SR20det Rocker Arms keep popping - Page 2 - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

SoCalDrifter · 04-14-2014, 08:52 PM

and now tomei's back ordered till the end of may on cams and frsport had the one i need and i called back and it was already sold....what are the chances... so now im on the search otherwise a long shitty down time again

*TheRealSy90* · 04-14-2014, 10:38 PM

Are you revving higher than 7500rpm? If not then the turbo isn't going to have any effect on the hydrolic lifter's performance. That is really just an rpm issue, and i've only heard of the aem rev limiter being the one that tends to throw rocker arms due to the gain/how fast it hits the limiter. And like I said, with dual guides the rocker cannot throw, so the solid lifter has no benefit. Might as well put rocker arm stoppers on it as well.

SoCalDrifter · 04-16-2014, 02:35 AM

Quote:

Originally Posted by TheRealSy90

Are you revving higher than 7500rpm? If not then the turbo isn't going to have any effect on the hydrolic lifter's performance. That is really just an rpm issue, and i've only heard of the aem rev limiter being the one that tends to throw rocker arms due to the gain/how fast it hits the limiter. And like I said, with dual guides the rocker cannot throw, so the solid lifter has no benefit. Might as well put rocker arm stoppers on it as well.

when i was blowing up rockers it would only occur when i hit or was bouncing off the rev limiter to long/much so at like 7400rpm and i had a RAS even then wasnt doing the trick so thats why i got solid lifters and cams and dual guide shims so i can turn the rev limiter up a good amount

SoCalDrifter · 04-23-2014, 11:49 AM

so got the car tuned put down about 450-470whp on the dyno at 8500rpms took it out to the track yesterday for some testing everything was running perfect until my stupid clutch fan broke and messed up my water pump and ended the day gunna go out again on thursday so far so good with the setup.....finally

Drakkar · 04-23-2014, 12:11 PM

solid lifters are good for high rpm. The hydraulic lifters are noisy when they get old. Street vs race take your pick. Have you already installed your guides? what size did you end up going with?

SoCalDrifter · 04-23-2014, 02:10 PM

Quote:

Originally Posted by Drakkar

solid lifters are good for high rpm. The hydraulic lifters are noisy when they get old. Street vs race take your pick. Have you already installed your guides? what size did you end up going with?

ya installed the dual guides along with tomei solid 260 intake cam and 270 exhaust cam just because thats all i could get my hands on since tomei is back ordered about a month on cams but pretty happy with the 260/270 alittle more pick up

*TheRealSy90* · 04-23-2014, 06:49 PM

Quote:

Originally Posted by Drakkar

solid lifters are good for high rpm. The hydraulic lifters are noisy when they get old. Street vs race take your pick. Have you already installed your guides? what size did you end up going with?

oem Guide shims are all the same thickness.

SoCalDrifter · 04-23-2014, 11:08 PM

Quote:

Originally Posted by Drakkar

solid lifters are good for high rpm. The hydraulic lifters are noisy when they get old. Street vs race take your pick. Have you already installed your guides? what size did you end up going with?

o ya if your talking about guide shims i just used stock

AJZax · 04-24-2014, 04:20 PM

What springs did you go with?

All R.A.S. will do the same thing, don't waste time with them. Doesn't matter the brand.

I took mine and sat on the rev limiter at 8k for 4 minutes, almost straight, just TONS of rev limiter. I'm running tomei dual springs and ti retainers. OEM hydro lifters, factory shims and guides, on oversized valves (light ferrea and BC ones [don't ask why they're mismatched, I don't want to talk about it hahaha]) and I'm running 270 tomei pro cams. 12.5mm lift? (could be wrong it's from memory)

What cams are you running with what springs?
Every spring has a resonance, and at certain RPMs this can resonate "just right" to prevent the spring from functioning normally, there's also spring bind. This is where dual valve springs are great because it staggers the "efficiency" ranges, which makes it so there's always an effective spring.
Be careful with too heavy of springs also, as at idle with too stiff of spring you can start burning cams with an idle set too low.

*TheRealSy90* · 04-24-2014, 06:11 PM

Camp ramp has a lot to do with it as well. JWT cams can run rev limiter all day on a stock sr with no problem, BC not so much say goodbye to rocker arms without dual guides or upgrades lol.

SoCalDrifter · 04-25-2014, 12:25 PM

Quote:

Originally Posted by AJZax

What springs did you go with?

All R.A.S. will do the same thing, don't waste time with them. Doesn't matter the brand.

I took mine and sat on the rev limiter at 8k for 4 minutes, almost straight, just TONS of rev limiter. I'm running tomei dual springs and ti retainers. OEM hydro lifters, factory shims and guides, on oversized valves (light ferrea and BC ones [don't ask why they're mismatched, I don't want to talk about it hahaha]) and I'm running 270 tomei pro cams. 12.5mm lift? (could be wrong it's from memory)

What cams are you running with what springs?
Every spring has a resonance, and at certain RPMs this can resonate "just right" to prevent the spring from functioning normally, there's also spring bind. This is where dual valve springs are great because it staggers the "efficiency" ranges, which makes it so there's always an effective spring.
Be careful with too heavy of springs also, as at idle with too stiff of spring you can start burning cams with an idle set too low.

I have BC TI dual springs and retainers with Tomei solid lifters and tomei solid 270 ex cam and 260 intake cam with 12.5mm lift.....took it out to the track last night running like a beast was at like 7-8 in 2nd gear all night a 3rd gear 5-6k (small track only can get it in 3rd for a few seconds)

GroundPerformance · 04-25-2014, 01:49 PM

Will all that money on the headwork. A stock VVL head swap would have been a better move.

SoCalDrifter · 04-25-2014, 10:42 PM

Quote:

Originally Posted by GroundPerformance

Will all that money on the headwork. A stock VVL head swap would have been a better move.

ya i thought that half way threw but it was to late

*TheRealSy90* · 03-24-2015, 01:26 PM

So how has it been working out for you? Next move for me is installing oem hydo lifters from a roller-rocker sr20de. They have larger oil ports and perform like solid lifters at high rpm, but are still quiet at low rpm and require no maintenance or periodic measurements like solid lifter kits.

Kingtal0n · 03-24-2015, 02:15 PM

I am surprised nobody mentioned the fuel cut setting in the AEM vs. spark cut.

Isn't the ignition cut notorious for causing rocker problems?

First thing i would do is make your rev limiter fuel only, and soften it. Off at 7200 on at 6970 something like that.

*TheRealSy90* · 03-24-2015, 02:17 PM

Yeah that's seemed to be the consensus regarding AEM limiter issues. I know the oem ecu uses a combination fuel/ignition cut that is fairly kind to rocker arms.

I always thought that a strictly fuel cut rev limiter would cause a lean issue since you are still on the throttle, and possible engine damage?

Kingtal0n · 03-24-2015, 02:30 PM

Quote:

Originally Posted by TheRealSy90

Yeah that's seemed to be the consensus regarding AEM limiter issues. I know the oem ecu uses a combination fuel/ignition cut that is fairly kind to rocker arms.

I always thought that a strictly fuel cut rev limiter would cause a lean issue since you are still on the throttle, and possible engine damage?

The ecu is either injecting fuel, or not. There is never a situation where it will only inject "some" fuel. The ecu makes a decision call, before the intake valve even opens (usually) whether to inject or not. The AEM instruction manual specifically says injector phasing should be timed such that the end of the injector pulse is before the intake valve opens. It also says "never inject fuel into an open valve".

A lean condition can only happen if you have a not quite enough fuel, as if your fuel pressure drops ~10psi and you lose 12% of your injector capacity. If it goes much leaner than that, it will misfire. There is not much room for error, not to mention that a lean condition in an sr20det, from experience I am talking now, does not by itself cause immediate damage if the engine is tuned properly. the lean condition might take a few WOT passes (yes complete passes on a dyno for instance) before the heat builds up to the point where it ruins your piston rings. A single, complete, leaning out to (17:1),WOT pass, on a built sr20det with forgies and proper ignition timing, 20psi of boost on pump gas 93 octane 420BHP, will not hurt anything. Yes it the EGT will sky rocket and your warning light will go off to cool down the engine, but it will live. So Even if it were possible to be "slightly lean sometimes because of a rev-limiter related failure" even that should not have any lasting consequences. OEM engines are different though, the OEM pistons/rings do not tolerate these 17:1 WOT passes, so don't try that.

Spark cuts on the other hand lend all sorts of dangerous situations. You remove the spark but not the fuel- where does the fuel go? Some of it stays behind, the rest dumps into the exhaust system where it probably explodes as it passes the turbine. Good for spooling that turbine, bad for the engine, for many reasons that I am unfamiliar with. I could guess that it isn't good for the cylinder walls and rings, and I could guess that the residual fuel will interact and alter your next cylinder event, in perhaps unpredictable ways (the fuel is no longer atomized and suspended, ready for a proper burn) but these are just guesses. I am sure you could google "ignition cut engine failures" or "2-step ignition engine failures" or similar to get a few pictures of engines that fell apart while sitting on a spark cut.

*TheRealSy90* · 03-24-2015, 02:40 PM

Yeah I didn't mean that it injects "some" fuel, but that it alternates between fuel cut and ignition cut while hitting the rev limiter. Well that is what Martin at R.S.Enthalpy told me about the factory ecu limiter. That it is neither strictly fuel nor ignition.

Kingtal0n · 03-24-2015, 03:13 PM

Quote:

Originally Posted by TheRealSy90

Yeah I didn't mean that it injects "some" fuel, but that it alternates between fuel cut and ignition cut while hitting the rev limiter. Well that is what Martin at R.S.Enthalpy told me about the factory ecu limiter. That it is neither strictly fuel nor ignition.

I did some quick searching around... for similar topics

http://www.sr20-forum.com/tunercode/...iscussion.html

http://www.sr20-forum.com/tuning/143...html#post19535

http://www.sr20-forum.com/tuning/439...-limiters.html

Quote:

The puddle I referred to is called the "Tau"? puddle, and is referenced in a lot of tuning books I've read. It has been very difficult to actually piece all of this information together for me. It seems like every other person I talk to has conflicting statements about whether or not it would cause detonation. Some said there is not enough fuel to actually combust. I've talked to several tuners about this puddle, and a lot of them looked at me funny, scratching their heads.

I even brought it up to JWT and their tech said they have never heard of this. The factory Nissan computer cuts injectors one at a time for the rev limit.

Quote:

I had my ignition cut set at 7400rpm with the JWT limiter at 7500rpm and I would still "bounce" the limiter. I set the MSD to 7300rpm and it stops right there! Also, the torque curve suggests that the MSD pulls timing by a few degrees on the top just before the actual cut. It makes it very very smooth. Look at my 3rd gear burnout video and you can see how smooth it is.

Quote:

"Apparently spark cut comes from the days of carbs before fuel could be cut. Most people recommend and prefer a fuel cut. I'm not 100% convinced it's completely safe although it's going to be better than a strict spark cut.

I still think cutting both at the same time is best or if you have to then cut fuel first immediately followed by spark. There must be a reason why it isn't traditionally done that way since it seems so simple, easy, and effective. I feel like I'm missing something. "

Quote:

"The QR25 rev limiter cuts fuel.

No late model OEM car cuts spark, it would be very
damaging to the cat."

Quote:

"Here is how the current rev limiter works. There is a cut within the control range (smooth cutting), then there is a hard cut following that. The control range cut is all based around a percentage cut. The percentage can be considered a percentage of power reduction. The control range is below the RPM limit set in the table. In the advanced settings you can adjust the percentage cut at the start and end of the control range. The percentage cut at any point within the control range is interpolated from the start and end cut. The percentage is the number of missed firing events over a fixed number of firing events. Say for example the fixed number of firing events is 32 and the percentage cut is calculated to be 25% at a specific RPM. This means that over the 32 events, 8 of them will be missed, this spread out across the 32 events means that every 4th event will be missed. Hence reducing the power output from the motor by 25%. This same principle works for any given percentage. The hard cut is obviously all cylinders completely cut until the RPM falls below the hard cut activation. Adjusting the start and end cuts controls how aggressive the limit comes on. You will notice that there is a TPLow and TP100%, this if for correcting the start cut based engine load. (You don't need such an aggressive cut at lighter loads). This system of cutting allows you to have a limit that holds a perfectly stable RPM. Having a perfectly stable RPM limit allows for much more repeatable launches when using launch control. The choice between fuel and ignition cut is based on the application, there are pros and cons to both. Launch control typically calls for ignition cutting as it allows fuel to burn in the exhaust, banging and helping the turbo to spool up. With ignition cutting the chance of detonation is very small. The downside to ignition cutting is the banging in the exhaust can force the exhaust valves open, this can take load of shims (they may fall out) or it could allow a hydraulic lifter to pump up meaning the exhaust valve won't close fully. Heavy duty valve springs protects against this problem. The final problem with ignition cut is that it destroys catalytic converters, hence stopping factory from ever cutting the ignition. Fuel cutting eliminates the banging exhaust and keeps the exhaust valves happy, but can punish the bottom end instead. Detonation is common when fuel cutting (explained by Kieran's last post). Even factory cars detonate on the fuel limiter. Even though detonation is not ideal, engines can withstand it, as long as its not too extreme. When Nissan designed its factory rev limiter they probably weren't thinking that people would drive down the road wide open throttle on the rev limiter, although in saying that the cars were sold with a warranty. Rev limiting is never going to be good for the engine, but if its necessary do it and you engine will probably be fine. I know from experience that stock sr20 heads don't like ignition cuts as the hydraulic lifters pump up and hold the valves open, causing the motor to run on less that 4 cylinders for a few seconds. There is rev limit ignition trim which is ideal for fuel cut as it reduces the chance of detonation. If you want your fuel cut to be more aggressive like the stock, turn advanced mode on, change the control range from 200 down to 100, and you will start to see results. The next thing to do is increase the start cut values. Hope this points you in the right direction. "

From what I gather, our sr20det ecu is fuel cut only, and it does so by eliminating 1 cylinder at a time up to the "hard cut" limit. So is the power FC afaik.

AEM has the option to cut both, and the factory configuration file is set for spark first (like a "race" car with no cat). Which is why I posted to begin with- that initial spark cut was probably causing the symptoms they described in several threads, causing rocker failure.

Kingtal0n · 03-24-2015, 03:29 PM

more info

high performance hyabusa,

fuel cut first, "soft" followed by a hard full cut of simultaneously fuel/spark
http://www.hayabusa.org/forum/nitrou...uel-spark.html

http://honda-tech.com/drag-racing-36...miter-1981086/
"Dont cut fuel while using nitrous..."

Quote:

Originally Posted by tony1
It cuts the injector completely for a cycle, it doesn't cut the injector in the middle of a cycle, it does not create a lean condition because there is no fuel in the cylinder when it happens. OEM's wouldn't do it if it could damage an engine...

Your bearings would have spun regardless of the type of cut you used.

Quote:

amen brother.i have been using fuel cut on mine for about 5 years now with no problems.mine bangs the rev limiter many,many times each pass.

Traction control
http://www.racelogic.co.uk/index.php...l#how-it-works

Quote:

Cutting a single injector pulse:

The idea of cutting fuel to an engine sets alarm bells ringing in engine builders, as they all know that running a lean combustion mode will elevate in-cylinder temperatures very rapidly. The denser the air/fuel charge, the more heat the lean burn can generate. Therefore it is vital that a fuel cut system will not cause a lean burn.

RACELOGIC Traction Control prevents lean burn by removing 100% of the pulsed fuel delivery – essentially the affected cylinder takes a gulp of fresh air; the in-cylinder temperature remains virtually unaffected.

Prolonged fuel cut on one particular cylinder would cause scavenging of the petrol lining the inlet tracts, and when the next full fuel pulse arrived, it would be partially reduced in quantity by the re-wetting of these tracts. RACELOGIC Traction Control rotates cylinder cutting to prevent this situation from occurring."

*TheRealSy90* · 03-24-2015, 03:53 PM

Lots of really great information in those posts, that is probably way over the head of the average 240sx owner haha. The posts about the TAO puddle are very intriguing.

Quote:

Originally Posted by Kingtal0n

I know from experience that stock sr20 heads don't like ignition cuts as the hydraulic lifters pump up and hold the valves open, causing the motor to run on less that 4 cylinders for a few seconds.

Now this really caught my eye. I have noticed a few times after going to the Entlaphy ROM tune, that there have been a couple instances where I hit the rev limiter, and then it seemed that the engine would have a brief missfire afterwards. Maybe the rom tune is now using a spark cut to an extent, causing this "lifter pump up" and valves to not close all the way briefly. I mean even a split second is still hundreds of rpm when compared to how high we are revving. This is the first time i've read about this issue, as i'm sure it's coming from someone with tons more experience. Those fwd forums really have the best tech guys haha.

So unfortunately there are pro's and con's of both spark and fuel limiting. And figuring out the best mixture of the two seems to be the way to go. I'm curious if anybody has managed to configue the rev limiter to hold a perfectly steady rpm, as they do with the lower rpm "launch control", which should be the least jarring to the valvetrain and engine as well.

*TheRealSy90* · 01-29-2016, 02:55 AM

Quote:

Originally Posted by Kingtal0n

I am surprised nobody mentioned the fuel cut setting in the AEM vs. spark cut.

Isn't the ignition cut notorious for causing rocker problems?

First thing i would do is make your rev limiter fuel only, and soften it. Off at 7200 on at 6970 something like that.

Bumping this. Is it possible to set an AEM rev limiter to hold a "constant" rpm, so that the rpms aren't really bouncing up and down?

So did we reach a consensus that fuel cut is the way to go, so on an AEM would I want to disable the spark cut completely and strictly rely on the fuel cut settings? Not sure if that's even possible haven't looked in my tuner software in a while.

Kingtal0n · 01-29-2016, 05:01 PM

Yes fuel cut, set it softly well before your actual redline. On an OEM bottom end, the OEM redline being around 7200rpm, I set my rev limiter to around 6800 for street cars. You don't want to spin much higher than that on a tight OEM bearing. It's just a safety precaution I take when people say they want to drive for 100k+ miles, this is one of the little things you can do to get the engine to last 10+ years, is to be generous with the RPM limiting (its just a "fun" car, no competition, so minimize risk) Its different if you have an aftermarket tricoat bearing with a .0022" clearance, then you can go to the sky and use a thicker oil. I've taken those to 8200rpm on the OEM lifters, no trouble, but I wouldn't do it repeatedly.

If you set the spark limiter much higher than you will ever go, you wont ever touch it. Newer versions of AEM have different models for fuel cut. The latest versions cut individual cylinders one at a time until the threshold for a softer cut. I am not sure when they started doing that though.

Croustibat · 01-30-2016, 05:56 PM

Quote:

Originally Posted by TheRealSy90

Bumping this. Is it possible to set an AEM rev limiter to hold a "constant" rpm, so that the rpms aren't really bouncing up and down?

The way to do this is to retard timing a lot. Be aware this is going to produce a lot of heat.

*TheRealSy90* · 01-31-2016, 09:20 AM

Kind of weird how when i was on the stock ecu years ago it revved to 7500 sometimes 7550 if I flat shifted.

Sent from my iPhone using Tapatalk

04-24-2014, 04:20 PM	#39
AJZax Leaky Injector Join Date: Feb 2012 Location: WA state Posts: 123 Trader Rating: (3) Feedback Score: 3 reviews	What springs did you go with? All R.A.S. will do the same thing, don't waste time with them. Doesn't matter the brand. I took mine and sat on the rev limiter at 8k for 4 minutes, almost straight, just TONS of rev limiter. I'm running tomei dual springs and ti retainers. OEM hydro lifters, factory shims and guides, on oversized valves (light ferrea and BC ones [don't ask why they're mismatched, I don't want to talk about it hahaha]) and I'm running 270 tomei pro cams. 12.5mm lift? (could be wrong it's from memory) What cams are you running with what springs? Every spring has a resonance, and at certain RPMs this can resonate "just right" to prevent the spring from functioning normally, there's also spring bind. This is where dual valve springs are great because it staggers the "efficiency" ranges, which makes it so there's always an effective spring. Be careful with too heavy of springs also, as at idle with too stiff of spring you can start burning cams with an idle set too low. __________________ www.ajdrift.com Mansfield, A - 145

04-25-2014, 01:49 PM	#42
GroundPerformance Zilvia FREAK! Join Date: Oct 2008 Location: Socal Posts: 1,477 Trader Rating: (44) Feedback Score: 44 reviews	Will all that money on the headwork. A stock VVL head swap would have been a better move. __________________ SoCal KA24DET/KA24ET Owners << Join the FB Group >>

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04-14-2014, 08:52 PM	#31
SoCalDrifter Nissanaholic! Join Date: Jan 2010 Location: Thousand Oaks-818 Posts: 1,990 Trader Rating: (10) Feedback Score: 10 reviews	and now tomei's back ordered till the end of may on cams and frsport had the one i need and i called back and it was already sold....what are the chances... so now im on the search otherwise a long shitty down time again

04-23-2014, 11:49 AM	#34
SoCalDrifter Nissanaholic! Join Date: Jan 2010 Location: Thousand Oaks-818 Posts: 1,990 Trader Rating: (10) Feedback Score: 10 reviews	so got the car tuned put down about 450-470whp on the dyno at 8500rpms took it out to the track yesterday for some testing everything was running perfect until my stupid clutch fan broke and messed up my water pump and ended the day gunna go out again on thursday so far so good with the setup.....finally

04-23-2014, 12:11 PM	#35
Drakkar Join Date: Oct 2013 Location: Nh Age: 33 Posts: 18 Trader Rating: (0) Feedback Score: 0 reviews	solid lifters are good for high rpm. The hydraulic lifters are noisy when they get old. Street vs race take your pick. Have you already installed your guides? what size did you end up going with?

03-24-2015, 02:15 PM	#45
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	I am surprised nobody mentioned the fuel cut setting in the AEM vs. spark cut. Isn't the ignition cut notorious for causing rocker problems? First thing i would do is make your rev limiter fuel only, and soften it. Off at 7200 on at 6970 something like that.

01-29-2016, 05:01 PM	#53
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	Yes fuel cut, set it softly well before your actual redline. On an OEM bottom end, the OEM redline being around 7200rpm, I set my rev limiter to around 6800 for street cars. You don't want to spin much higher than that on a tight OEM bearing. It's just a safety precaution I take when people say they want to drive for 100k+ miles, this is one of the little things you can do to get the engine to last 10+ years, is to be generous with the RPM limiting (its just a "fun" car, no competition, so minimize risk) Its different if you have an aftermarket tricoat bearing with a .0022" clearance, then you can go to the sky and use a thicker oil. I've taken those to 8200rpm on the OEM lifters, no trouble, but I wouldn't do it repeatedly. If you set the spark limiter much higher than you will ever go, you wont ever touch it. Newer versions of AEM have different models for fuel cut. The latest versions cut individual cylinders one at a time until the threshold for a softer cut. I am not sure when they started doing that though.