I would like this cleared up for me. I read in this forum under some exhaust search, that on a KA24DE NA, that a 3" exhaust piping is good up to 16rwhp and doesnt loose torque?? please someone tell me that this is rediculously wrong! My other question is what is the right size to upgrade to from stock, is it 2.25"?

many many many threads have taken this topic... most of them, with proof (dino(sp?) charts) have shown that there are gains in top end, and very very minimal losses in lower end torque.... it will however be pretty loud @ WOT as for ?? #2... it is up to you what size to go with... if you are keeping your car NA then 2.25 or 2.5 will sufice, if you have a thought of going turbo i would go 3, that way if you do go turbo, you wont have to get a new exhaust sys. but it will be louder than the 2.5 when in a NA platform

you'll lose too much back pressure... back pressure isnt good, but some motors are tuned to run on some, including all stock motors! you WILL NOT see huge gains on a stock motor, just sluggish off the line not to mention rediculously loud. A good NA (naturally aspirated) size is 2.25-2.5"

-Dan

"back pressure" is a myth.

Some exhausts work on scavenging effect...Its like syphoning.. once you get some pressure on a fluid.. it creats a vacuum and draws more out as well with negative pressure.

3inch is dyno proven on NA to still add horse power and to loose very little if any torque.

Backpressure is a myth. The truth of the matter is you want 0 backpressure with as high of a velocity as you can. Thats why most people suggest a 2.5" piping, because since it is smaller, it will flow your exhaust out of your motor faster because of its smaller diamater. Its all about velocity.

back pressure is/isn't a myth, and your correct, velocity and volume are the most important things to keep in mind when making an exhaust system... with too large of a diameter, there's a larger surface area so you lose velocity, but the problem with the stock exhaust is you can't move the volume of air to make the engine run optimally for performance, it's all tuned for emissions and fuel economy from the factory. Cylinder scavenging is brought on by high and low pressure exhaust pulses moving through the exhaust system, and is imperitive to engine performance....

Touge, a 2.25-2.5" system would be fine for your car

-Dan

240sx2nr95 wrote:...and your correct, velocity and volume are the most important things to keep in mind when making an exhaust system...

...a 2.25-2.5" system would be fine for your car

There's the issue...even a 2.5" system has proven to not move enough volume on a big 'ole KA24DE.

If you've seen the 3" KA dynos, you'll see they yielded little to no TQ loss, with big gains in HP up top...and the #s don;t lie.

2.5" is MUCH better than stock...but there is additional power to be found with a 3" system, with no real trade-off.

So I'l ammend "240sx2nr95's" post to say:

Quote »...a 2.25-2.5" system would be fine for your car, BUT a 3" system will be better[/quote] - Brian

I have a 3 inch exhaust on my coupe, RSR exmag, and I gained some power up top, barley noticable, and didn't really lose any down low. Yeah, it's going to be loud at WOT, but it's not ricey. I thought it was when I first put it cause I couldnt hear how it sounded outside of my car, but I let my friend drive it down the road while I listened outside, and sounds nice. Loud, but not ricey at all, kinda mean, you can tell it's no Honda, that's for sure. At low RPM's, it sounds real nice, almost like a WRX with exhaust. If you plan on going turbo or want a 3 inch, I say go with RSR, may be a little pricey, but it's the best catback you can get IMO.

can we have this topic killed please

n/a-2.5inchturbo-3inch

leave it alone now

Cookdaddy wrote:I have a 3 inch exhaust on my coupe, RSR exmag, and I gained some power up top, barley noticable, and didn't really lose any down low. Yeah, it's going to be loud at WOT, but it's not ricey. I thought it was when I first put it cause I couldnt hear how it sounded outside of my car, but I let my friend drive it down the road while I listened outside, and sounds nice. Loud, but not ricey at all, kinda mean, you can tell it's no Honda, that's for sure. At low RPM's, it sounds real nice, almost like a WRX with exhaust. If you plan on going turbo or want a 3 inch, I say go with RSR, may be a little pricey, but it's the best catback you can get IMO.

How's the exmag sound at cruising ?I thought the thing was supposed to be kinda quiet!

With the DC Sports header and Gude High Compression Head the RSR ExMag sounds hella LOUD at WOT!!! I mean I scare the **** out of everything around me! You will also need to weld a new flange on the cat to fit the 3" piping of the RSR. I bought this exhaust because I thought it would be really quiet. My friend bought an apexi exhaust and used 3" piping on his S14. With or without his silencer his car sounds really quiet. I mean he has no issues with cops because it is so quiet. If I had to do it all over again, I would get an el cheapo Ultra Flo and get 2.25"-2.5" piping. I actually had this set up before and it was really responsive on a stock KA24DE. I mean an exhaust is an exhaust and no I don't consider it really making much power as much as shifting the powerband. As my car stands now, there is really a huge loss of low end torque below 3,000rpm, probably from the 3" piping of the RSR and the DC Sports Header. However my high end is killer. The KA24DE never felt so good at high rpm. I am currently installing the AEM EMS. Once this is done I shall post a dyno chart and see if AEM is full of **** or not and if there really is as much loss lof low end torque that I currently feel. I will be changing to MAP and using 370cc injectors. I am hoping to get around 180WHP if the AEM EMS lives up to its claims. We shall see. I will keep you guys posted.

is anyone else hypnotized from the bold print?

anyways...i'm locking this for the fact that not only has this been discussed thoroughly in the past, but the end result is always the same.

back and forth, back and forth.

i will say this though...i'm still waiting for someone to show some real proof that a 3" exhaust does as much harm as some people claim.

-demetrius