KA24DE N/A Dyno

[240sxaddict]

Dyno'd a friends S13 KA before we throw on a turbo. Stock low mileage motor, 3" exhaust.

It was 89ºF with 29%humidity on a Dynojet.

http://i8.photobucket.com/albums/a17/nodorifto/RODSKAT.jpg

Pretty damn good I'd say. AND NO LOSS OF TORQUE!!! Haha, still fighting that backpressure myth.

[racepar1]

The whole "backpressure theory" is just plain bullshit. Looks like a pretty strong motor man!

[240sxaddict]

The whole "backpressure theory" is just plain bullshit. Looks like a pretty strong motor man!

You'd be suprised how many people still hold dear to that myth, even with all the people I've proven wrong. Now I have first-hand proof :bigok:

[BlitzRPS13]

That's a strong motor.

[[w]hite[r]abbit[x]]

Wow it has a big jump in power right before redline. I'm thinkin' about getting a 3 inch BRM exhaust system with high flow cat.

[mewantkouki]

^ Resonated test pipe ftw! High flow cats are a waste of money, unless you have to pass emissions...

[SoguRacing]

backpressure is not a myth. do some research

[UNISA JECS]

Page 13 is what you need to know;

http://books.google.com/books?id=2YAeTmG60OMC&pg=PA13&dq=exhaust+size+mike+kojima&sig=cW9QaDWGRfEGjuaVTYlNxqW2ZJo

[blu808]

wow. thats a strong Ka. i remember scooters hi comp itb ka only made like 155 whp

[timster]

Damn what a lack of backpressure though. If you had like.. a 1 inch pipe you'd probably have 200 at the wheels. (:

/Sarcasm

Strong engine though :tup:.

[UNISA JECS]

Also looks like you got knock issues by the way the horsepower shoots up after 5200rpm, because at 5200rpm the ECU no longer has control over ignition timing, it could be real knock issues or false knock issues, the later would be because of wiring harness issues.

[racepar1]

backpressure is not a myth. do some research

Follow the link below and then try to feed me the whole backpressure bullshit again. Plenty of v8's need dual 3" exhausts. The displacement of the KA is about 1/2 of the typical v-8, so a single 3"exhaust will be perfect for a KA.

Page 13 is what you need to know;

http://books.google.com/books?id=2YAeTmG60OMC&pg=PA13&dq=exhaust+size+mike+kojima&sig=cW9QaDWGRfEGjuaVTYlNxqW2ZJo

[90KAcoupe]

idc which is better but everbody saying its a myth is completely wrong.. its more of a tuneable thing... look at most race cars. alot of them either have tunable headers or tuneable mufflers.

[EDacIouSX]

yada yada yada. so when are we seeign the turbo dyno sheet?

[ryguy]

Sure you have a ton of high rpm torque with the 3 inch exhaust, but wouldn't the low rpm torque be slightly higher with a 2.5"? I mean, there is a trade off.

[amaank]

Dynojets read way way high... and consequently keep people happy. What were the uncorrected numbers?

And if you want a more realistic 'heartbreaking' reading next time, try a dyno dynamics. This car would probably put down about 110-115whp on a more accurate dyno.

[McRussellPants]

Dynojets read way way high... and consequently keep people happy. What were the uncorrected numbers?

And if you want a more realistic 'heartbreaking' reading next time, try a dyno dynamics. This car would probably put down about 110-115whp on a more accurate dyno.


or 125. or 160 or 90.

but you know, as long as the fuckup setting the load is "more accurate" I'd say you're correct about it being more accurate.

in before you link to this to the guy that you parroted that from and he has something intelligent to say instead of random internet flavor of the month.

[240sxaddict]

The backpressure myth we're talking about is how everyone proclaims there is a noticeable loss in torque when a 3" exhaust is installed on a N/A KA24. While it is true you do need a small amount of backpressure to create the velocity necessary to create good flow, 3" exhaust on a KA has shown nothing but improvements in power. We're not saying you dont need any backpressure, we're saying you don't need as much as people think.

As for the dynojet reading high, anytime anyone posts dyno numbers there will always be that comment. This was more for 3" debate on other forums. I threw it up on here out of boredom, I rarely post on this site but have been lurking this site more as time goes by. And the uncorrected numbers were slightly higher...

And scooters KA made 180whp iirc. The 155whp was when it wasnt getting enough fuel I think.

[racepar1]

Ok people, backpressure is BAD! BackPRESSURE slows down the flow of exhaust gasses. PRESSURE is caused by a restriction, a RESTRICTION slows the flow. VELOCITY is important. If you put a small amount of gasses through a small tube it will move very quickly. If you put that same amount of gasses through a large tube the flow will slow down. A high speed flow through the exhaust is good because it actively scavenges the exhaust gasses out of the cylinders, it acts almost like a vacuum. Backpressure and exhaust velocity are TOTALLY different things, don't get them mixed up. A 3" exhaust is not big enough to severely hurt velocity with the pretty large 2.4 litre displacement of the KA. Think about it, how many 4.6L mustangs run DUAL 3" ehxausts? A KA is .2L more than 1/2 a 4.6 mustang motor so why would a SINGLE 3" exhaust be a problem. You also have to know that this supposed drop in torque would be so minimal that it would go un-noticed. If you ENGINEERED the PERFECT exhaust system for your car you would probably gain 5hp or lb/ft or less over the run of the mill, off the shelf system. Exhaust tuning nets MINIMAL gains when you are talking about comparing an off the shelf high flow set-up to a perfectly engineered one-off racing set-up.

[McRussellPants]

an exhaust with zero backpressure up top will stagnate down low, making for bad tip in and response and steeze.


I've been told you can feel it with 3in on a KA, but i don't care because its an NA KA and its gonna suck shit with a 2.5 or 3in so whatever.

[racepar1]

an exhaust with zero backpressure up top will stagnate down low, making for bad tip in and response and steeze.


I've been told you can feel it with 3in on a KA, but i don't care because its an NA KA and its gonna suck shit with a 2.5 or 3in so whatever.

Please clarify the above statement. I understand response, but tip in and steeze? WTF does that mean?

[BigVinnie]

You'd be suprised how many people still hold dear to that myth, even with all the people I've proven wrong. Now I have first-hand proof :bigok:

The only truth to back pressure is smog emissions. You need back pressure to feed the egr system other than that, it doesn't mean shit.
The other debate is that an egr assembly is to help shrink pulse width of injection by allowing exhaust gas to bypass the manifold, hence helping gas mileage.
I find this to be false, since every modified exhaust I have installed has lowered back pressure, lowered exhaust gas through the manifold, and increased my gas mileage.
The real truth to it is that an engine has less resistance to back pressure, therefore more energy is focused to the drive train which is added power regardless. Back pressure is a form of resistance and it consumes more energy like a parasite even when the pulse width of the injectors is shrunken from exhaust gasses that bypass the intake manifold.
If you look at old mid 60's toyota and Nissan engines that didn't use catalytic and egr systems most of those engines could make relatively 35~40MPG, and were great performance engines for there era.
So technically the larger the exhaust the more TORQUE and HorsePower the engine can make since pulse width isn't shrunk and all the power can be delivered to the drive train. It's just like funny car engines, or highly modified track engines that use what is header out, since the pulses are no longer needed after it has been reached a few inches after the collector.

[Forge_55b]

I know everyone has their views on backpressure etc, but does anyone have any actual data? until someone can actually show that, you are just basing it on "your" theories without any actual data

and in regards to KA's they like to breathe and that is common knowledge.......maybe not a 5" open pipe but 3" seems to work better then 2.5" from dyno charts that people have shown that compared the two....

[racepar1]

It's really simple. Pressure is caused by a restriction of some sort. A restriction means that the engine has to push the exhaust gasses out of the cylinders, and it takes energy to push the exhaust out. If you eliminate the restrictions it takes very little energy to push those gasses out, which means more energy going towards turning the wheels. If you get the piping diameter just right the exhaust flow out the pipe essentially sucks the exhaust out of the cylinders, which gives you just a tiny bit more total power. Like I said before, it is not the pressure that is any concern it is the velocity of the exhaust flow. You are asking for numbers, but the differences would be pretty un-noticeable. Just to show you how little of a difference fine-tuning the exhaust Will make I will tell you this story. My dad had a new set of headers made for his atlantic car and the guy who built them sucked ass. The common theory is that equal length headers make a big difference in performance. Well the headers that were made had a foot of difference between the shortest and longest pipe. So we took both sets of headers to the engine dyno. There was no noticeable difference in power, torque, or the curves between the two headers. I'm sure if you analysed the hell out of the charts you could find places where the equal length headers had a slight advantage, but not enough to lose sleep over. Exhaust tuning does not net as noticeable of gains as most people would think.

[projectRDM]

The only truth to back pressure is smog emissions. You need back pressure to feed the egr system other than that, it doesn't mean shit.
The other debate is that an egr assembly is to help shrink pulse width of injection by allowing exhaust gas to bypass the manifold, hence helping gas mileage.
I find this to be false, since every modified exhaust I have installed has lowered back pressure, lowered exhaust gas through the manifold, and increased my gas mileage.
The real truth to it is that an engine has less resistance to back pressure, therefore more energy is focused to the drive train which is added power regardless. Back pressure is a form of resistance and it consumes more energy like a parasite even when the pulse width of the injectors is shrunken from exhaust gasses that bypass the intake manifold.
If you look at old mid 60's toyota and Nissan engines that didn't use catalytic and egr systems most of those engines could make relatively 35~40MPG, and were great performance engines for there era.
So technically the larger the exhaust the more TORQUE and HorsePower the engine can make since pulse width isn't shrunk and all the power can be delivered to the drive train. It's just like funny car engines, or highly modified track engines that use what is header out, since the pulses are no longer needed after it has been reached a few inches after the collector.


Bingo. Someone send this guy a beer.

[BigVinnie]

If you get the piping diameter just right the exhaust flow out the pipe essentially sucks the exhaust out of the cylinders, which gives you just a tiny bit more total power. Like I said before, it is not the pressure that is any concern it is the velocity of the exhaust flow.

This is a characteristic of pulse scavaging. If the pipe is to large you can decrease the velocity, you can also disrupt the pulse that runs out the exhaust pipe since it isn't the typical header out situation the dynamic and principle changes a bit because it is a streetable exhaust not a header out type exhaust.
This of coarse has more to do with (engine size), injector pulse width, and of course the major factor of ignition timing.
I simply look at it like this......
I have a 60mm Throttle body on my KA24de, so what goes in needs to come out at the same rate of speed. During valve overlap it creates a velocity charge from the intake to the exhaust so as long as your pipe is that of the equivalent of the throttle body there typically shouldn't be any huge issues with back pressure accept of course if your engine uses a catylitic converter. Most dyno's that I have seen on NA KA's comparing 2.5" to 3", I really haven't seen any drastic results that should make me go out and buy a 3" over my 2.5".
Do we know pulse scavaging exist's? Yes we do because the basic fundamental is that without a runner type to maintain the internal suction of velocity which helps to generate power, the engine will do the opposite and run very sluggish.
I saw an article a few years pback on a sentra se-r performance build, and when they dynoed the car with no header the engine lost 20ft/LB's of torque, as well as 20HP. But this principle deals with exhaust pulse scavaging, not back pressure at all.

[UNISA JECS]

Everyone needs to read page 13 of the link I posted above, I remember to back in my http://www.se-r.net/ days, I believe Mike Kojima did a write up on this to and the suck, squish, bang, blow write up as well.

[rod0921]

Also looks like you got knock issues by the way the horsepower shoots up after 5200rpm, because at 5200rpm the ECU no longer has control over ignition timing, it could be real knock issues or false knock issues, the later would be because of wiring harness issues.

this is actually my car, 240sxaddict addressed this on another board...theres actually no knock sensor in there right now which explains the "vtec" like jump over 5200, he just dyno'd it as is to get a rough idea for "before" numbers.