it sounds like it did. ^_^

case and point.

Dave =]

chituntang

03-03-2010, 11:11 AM

Stop talking about trap speed, or any drag race thing because you are not really using your powerband. You put your feet on the gas pedal, and get it to the shifting rpm, then shift. You will not have your engine reving at like 2.5k rpm.

Now I am not saying drag race sucks, but looking at those 10000000+whp Civics with those have big turbos, this is the thing Dave is saying. You want to hit that 1000000000whp within less that 1000 rpm at the top, or have the turbo fully boost up at a lower rpm and hold it for 4000rpm.

This is why things like vtec, vvt, vel, etc are with us now. When early technology like vtec is like having big cams at high rpms only, technologies like vvt makes new engines with no better power range, because it can adjust its cam to the best position.

Since SR's (well, the S13 SR) cannot do any of it, you can only choose a section of the rpm where you can maximize your power. And this is what Dave's talking about here.

jspaeth

03-03-2010, 11:12 AM

more aggressive ignition timing does make more power, to a point. once you reach maximum brake torque (mbt) for a given rpm, that's it. advancing the ignition timing beyond that is just adding more pressure on the top of the piston before it reaches tdc, increasing your chances of detonation, and actually decreasing your torque when advanced too far.

dave, I agree with you wrote here, but in THEORY the ignition timing that gives MBT could itself be a function of HOW much air is coming into the engine at a given RPM, as well as the air's temperature and pressure

Thus, in theory, optimum ignition timing at a given RPM probably changes when you change cams.

(I don't have ANY experience tuning cars, but this seems reasonable based upon my physical intuition).

Z U L8R

03-03-2010, 11:35 AM

there's more to that :D

and i'll respond later when i have more time. i have to diagnose this stupid jeep grr lol

Dave

mr_eh

03-03-2010, 12:18 PM

oh it's a twin scroll 35r i think it should start making power a little bit sooner to warrant the 264/272 setup

spooled240

03-03-2010, 01:06 PM

I kind of agree with this, but I think it depends on how the car is driven. If it's seeing 7K rpms drifting and drag racing then I'd say fuck the low end..but for a daily driven street car that's mostly going to see about 3K rpms, low end is going to be used about ALL the time.

i have a daily driven s14 ka-t running about 8-12psi of boost (240-280whp) on the stock 232's and my power drops off around 5700 lol, low end torque around 3K when the turbo spools is a monster though

I'm thinking about swapping to the s13 cams, since I don't wanna lose much of that low end torque..so I'll still be on stock cams persay

CrazyRob

03-03-2010, 03:01 PM

i think the thread title should be "my .02 on cams for brainlessly tuned boosted motors"

for drift, drag, and circuit having top end power is key while not sacrificing torque at the low end. in my opinion a motor should be tuned to the transmissions difference in rpm per gear. pretty much when you upshift the motor should be just past where it torque band kicks in. if you can afford a boss transmission you tune the engine however you want and change the trans to suit the powerband. with most peoples applications i would raise the redline and make sick top end power then change the diff ratio to keep the same mph per gear while making the engine not work so hard to get there. cams and turbo selection in a boosted motor comes down to what the cars overall setup will be.

on a street car racing style top end matters very little and on-demand passing power is king. so depending on the the hp/turbo efficiency/rev limit/headflow cams could be a good option for a boosted motor.

if someone is serious about racing, cams and tuning should be a first upgrade besides full cooling system upgrades.

if someone is serious about daily driving passing power they should increase their boost and leave their cams for a near last mod.

imo.

Z U L8R

03-03-2010, 04:26 PM

dave, I agree with you wrote here, but in THEORY the ignition timing that gives MBT could itself be a function of HOW much air is coming into the engine at a given RPM, as well as the air's temperature and pressure

Thus, in theory, optimum ignition timing at a given RPM probably changes when you change cams.

(I don't have ANY experience tuning cars, but this seems reasonable based upon my physical intuition).

i agree with you :D. however, optimum ignition timing sometimes has to come second to allowable ignition timing. and in order to keep from blowing things up sometimes ignition timing does have to change when you change cams, i agree

down low to mid range power of this xyz aftermarket camshaft per say is gonna be less efficient than the factory turbo cams, therefore reducing hp and torque.

high mid to high rpm range the longer duration bigger lift is gonna be more efficient than the factory turbo cam. so it's going to allow the ingestion of more intake charge because it's holding the valves open longer, therefore to compensate for this slight increase in air you would increase the fuel (injector pulsewidth).

thus your major adjustment would be in the fuel tables to acheive your target air fuel ratio. as far as the ignition timing table, because you're at high rpm / high load you're not even truely able to get MBT ignition angle because with that added pressure something's gotta give or kaboom. so where this cam profile is shining you're only able to run enough timing to stay below your knock threshold. because your now weakest link is how much timing can be in the motor before the heat and the pressure cause knock/detonation.

as far as tuning the car, you need to balance that margin of safety of whether you should add fuel only, add fuel and add timing, or add fuel and take away timing. if you add timing and get diminishing returns, leave it alone cause it's safer to make a few less hp/tq than blow up the motor.

and in the same way, with these xyz aftermarket "turbo" camshafts, down low where this camshaft is less efficient than the factory turbo cam, you can increase the ignition timing to MBT because the cam's efficiency is lower. but that's really a given anyways because the VE is lower, the load is lower and all that.

so here's also where a car with cams and a stand alone surpasses the same car with just an air fuel computer because here where you're losing VE, you can try to optimize performance by advancing the ignition angle.

on a similar note. i've noticed that if you log the boost and do a pull, then do another pull this time with the ignition timing advanced a little more, it will not make as much boost, therefore indicating some truth to what your inclination was, [paraphrasing you] "that adjusting the ignition timing did somehow affect how well the motor flows the air....i will say though, that i've only noticed this when tuning a car that has the base timing too retarded. once i advance the timing to where it needs to be, then do the pull, the boost drops slightly.

why does this happen? well think about it. it's an engine, a big air compressor, would changing the ignition angle closer to optimum from not optimum increase it's efficiency? of course. but also advancing the ignition angle from too retarded is also lowering exhaust temperatures therefore not creating as much pressure to spin the turbine......for the most part though no change in boost theoretically should be noticed since boost is regulated by the wastegate.

would changing how long and when in the rotation the intake and exhaust valves open and close make the motor more efficient therefore requiring a change in ignition angle? Yes, no, but not necessarily. if anything a reduction in ignition angle may be necessary to avoid knock/detonation due to the added cylinder filling at that same tuning point as I explained earlier.

basically aftermarket turbo cams are just going to open and close the same exact valves a little longer and a little later/sooner than stock. the valves are still the same size. the ports in the head are still the same size. the displacement is still the same size. therefore you're basically borrowing power/torque over here, to make power/torque over there. that's it.

with things like vtec and vvt , you have the best of both worlds.

as far as stock turbo cams go. i'm not speaking for EVERY stock boosted engine because some boosted motors from the factory get really restrictive shitty cams. And some manufacturers build factory race cars. But for the most part the manufacturer's intent was drivability (street car first, race car second). most people's swapped cars are their daily first, and their race car second.

therefore intent and purpose should go into whether or not cams are a good choice based on the intent and purpose of your car. and that goes for EVERY mod on the car.

now on to NA cams.

The majority of factory NA cams are totally restrictive. this is because the motor's typically built around longevity, emmissions regulations, and the manufacturer's r&d budgets FIRST, then performance as the byproduct. then you go over to the more sports car minded NA cars, this will be less of the case and the profile will be a little more aggressive than it's commuter brethren, along with probably a better flowing intake and exhaust design.

however upgrading to a more aggressive NA cam will definately yield improved performance if the factory cam is restrictive...but again, there's a balance. when you get too crazy with the cam, then it's the same, you're robbing peter to pay paul, borrowing power here, to get it there.

and if going from NA to turbo, then totally getting a set of turbo cams will improve performance, as said earlier.

now truely, if you really want the power and efficiency out of those magical cams that just move the power around without any loss down low. increase your engine's efficiency. port the head so it'll flow more, do a valve job so they seal better, get a better exhaust and induction system(intercooler/piping included).

it's an engine, everything works together. but FIRST, it's a boosted motor, it makes it's power because it's turbo'd, wouldn't the best upgrade be a more efficient turbo? of course!

cliffnotes:

cam's rob peter to pay paul. I like Peter AND Paul (no homo) :)
parts on a motor work together to improve performance
i still don't like big ass cams ;)

if you WANTED Paul to have the upper hand then your cams did exactly what you wanted them to do and there's no reason you should feel bad, you did the right thing!

disclaimer:

don't go cranking up the ignition timing down low just because your cam's not doing shit down there. Don't blame Dave for irrational/non-observant tuning methods lol. MBT is MBT.

Dave :D

jspaeth

03-03-2010, 06:38 PM

wow! informative hahah

codyace

03-03-2010, 08:03 PM

264/272 HKS step 2s are a fantastic setup for a larger turbo (30r or 35r)

I used 264s before this and up top i picked up a considerable amount changing to staggered - with no real losses down low.

You'd gain more with straight 272 and cam gears if you're looking to play with the intake side of things. Again, you need to look at lobe separation angle when it comes to 'turbo' setups. Obviously as close to zero is best, yet a big seperation helps with response (while killing top end). With a car that uses a huge turbo, I'd shoot for the lowest LSA, rather than the bigger gap for response.

VVL heads are great -- I have little experience with RWD, but in FWD they are a gift. Obviously most setups also involve a full point of compression, but the flow characteristics remain the same. awesome stuff. But for 600 whp, I would much rather go with displacment, rather than boost...just my preference though. Nissan certainly isn't giving me any trophy for doing well with their shiz.

Stop talking about trap speed, or any drag race thing because you are not really using your powerband. You put your feet on the gas pedal, and get it to the shifting rpm, then shift. You will not have your engine reving at like 2.5k rpm.

Trap speed is the single most important indicator of how well a car accelerates, drag race or not. When you measure 1/8th to 1/4 trap differences, or sectional speeed increase, you can get a true indication of how 'quick' a car is in the setup. Drag racing in the overal scheme of things may be lame to you, but the physics aspect it something you can't deny - a faster car will trap faster. Bottom line, if you trap higher, the car is faster. I mean, its' just how it is. Think about it:

a 300 hp car with stock 4.08's does XXX speed
a 300hp car with 4.6 FD does faster. Sure it may be slower to the 1/8th, but in all truth, 1/8th to 1/4 speed increase is the single best indicator of how fast it will be on track, or on street.

thing Dave is saying. You want to hit that 1000000000whp within less that 1000 rpm at the top, or have the turbo fully boost up at a lower rpm and hold it for 4000rpm.

But the point is, i'm not arguing for the big hp small powerband cars...they are geared/tire'd to stay in the powerband. I'm saying that a cammed stock car will be faster than a stock cam car. And it's always the case.

Thus, in theory, optimum ignition timing at a given RPM probably changes when you change cams.

Correct. Timing throws everythign off in regard to max timing advance and all of that stuff.

I kind of agree with this, but I think it depends on how the car is driven. If it's seeing 7K rpms drifting and drag racing then I'd say fuck the low end..but for a daily driven street car that's mostly going to see about 3K rpms, low end is going to be used about ALL the time.

But realistically speaking, the only time you are below 3k, is pulling out from a lamp. The car idles at 1000 for all intents and purposes....just watch where our car's rpm's are pulling out. It's sure great to have the ultimate low end power, but you never really 'use it' for anything performance related. I could care less about daily driving, so lon as MPG stays up.
[/QUOTE]

down low to mid range power of this xyz aftermarket camshaft per say is gonna be less efficient than the factory turbo cams, therefore reducing hp and torque.

Again, 'turbo' specific cams are aimed at real deal setups. JWT S3 and HKS 264 are not 'turbo cams'....but they work awesome.

as far as tuning the car, you need to balance that margin of safety of whether you should add fuel only, add fuel and add timing, or add fuel and take away timing. if you add timing and get diminishing returns, leave it alone cause it's safer to make a few less hp/tq than blow up the motor.

Certainly - but adding boost is also a potentially dangerous solution to lack of airflow. You increase detonation ability 100%, which to me isn't worth it.

The least amount of boost and timign required to make XXX hp is the best, and that's why cams are the best addition IMO.

Again, I could care less abotu the 2500-3500 rpm power band. This area under the curve in no way helps in the grand scheme. Hell a car that makes 10-20 lessin the the 2500-4000 range, yet makes 20-30 more in the 4000-7000 range is always the faster car, both on street, on track, and in trap speed.

Again, traction is that 'lost' thing too...a car that makes more torque, yet rolls the tires, is slower. For example: my buddies Lightning is a fantastic machine (road races it, so it's all abotu down low)...but in a normal circumstance, he makes 'to much' power down load, and ends up rolling the tires off....when the car with a better average powerband stays ahead.

Response rocks - i"m addicted to it...but when it's at the expense of acceleration, I'd rather aim for the powerband.

basically aftermarket turbo cams are just going to open and close the same exact valves a little longer and a little later/sooner than stock. the valves are still the same size. the ports in the head are still the same size. the displacement is still the same size. therefore you're basically borrowing power/torque over here, to make power/torque over there. that's it.

While the general 'entry/exit' paths may remain the same size, the flow charecteristics and the combustion process are not. The most amount of air flow per constriction will net the most power. Again, a low end powerband does not indicate a stronger car. Look at v8's with RV cams for example.

and if going from NA to turbo, then totally getting a set of turbo cams will improve performance, as said earlier.

Totally untrue. Again, LSA is a very important part of turbo powerband. A larger duration cam, with a better LSA will do better than a shroter duration with a crappy LSA.

Again, average powerband always results in a faster car. You can ahve all of the trump extracting, house pulling, grin inducign torque and resopnse in the world - but a car with better average power will always win the race, turbo, N/A or nitrous.

codyace

03-03-2010, 08:12 PM

Lets not also forget the 'gear ratio' factor. Throw a hot set of gears in (4.3 or 4.6) and yo ucan get all the mechanical low end you want, and then use the big cams for the top end. Ooooh baby, what a nice combo.

Z U L8R

03-03-2010, 08:16 PM

good! mission accomplished!

what started out as an opinionated and frustrated rant, turned into a great discussion on cams.

Again, 'turbo' specific cams are aimed at real deal setups.
my point exactly.

San diego really is a nice place :) my little bro's stationed there on the U.S.S. Stockdale. i love pacific beach....i fell asleep at pacific beach for 15 minutes and woke up with all these hotties all around me tanning.....LOVE THAT PLACE! whale's vagina ftmfw

lol i know i'm a total car nerd...but i really am a sexy mofo, best watch yo girlfriend yo, i'll dazzle her with muh profile , lobe, and duration ya kno wha'msayin boiiiiiii!

how we do ATL style shawty ^_^ :bowrofl:

Dave

codyace

03-03-2010, 08:53 PM

i'm glad i don't watch that many movies - i usually fall asleep ;) but anchorman I watched

It's the same with any car type/engine type though- "turbo" cams are great for the 500+crew -- at that point those guy sknow what they are doing. For anything else, JWT S3 is best.

Z U L8R

03-04-2010, 06:35 AM

i also wanted to clarify a little on my OPINION for ka-t set ups.

yes you'd have EXCELLENT response on a ka-t by just leaving the stock cams, or putting the stock s13 dohc cams in it (if you had an s14 dohc ka24de), but torque and powerband up top would drop off because of the profiles.

also because a ka is a 2.4 liter, displacement and static compression are higher than an sr therefore doing cams would not kill your powerband down low because it's plenty torquey. but EXACTLY the mildest 'turbo' cam like the s1 cams in my opinion would be a perfect choice because they barely impair down low (where by design it's already strong enough) but DEFINITELY help the motor breath better up top.

i personally haven't tried the s1 cams in comparison to stock but like i said, once all the other important details of my ka-t build were dealt with. if i still wanted more out of the car, i'd definitely start seeing what i can do to keep the powerband from falling off up top by experimenting with some different cams. obviously if the s1 wasn't a big enough difference, then i'd go bigger.

from experience i'll say that i wouldn't have peace of mind with pushing a stock ka bottom end passed 10psi, therefore i would have my own at 8 or 9 psi tops, and it'd last no problem. once i built the bottom end with forged pistons and rods, the added thickness of the ring lands of turbo pistons vs the n/a pistons as well as the strength of the material and cooling properties of them, i'd have no problem cranking that sucker up and puttin down some worthy power.

i know there's guy's on ka-t.org making 9 million horsepower on the stock bottom end and running 40 psi and what not....but they have the magical ka-t juice that only the magical leprechaun triplethurodon on the top of candy mountain possess. us regular folk don't have access to such marvelous wizardry so we're stuck obeying the laws of physics and properties of metals...;)

in the ka's the pistons are the weakest link, the rods and rod bolts are the next, therefore if you do one, do the other while you're at it, and have an overly stout set up that you can run at 50% of what it can handle, and that's how you'll get your fun out of it without blowing motors up every other month.

there are exceptions to every rule and everyone has that buddy that's running 15psi on a stock ka-t for 2 years with no problem....but in my experience, he's the exception, not the rule.

"seems like there's always enough time to do it twice, but never enough time to do it right" -Tim Coleman-

Cody thanks for being "devil's advocate" but definitely making some good points along the way. we're both saying the same thing for the most part is what i'm concluding.

Cody: my opinion on a turbo car is , less valve overlap is most desirable as it causes reversion, n/a car obviously more overlap is more desirable. how do you feel about that and elaborate in lay man's terms so other's can follow along.

also as Mr. Corky Bell talks about in his must read book
http://img135.imageshack.us/img135/8827/maxboostgg9.jpg

he talks about in the latter chapters where you're actually testing your set up. checking your exhaust pressure in comparison to your intake pressure. for a street car a 2(exhaust) to 1 (manifold pressure) ratio is ideal, however for a full race set up 1-1 is the goal.

by basically checking the pressure's and comparing them at your torque peak vs redline, you can see if you have a properly matched turbo on your car.

if you have a shit ton more pressure in your exhaust before the turbo than in your intake manifold then you can deduce obviously that your turbo's too small, a restriction, and the reason torque/power falls off as rpm increases. good example, t25 turbo at 14psi........(technically they don't hold 14psi at redline tho lol)

but here the restriction is the size of the turbo, NOT the cam shafts. just running a bigger turbo at lower psi will flow the same air to match the power down low, and be less of a restriction therefore freeing up the hp/tq up top.

this was the point i was making in context. upgrading the turbo as first priority addresses the size of the turbo being a restriction. upgrading the cams and leaving the turbo the same takes away even more usable power down low and though will make slightly more up top, still doesn't fix the restriction. it'd be like changing to a wider rim when your problem remains that the tires aren't balanced.

but the point is, you're losing power down low AND still running the same boost versus losing a little down low for the spool difference, but gaining efficiency, therefore able to make the same peak numbers as before, with better powerband up top at lower boost. obviously if you crank it up to the same 14psi you'd make even more power than before.

the other GREAT points Corky makes is about your intake system and intercooler piping. you can test for pressure drops after the air filter or after the maf and see pressure drops. these pressure drops force your turbo to work harder to move the same amount of air. therefore the pressure (psi) has to increase in order to flow the same amount of air, and with that pressure, comes more heat......totally the things we're trying to avoid.

same goes with checking your pressure drops in your intercooler and piping, even with throttle body. you can actually KNOW, test, and find out restrictions in your turbo set up to increase your set up's efficiency, and THAT'S how/why good and properly matched parts make all the difference.

a 2psi loss is tolerable. and 0 loss is impossible :P

woot woot

gearing is totally frickin AWESOME as well. the stock r200 diff in the 280z's are a 3.54 if i recall correctly (iirc), i was running an 83 280zx 3.9 open diff. i ran [email protected] 125mph on 245/60/14 bfg t/a $50 s-rated pep boys tires with 1 wheel spinnin and a mighty suck ass 2.1 60 foot hahaha. my 4th gear would tap out at 120mph so right at the end of the 1/4 i had to shift into fifth.

just for shit's and giggles i put the stock 3.54 back in, now 4th gear went to 140...then there was fifth...keep in mind my tires were only rated to ~100mph.....scarey thing i tested this out indeed >_< (dumb ass)

went back to the track, and ran a 11.95 @ 122mph with a 1.99 60' . as far as the dyno sheet, boost kicked on about 300rpm sooner. but since i didn't spin as much on that pass the trap speed went down. i hated the stock 3.54. the same modded c6 z06's that i'd race with the the 3.54 i'd be dead even with, where as with the 3.9 i would beat by 2 cars. i quickly switched back to the 3.9.

ideally the z31 88 turbo 300zx has an r200 3.7 vlsd. i think that would have been the best compromise. not only was it the only direct bolt in lsd, but i could wind out 4th gear a little passed the 1/4 mile and eliminate that last shift.

all in all though, with better tires, if i could drop my 60 foot time to like a 1.6, the car would've probably done a 10.8-11 flat no problem based on the trap speed. every tenth off your 60 foot time is 2-3 tenths off your 1/4 mile.

i'm totally not a "drifter", but drifting is fun as hell....i prefer hwy pulls or the drag strip.

i just like the look on the face of the dude in the mercielago that got spanked by a 30 year old rattle canned datsun mauhahahaha.

i gotta keep this post semi 8 page, cause i gotta knock out this timing belt water pump on an elantra! YAAAAY!!

what's your thoughts "ProjectRDM" mr. RUSS!?! HRMM ^.-

Dave

Z U L8R

03-05-2010, 11:37 AM

since we're on the discussion of cams, this is a FANTASTIC, how to on degreeing cams etc.

check this out when you get time.
www.ka-t.org :: View topic - How To: Setting Valve Lash/Dialing in Cams (http://www.ka-t.org/forums/viewtopic.php?t=41963)

that's that ka-t wizardry right thurr ^_^

Dave

SrRaycer

03-06-2010, 09:19 PM

Overlap can be tuned with cam gears. Some of you are talking as if stock Nissan cams are magical. Talk about the stock cams lift and duration vs aftermarket options, all aftermarket cams aren't made for peak power, hence all the options available. There are cams made specifically for torque and midrange that outperform the stockers in the "usable powerband" department. WHAT about the stock cams make them the BEST for torque and spool?

Z U L8R

03-06-2010, 11:09 PM

low lobe separation angle (LSA), which means low overlap as well as they have low duration as high duration and low LSA still creates more overlap. the design is around driveability and midrange power, as is the turbo that comes with it.

it's not that the stock cams are magical, and it's not that aftermarket cams are either. it's just that until you get rid of your biggest restriction in airflow and power which is the itty bitty turbo, there's no point in putting cams in there that are gonna still be restricted by the output of this same itty bitty turbo.

upgrade the turbo and do all the other supporting mods, THEEEN tweak the power band with some cams if you want to.

cams definately have their place and use in the scheme of things, there's just a lot of other more important things that limit the engines power output that should be dealt with before the cams need to be.

cams are more like the final touch to the engine build. the icing on the cake if you will. the proper cams will compliment the already thoughtfully upgraded turbo system.

if it's between upgrading the stock turbo versus the stock cams....deal with your weakest link first.

that's where my emphasis is.

Dave

SrRaycer

03-07-2010, 12:02 AM

The point is you can't say they aren't necessary unless your trying to "tweak" the powerband for a few additional hp. They may not be necessary for YOU and your driving style as everyone doesnt like to rev, but some do. Isnt that what makes vtec in hondas fun? nobody complains about that. Some of us dont need full boost at 3200 and would like a higher powerband that hauls all the way to 8k+...
And you're supposed to match your cams to your turbo,there is a LOT OF MISINFORMATION AND OPINION being labeled as fact.

You keep mentioning should you buy cams vs an upgraded turbo or something, I am talking about whether aftermarket cams can be an improvement over stock for a responsive setup...you seem to be talking of a budget build.

Z U L8R

03-07-2010, 09:57 AM

"I am talking about whether aftermarket cams can be an improvement over stock for a responsive setup" -SRRaycer-

the answer is no.....the only thing you could do is go even less LSA and less duration....then you WILL be getting into restricting power with changing the cams.

the reason hp and torque fall off up top with the stock sr20 set up is because of the turbo, not the cams. that's not my opinion, that's the facts.

the purpose for upgrading the cams is to help maintain power and torque at mid to high rpm....but when the size of the stock turbo is the reason your hp/tq is falling off...address the reason FIRST.

lol i dunno what else to tell ya sir. it's not about a budget build, it's about making intelligent decisions for modding your car.

what good is upgrading to a 3 foot carbon fiber racing spoiler when you're still running the stock engine and need to change your oil?

sure, spoilers have their role and purpose in the grand scheme of things...but aren't there more important things you can spend the same money on before you get a spoiler? if you're getting a spoiler because you want to grip the road better, then wouldn't a better upgrade FIRST be better tires?

that's my opinion. if my opinion is completely illogical, that's your opinion....and we can disagree, no biggie :)

"san diego means whale's vagina"

Dave

SrRaycer

03-07-2010, 02:47 PM

"the purpose for upgrading the cams is to help maintain power and torque at mid to high rpm....but when the size of the stock turbo is the reason your hp/tq is falling off...address the reason FIRST." Z U L8R

You still seem to be talking about cams vs turbo. I understand that your saying upgrade cams when you have the appropriate turbo, but you also seem to be saying don't upgrade your cams with a bigger turbo so you can still have some low-end power.
I think this argument will just go back and forth so I give...lol

But I still stand by what I previously posted

codyace

03-07-2010, 03:36 PM

from experience i'll say that i wouldn't have peace of mind with pushing a stock ka bottom end passed 10psi, therefore i would have my own at 8 or 9 psi tops, and it'd last no problem.
--
i know there's guy's on ka-t.org making 9 million horsepower on the stock bottom end and running 40 psi and what not....but they have the magical ka-t juice that only the magical leprechaun triplethurodon on the top of candy mountain possess. us regular folk don't have access to such marvelous wizardry so we're stuck obeying the laws of physics and properties of metals...;)
--
there are exceptions to every rule and everyone has that buddy that's running 15psi on a stock ka-t for 2 years with no problem....but in my experience, he's the exception, not the rule.

I wholeheartedly agree with this. When I see these guys and their magical '300 hp all day no issue' steups, I really question how 'driven' they are.

While my 240 experience is 95% SR related, I will say that my 'turbo nissan' roots were in my fun little 1994 Altima...that I turbocharged - what a great setup, and at the time (2002/2003, there weren't many turbo 'anything' out thrre (aside from DSM)...so an aftermarket, custom, turbo ALTIMA was super uncommon.

Our rule of thumb was, 10 psi - or 12 if you trusted the tune and didn't care if it blew up. Needless to say, my car lasted roughly 10,000 miles before my brothers blew it up once they raised the boost to 15(when I was deployed).

Nice to find someone else who realizes this. PS: 'Leoplurodon' was the magical dinosaur haha.

Cody thanks for being "devil's advocate" but definitely making some good points along the way. we're both saying the same thing for the most part is what i'm concluding.

Cody: my opinion on a turbo car is , less valve overlap is most desirable as it causes reversion, n/a car obviously more overlap is more desirable. how do you feel about that and elaborate in lay man's terms so other's can follow along.

No problem - I too think we're talking about the same thing, just go about it two different ways - there is always another way to 'bake the pie' as they say.

In regard to overlap, obviously the least amount = best 'technically' (and as you mentioned helps reduce backpressure ratio). BUT in the same response, that 'overlap' is also what helps make better average power. Certainly, there is no denying the fact that less overlap helps spool the turbo better -- but with anything, this 'spool up' positive, comes with a negative: lack of a 'hearty' powerband.

For me, unless I was making a 'race car', I wouldn't bother with striving for cams with less overlap/backpressure for a street car. I'm certain my ratio is near 2:1, but so long as your tune is safe and you don't run a bunch of timing, you really can't go wrong with it.

also as Mr. Corky Bell talks about in his must read book

Maximum boost (to me) is like the first testament of the bible. Great start, got the basics, and generally speaking - but it is severely out dated at this point. The concepts will forever be there, but with the advent (and accessibility) of better parts, tuning solutions, and shops, have also come new ways to approach the issues.

but the point is, you're losing power down low AND still running the same boost versus losing a little down low for the spool difference, but gaining efficiency, therefore able to make the same peak numbers as before, with better powerband up top at lower boost. obviously if you crank it up to the same 14psi you'd make even more power than before.

lets also not forget the often forget, and overly (if not the most) important issue surround dyno graphs: lack of a standardized graph OVER time. Sure a graph could look perfect, but if it's slow to respond and comes into power sluggish, that nice powerband really is nothing more than 'eye candy' to impress people on forums and car shows. When I look at my graph versus others (as well as other SR cars) in WinPep, trying to figure out a standard 'overtime' point, it's really evident. Sure those those steamy t28 graphs with full spool before 3000 look impressive, and seem fun, but once you look at the graph over time, you'll see how much that lack of top end really hurts, as it's SLOW SLOW SLOW at that point.

So with anything, racing dyno graphs is certainly an interesting tool, but with so many differences in dyno type, load application, and correction - they should always be taken as examples. Strap my car on a mustang dyno and throw a load on it, and it'll spool like the street. On our dynojet, it spools later, but is much more repeatable in power. Which one is best? Depends on who you ask. I do know this though, the 'non load' factor is a best crappy for setting boost up on, as on the street you almost always see more.

the dyno sheet, boost kicked on about 300rpm sooner. but since i didn't spin as much on that pass the trap speed went down. i hated the stock 3.54. the same modded c6 z06's that i'd race with the the 3.54 i'd be dead even with, where as with the 3.9 i would beat by 2 cars. i quickly switched back to the 3.9.

The spool increase was from the extra load through gear, for those not understanding that aspect. Remember, load = turbos best friend at times.

BUT, one advantage of a small turbine is that they light fast, and are predictable. Hehe, I run a 4.6 - sure I loose some spool torque, but the mechanical advantage >*

army240

03-09-2010, 07:59 AM

Thanks a lot on this fantastic discussion on cams!

What do you guys think about stagered cam setup? I'm about to install HKS 256/264 (int/exh), 10.5mm lift, on a stock internal, stock head, tomei expreme manifold, HKS GT2540, all support mods, on a friend car...

I ran the number throught the calculator on the KA-T site, here's what it give :

Overlap : 4.00 degrees
Intake Duration : 222.00 degrees.
The Exhaust Duration : 225.00 degrees.
The Inlet Cam has an Installed Centerline of 108.00 degrees ATDC.
The exhaust cam has an Installed Centerline of 111.50 degrees BTDC.

I've seen some nice dyno sheets with the stock intake cam, and BC 264 on the exhaust side, with T28... Not big number, but nice powerband all along the RPM range.

Anyway, i'm just curious what you guys think about stagered cam setup!

And again, this is a really interresting discussion!

Frank

Z U L8R

03-09-2010, 02:09 PM

army240

03-09-2010, 03:19 PM

give it a shot Frank, if you can post up dyno graph at the same psi before and after and the only difference being the cams/tune then it'd be great to see your gains and how the motor liked it.

i'd give it a shot. nice/expensive turbo too btw :D

Dave =]

Unfortunately, I won't be able to do a "Before" dyno sheet, cause i'll be installing the HKS at the same time as the cams(now it's on a S15 T28). Also, the engine is already out of the bay, and I don't have any dyno sheet. But I will surely post a "After" one ;)

As with the discussion, I say that they're a lot of mods I would do before putting aftermarket cams in a stock SR. As for choosing which cam, I guess that's a lot of research, and it depends on what you want! Big number, or nice powerband... you choose, you can't really have both I guess!

Frank

P.S. Like I said, this is my a friend car I'm working on... I wish I could own his turbo haha!

jspaeth

03-09-2010, 03:37 PM

As for choosing which cam, I guess that's a lot of research, and it depends on what you want! Big number, or nice powerband... you choose, you can't really have both I guess!

That's partially true....I would say having a "nice powerband" means having a relatively wide and flatt-ish torque curve.

If you start going with bigger turbos like a 30R or 35R, you NEED the bigger cams to help the motor breathe up top and you NEED headwork to raise the limit to AT LEAST 8000 RPM to even make it worthwhile.

The torque curve on my 2871R with 264/264 starts to drop off around 7000 RPM or so, maybe a little earlier.

I bet with a twinscroll 30R and 264/264 with the Greddy Intake mani, you could have a setup that spools early and makes 350 ft-lbs from 4000 RPM-7500 (8000?) RPM.

Now THAT would be a sick powerband.....

My buddy is running a 30R on his S2K.....it is retarded.....he makes solid torque from like 4500-8200.....

Z U L8R

03-09-2010, 05:55 PM

ya, when i was at Lethal we put a 30/76r on an 06 s2000 (2.2L) and that thing was like insta spool, it was great.

honestly if i get to baller status once my 2j 240z is done and making 600hp i'll be going back to working on my ka-t datsun 510....i only want 400-450 outta that now since the Z can be my corvette killer, but if that ka blows up, it'd be bad ass to put an s2000 motor in the 510. uber rev, 6 speed, strong as hell motors (cept for the gay open deck block), and best of all boost AND V-ATTACK!!! lol

honda definately has the best flowing heads. of course that's what million's of dollars in R & D will get you :) they won't TELL you what they did, but it'd definitely be wise to COPY what they did ;)

this definitely isn't a "closing statement" as i still wanna see more people's before and after dyno sheets of cams.

i'm glad i made this thread, and thanks everyone who posted in it.

keep it alive! post up your dyno sheets if you have any before and after just cams if you can, and make sure you give us a brief description of your set up, how much boost, and what cams.

thanks,

Dave

renegade_ewok

03-09-2010, 10:29 PM

This is a hell of a thread...

Im chiming in on this cam discussion - Im running a T28 with HKS cams (256/264 split duration... at least thats what the timing chain guide had etched into it...) and the T28, down low, is a touch less responsive than an OEM cammed SR. I drove another SR and it felt more torquey <3000 RPM, but after that my car with the cams felt like it PEAKED higher in the mid range. I have no charts to compare unfortunately.

redpotatoes

03-21-2010, 02:03 PM

there are exceptions to every rule and everyone has that buddy that's running 15psi on a stock ka-t for 2 years with no problem....but in my experience, he's the exception, not the rule.

I guess I am an exception because I am running 15psi on my stock block and it's running like a charm for the past years. A proper maintained engine and a good tune makes all the difference.

Pacman

03-23-2010, 06:21 PM

Going back to my post about the adjustable gears, like you said later in the thread about making power here and losing there, the gears can bring power back into a more usable range, or bring power where it wasn't before verse just slapping cams in. Brings the power band back where its usable. Thats where I'm going with this.

Think like 248/248 swap on a KA, it makes power (I remember seeing the dyno of the comparison a LONG time ago) but its so high in the top end. Having the power that high is pretty much useless unless you sit at 5500+RPM all day. Timing them allows the cam to function as the designer wanted and makes the power come back to useable. I feel gears are good to have, not necessarily manditory, when upgrading cams. (Am I making sense or is the Norco clouding my mind [knee surgery]?).

Awesome thread. Read through the whole thing.

army240

03-24-2010, 08:03 AM

jspaeth

03-24-2010, 08:31 AM

Adj. Cam gears are a good thing to have... give you flexibility for your application. If you have the budget for it, it's not a bad thing to have. BC 272s recommand using Cam gear, i'm using them, degreed to true TDC. With stock cam gears, idle is rough and there's low vacuum. So it's a good thing to tune them.

Frank

I agree that they can't HURT....but isn't "lower vacuum" a simple consequence of the increased overlap?

Meaning, if you install the cams perfectly, and they are perfectly degreed, (i.e. operating from a timing standpoint exactly how they were desgined to), wouldn't you still suffer a lower vacuum purely due to the built-in overlap?

Your post is making it sound like the OEM cam sprockets are the source of the decreased idle vacuum

army240

03-24-2010, 09:07 AM

My bad, I meant is when my cam was set on "0", the idle vacuum was lower than when it was degreed to True TDC, according to the BC degreeing diagram.

Frank

jspaeth

03-24-2010, 09:23 AM

I guess you are saying the vacuum can get even worse if the cams are not perfectly degreed?

That makes sense....but your original statement kinda made it sound otherwise.

Bigger, longer cams = less vacuum at idle bc of more overlap, it's just the way it is.

Sure you could change them to regain some of the idle vacuum back, but you would probably be doing more harm to the power output in other places.

army240

03-24-2010, 10:57 AM

midnight_rex

03-24-2010, 03:28 PM

i got JWT S4 cams with my t3/t4 (motor fully built from the top - down). what kind of street/response would i get out of it?

army240

03-24-2010, 03:59 PM

i got JWT S4 cams with my t3/t4 (motor fully built from the top - down). what kind of street/response would i get out of it?

I think we need more info... what kind of built? solid lifter? headwork? Stroker Kit? Manifold? etc...

midnight_rex

03-24-2010, 04:25 PM

I think we need more info... what kind of built? solid lifter? headwork? Stroker Kit? Manifold? etc...

CP 8.5:1 86.5mm pistons
eagle rods
balanced full assembly
ATI damper
oem nissan rod and main bearings

BC valve spring and retainers
BC 1mm+ exhaust/intake valves
suptech valve seals
JWT S4 cams
Apexi head gasket
all new rocker arms, shims, and guides
P2M RAS
ISIS intake manifold

turbonetics T3/T4 -.63 AR - Stage 3 wheel
SS top mount Log manifold
Haltech PS1000 EMS

dato

03-25-2010, 12:56 AM

motors are different but can be similiar results ???? honda motors respond well to aftermarket n/a cams for boosted setups, maybe for ka too?

army240

05-12-2010, 05:00 PM

Z U L8R

05-16-2010, 01:28 AM

not bad Frank, that's a pretty responsive powerband, car would definitely be fun to drive :D congrats brotha!

as far as my 2j goes, i got crower springs/retainers, the stock hg /w arp head studs, stock gte aristo bottom end....waiting to get some cams as the only cams i have are the usdm's....however they have a lot of surface rust and for my goal of 600+ which actually looks more like 700-800 i'm gonna need bigger cams...

so i'm deciding between the gsc s1's or the bc 264's....

i know i said i'd start with stock cams until i HAD to upgrade, but A. my power goal surpasses the stock cams' efficiency, and B. my stock cams are in pretty crappy shape.

i already got my sound performance quick spool valve, and instead of the gtx42/94r which is a 70.8mm turbo @ $2300+ , i'm rolling with the billy bad ass comp turbo vrp72ett, which is the borg warner s372 (72mm) which has the extended tip wheels with a triple ball bearing center section, for $1350 shipped /w a polished housing.

here's what the quick spool valve's look like, they also come with either a hobbs switch, or an electric boost solenoid your ems can control, available in t3, t4, and t6 flanges
http://i214.photobucket.com/albums/cc313/Z_U_L8R/012-1.jpg
http://i214.photobucket.com/albums/cc313/Z_U_L8R/013-1.jpg

i'm going with two bosche 044 fuel pumps, 1200cc injectors and e85, with aem series2 for engine management.

at 24-25psi it should EASILY queef out 700rwhp, but i may and knowing me probably will run 30psi.

i'm hoping and don't see why i shouldn't have 4,000 rpms worth of usable powerband.

instead of spending a jillion dollars and lots of time waiting on fab work to get the motor in my 71 240z, especially since i'm still waiting on the fab work for my little brother's project before mine can get movin....pics of his poop in progress

http://i214.photobucket.com/albums/cc313/Z_U_L8R/0142.jpg
http://i214.photobucket.com/albums/cc313/Z_U_L8R/0122.jpg

so unless i learn how to tig weld beautifully immediately lol, i'll be putting my 2j in my zenki s14 which is getting more goodies slowly but surely :)

anyways back on topic, i elaborated on the build so you could see the whole picture with my point being that

A. it's apples and oranges since this is a 3 liter motor that can spool a big ass turbo vs my previous posts in context referring to ~2.0 liter motors with huge cams

B. mine isn't a low 300hp build using big ass aggressive cam profiles (which in context was the purpose of this thread), it's more of a big ass hp build using pretty much the mildest aftermarket cams available.

C. i never said cam's didn't have their place in the scheme/purpose of builds, I mainly emphasized researching and knowing how your mod will effect your desired results and not just blindly doing the same mods as non turbo honda guys because the parts are available.

i'll keep you posted on my build if interested, i may just start a build thread once it's closer to completion...if there is a place for that on this forum, i still have a ways to go and some more doll-hairs to spend before she's done :)

anywho, here's a pic of my zenki daily this is going into once i'm done rounding up all my parts. in the meantime i'll keep driving her everyday cause cold AC kicks ass haha
http://i214.photobucket.com/albums/cc313/Z_U_L8R/001-2.jpg

still stock for the most part, just springs, brakes, and 35% tint, and lots of little tiny dings i can see cause it's a black car that are driving me nuts haha (i'm really convincing myself by justifying the need for aero mods, paint, and body work)

Dave

army240

05-16-2010, 08:23 AM

Haha, I see you still have some work to do!

I've got a question on the quick spool valve... how does that thing work?!? With one of the scroll close, the manifold pressure goes up, so turbo spools faster?!? when you achieve desired boost, the valve open, so everything flows nicely?!? Am I right or totally wrong?

What is the difference in spool time? Do you need to have a twin-scroll manifold absolutely?

Haha, I'm really curious :P

Frank

Z U L8R

05-16-2010, 09:04 PM

np, yeah this thing is freakin bad ass. it's like the simpleton version of a variable "vein" aka variable geometry turbo. basically the same effect

basically the quick spool valve + undivided manifold > legit twin scroll everything.

and how you understand it is correct.

basically it's like putting your thumb over your garden hose. it increases the velocity of the exhaust gas but not just that, that extra velocity is going to your exducer aka tips of your exhaust turbine and gets that sucker moving, then it opens up and allows flow to both sides of the exhaust housing without any restriction up top....

you use a non divided manifold, the qsv, and a twin scroll exhaust housing.

basically it takes your exhaust a/r whether it be .63 , .84, 1.00, or whatever, and momentarily cuts the size in half so then once your turbo wakes up it's wide open. therefore allowing you to run a bigger a/r than you'd normally run so you'd have more flow and thus power up top, yet gives you the benefits of having a smaller than you can even buy exhaust housing for response down low.

which is why in function it's like having a variable geometry exhaust housing since it gets smaller/bigger where it matters.

before i forked out $500 for this bad Larry i googled over and over again about this, cause it made sense to me how it worked and why it'd work but if it's kick ass, why the hell don't more people use it? answer: it's $500 hahah

so ya, i didn't find anyone anywhere that said it didn't work. the only 2 bad things i ever read about it were 1. people bitching about the price, 2. people that made their own, and had their's fail. but i never saw anywhere that anyone had a sound performance qsv fail.

looking at the thing man it really is a quality piece. if you wanna see real results of the thing in action check this out.
http://i52.photobucket.com/albums/g24/prelude760/Sound%20Performance/Evan%20turbo/DSC01241.jpg
http://i52.photobucket.com/albums/g24/prelude760/Sound%20Performance/Evan%20turbo/DSC01243.jpg
YouTube - Sound Performance Quick Spool Valve testing and results!!! (http://www.youtube.com/watch?v=I6ZCOTFET6s)
YouTube - Sound Performance Quick Spool Valve (http://www.youtube.com/watch?v=_KNLKVgg8po&feature=related)

^ those are youtube videos you can watch

i'm totally leary and skeptical, like "yeah you guys made the part of course you're gonna have a test that makes this thing look bad ass"

but beyond the sales-pitch it logically makes complete sense how it'd work

and if you look at that guy's powerband.. almost 100 more hp at 2800 rpm..~120 more hp at 3250, ~130 more hp at 3700.....

it's legit! don't worry, you can see how it works out on my car. i'll be the guinea pig, i already have mine.

:D

i would bet money that if you had an sr20det, with a full race or baller expensive twin scroll manifold and a gt28/71r .63 exhaust a/r and did a dyno pull at 18psi

then you put an undivided t3 log manifold, or even better apples and apples, an xspower top mount t3 undivided tubular manifold (since the full race is tubular too) with a quick spool valve and a gt30/76r .63 at 18 psi....

even after you spent 500 bucks on the quick spool valve, you'd have spent less money on your turbo set up, you'd have faster spool with the gt30r vs the gt28r and your WHOLE POWER BAND bottom to top power/torque would kick the 28's ASS!

therefore netting you, a better powerband, quicker response, more power/torque in general everywhere, and it'd cost you less.......

if i were doing a 60mm or bigger turbo on a ka i would do a qsv....ideally for my ka-t 510 once i start making progress on it again i will do a qsv + gt30r or something a lil bigger like a billet pte62 or a comparable comp turbo.

i haven't really gotten excited about an aftermarket product in a while..but man this thing totally pokes a fat finger in the eye of the saying "you can't have your cake and eat it too"

you can run a cheap ebay manifold, a bigger turbo and have better spool...or even just the same turbo you have now and some bigger cams for more power up top and it'll equalize your losses down low hahaha, i love it.

they should pay me for my endorsements :D! seriously though i'm psyched, i can't wait to try it out.

another encouraging thing for my build that i duly noted....even on that guy's dyno graph with the quick spool valve open the whole time.....it still is a responsive powerband.

it's a non ball bearing gt42 (70.8mm) with a .90 a/r turbo on a STOCK motor making ~450hp @ 4300rpm on up... even without the qsv working that's a fun 450hp car to drive....

then WITH the qsv...that thing is awesome!

the expression "if you can't beat em....join em" ....why i haven't had a 2j in any of my cars before this bewilders me... lol

for a month no one could answer my question "name me 2 motors that can make 1000+ hp on the stock bottom end for 2 years plus?"

answer 1 = 2jz-gte
answer 2 = ........................... took a while but someone said a viper motor...
even if they're correct and a stock bottom end viper motor can do it, which there is a guy here named joseph with a twin turbo 1300hp silver viper...however he's been through 3 motors because the crank snaps and the harmonic balancer flies off the motor lol, and now he's fully built... so i'm still talking stock motor....

so even if my buddy who said a viper motor is correct.....2j motorset = $1800 + 1000-1500 for trans/clutch/bellhousing...so lets say 3300 for a 5 speed 2j motor set that comes with forged pistons from the factory, capable of lets be conservative and say 600hp all day every day won't bat an eye..... how much is a viper motor?? i rest my case...

how many stock bottom end rb26's do you see/hear about with bolt on's reliably cranking out 600hp?

and even if you did get passed the notorious weak rb ring land issue...it's still a 2.6L vs 3.0L. lol just sayin

don't get me wrong...i'm a devout nissan guy....we all know and most will agree though that a 2j > rb26....i hope...but no longer can i keep a blind eye to how much better an inline 6 motor it is to nissan's I6... i can only hang on to my pride for so long until i must admit....although it's a heavy ass frickin motor.....it's King....and non-interference too :P

my .02, justification/blog/rant

Dave

ps this is my thread and i do what i want in my thread hahahha, to stay back on topic, you can run big ass cams if you have a quick spool valve.......maybe lol.