Experience with 3" exhaust on N/A

[d4vech3n]

I read all the arguements and reasoning about 3" exhaust negatively affecting performance on a nearly stock KA but then there are threads where people claim to have no loss of lowend and actually gained top end.

I want to hear experiences of people who have switched from an oem exhaust set up to 3" catbacks on an stock or nearly stock KA24de. It'd be nice if there were some E.T's since thats a pretty good indicator or dyno sheets which i doubt many will have for just swapping exhuasts.

To start off, my friend bought an Auto s14 that is completely stock aside from the 3" exhuast starting right after the cat. His car runs 18 seconds and 17.78 is his best. When sitting in his car, it feels like nothing is going on until 4k rpms.

Any other input?

[Phlip]

You mention having seen posts in reference to the positives/negatives of going with a 3" exhaust on an N/A engine, but would now like people to specifically go out of their own ways AGAIN to explain their own personal stance on the whole "too big and you lose backpressure" argument? I just don't think that you have yet searched effectively and PROMISE that you will find all that you seek in this very forum when you do.

[Maeda]

The car will feel like nothing is going on stock or 3 inch. =)
Get the 3 inch and put one of those new fangled smog pumps that pump out exhaust while pushing air into the intake and you'll be set.

You won't lose bottom end, and you will gain a considerable amount of response on the top end... but it'll still be n/a...

[Dousan_PG]

yep
did 2.5 or something
and 3" on KA
would do nothing less then 3"
it ruled
espeically putting out a nice good 115+ decibels
nothing like your ears ringing at the track..with the helmet on
haha
good times.

[papershot]

theres a thread on freshalloy that has a dyno sheet before and after a 80mm exhaust.

if you want to reduce your times get rid of the auto tranny.

[d4vech3n]

that was a friend of mine. I have a stock s14 exhaust on my car (it's a stick too btw) and it rattles way too much around 2500 to 3000 rpms so I was thinking about just going with an 3" exhaust.

Philip: I don't want people to reexplain that entire thread over. I wanted to hear experiences. That thread was simply peoples theories and explanations of what they feel should and would happen but as exemplified by this thread, people claim to gain better times from 3".




Also... does 3" really kill gas mileage?

[zero.counter]

Originally Posted by d4vech3n

Also... does 3" really kill gas mileage?

Where the hell did that come from?

[m0rex]

Originally Posted by zero.counter

Where the hell did that come from?

lol thats teh funny.

Anyways keep this simple because i want to know too dont start any arguments i just want an answer if anyone that has had a 3". I have a ghetto rigged exhaust that i made out of piping and an aftermarket exhaust that i found in the junkyard that aint that bad but it feels like it boggs me down a lot.
.. But sounds nice with huge backfire everytime i let go off the gas.

[kandyflip445]

I have a 3" on a NA car. It's not too loud and definately pulls harder. No dynos from my car though. It's the same one that was on Alex's s13. He gained, IIRC, 15hp in places. Gas mileage is better with it. I'm with PHLIP on this one. You need to search AND read. It has more to do with exhaust gas velocity than backpressure. Happy searching dinky.

[Ranger_Man]

Originally Posted by d4vech3n

I have a stock s14 exhaust on my car (it's a stick too btw) and it rattles way too much around 2500 to 3000 rpms so I was thinking about just going with an 3" exhaust.

Just take off the heat shields and that rattling will go away.

In other news, I never ran my car at the track when it was 100% stock but I did run it when I only had a cone filter and the N1 single exhaust. I managed a best of 15.5 @ 88 or so mph. With the addition of a hotshot header I managed a best of [email protected] mph and I also managed to anger all of my neighbors when I would come home from work at 2am.

[m0rex]

[email protected] for reals? Sounds too good to be true. Unless you are a really good driver and have some really good rubber... or what?

[d4vech3n]

This is the n1 single 3" right? Not a custom piping with n1 muffler? If so then that is pretty good, sounds like you gained more than lost.

I have an offer for a pretty nice deal for an used apexi n1 exhaust but the resonator has been replaced with regular piping. How do you think that will affect it? I don't care if it's too loud but don't want it crazy loud.

[MakotoS13]

for the price of a decent exhaust you can put a 5spd in that car and take at least a second off its time...

[d4vech3n]

Again, not my car and this kid is very stubborn about that. I gave up trying to convert him, he agreed that if his tranny blows then he'll get the swap.

Lets try to keep this soley on 3" exhuast on NA and answer questions without deviating from the first post too much. I'm posting this more for my sake. This n1 single with no resonator I plan on buying is very tempting but after my friend's experience, I don't know what to believe about 3" exhaust and the way it affects performance. I was hoping this forum will sway me in the right direction.

[Ranger_Man]

Originally Posted by d4vech3n

This is the n1 single 3" right? Not a custom piping with n1 muffler? If so then that is pretty good, sounds like you gained more than lost.

I have an offer for a pretty nice deal for an used apexi n1 exhaust but the resonator has been replaced with regular piping. How do you think that will affect it? I don't care if it's too loud but don't want it crazy loud.

Yes, mine is the normal n1 single, not some hack job with a n1 muffler. It will be loud but if you keep your rear interior it won't be horrid.

Yes [email protected]. Stock wheels with 205/55 ES100s on them. I was cutting 2.200 shorts.

[theicecreamdan]

Originally Posted by d4vech3n

This is the n1 single 3" right? Not a custom piping with n1 muffler? If so then that is pretty good, sounds like you gained more than lost.

I have an offer for a pretty nice deal for an used apexi n1 exhaust but the resonator has been replaced with regular piping. How do you think that will affect it? I don't care if it's too loud but don't want it crazy loud.

It sounds badass, had it on my S14 and never knew what it really sounded like until I sold the car. its so beautiful sounding.

[RBS14]

I too have gone from stock to 3". Didn't loose low end and gained response and top end. Kind of like when I put my silencer in, the car is slow and has less response. then I take it out and it's much more fun to drive. I wouldn't bother with anything less than 3" on a KA in N/A or FI form.

[BSeay]

i went from stock to 2.5" to 3" i can tell you the 2.5 keeps a little low end, but the 3" makes the bitch move above 4k

but i have injen intake and RSR exhaust....


And all of these are with an intake, i dont know what the stock airbox feels like anymore...

oh and the 3" backfires somewhat (i call it a garble)

[C.]

here's a dyno that was posted a while ago in freshalloy.com.

Before and after, 5Zigen's Pro Racer EX-III A-Spec, 80mm (3.1")




The reason why he ran such a shitty 1/4 was because of the auto tranny. I remember when i got my first s14, i almost cried when i realized how slow it was; i was getting consistent 10.1 0-60, even power braking it, the best i could do was a 9.73.
the moral of the story? go stick or go home… period.

[Blues13]

That's a nice performance gain for a NA car with just the exhaust.

That 10.1 0-60 is just sad... didn't kno the auto was that bad.

[Dee240sx]

I think it's pretty much PROVEN that a 3" will make more power on a higher displacement 4banger like the KA24DE then a smaller diameter pipping exhaust would.

The biggest concern for many people including myself, is the noise a 3" exhaust will create on an N/A. I know you can run a silencer but then you're hindering your gains on the exhaust.


For the noise problem alone, I'm 95% I'm sticking with a 2.5in exhaust.

[90RS13]

I think it's pretty much PROVEN that a 3" will make more power on a higher displacement 4banger like the KA24DE then a smaller diameter pipping exhaust would.

It's been proven that a larger diameter exhaust makes more power on very small displacement engines. A honda B16, N/A, with a 3", 3 foot long pipe (and that's it), after the secondaries, made 13 hp. As long as you have a good header design, run the biggest exhaust your app, or ears will allow.

[theicecreamdan]

apex'i N1 3" with no resonator and a test pipe isnt all THAT loud...

[justinhustle]

no cat, custom mandrel bent 3 inch with turbo sized hks carbon ti

no lost bottom, no lost anything

loud as hell n mean as fuck

[papershot]

Originally Posted by Dee240sx

I think it's pretty much PROVEN that a 3" will make more power on a higher displacement 4banger like the KA24DE then a smaller diameter pipping exhaust would.

The biggest concern for many people including myself, is the noise a 3" exhaust will create on an N/A. I know you can run a silencer but then you're hindering your gains on the exhaust.


For the noise problem alone, I'm 95% I'm sticking with a 2.5in exhaust.

running a 2.5'' would be just as bad as constantly having the silencer except you couldn't remove it. 3'' isn't THAT loud on N/A unless you have like a DD style exhaust.

[S14DB]

N1 style Mufflers will ALWAYS be loud no matter what size they are. If you want something quieter go with a normal muffler style.

My 60 to 80mm experience:

[SpdElemts]

I have a Apex GTspec on my kade, i dont think its full 3inch piping but this thing sounds mean and pulls like no other stock 240s with exhaust i ever drove.

[Yoshi]

Originally Posted by papershot

running a 2.5'' would be just as bad as constantly having the silencer except you couldn't remove it. 3'' isn't THAT loud on N/A unless you have like a DD style exhaust.

which is loud even on a turbo car

[019]

Originally Posted by S14DB

N1 style Mufflers will ALWAYS be loud no matter what size they are. If you want something quieter go with a normal muffler style.

My 60 to 80mm experience:

i assuming these were done on different days? did you change anything on the car btwn the 2 dynos? this is the first good comparison i've seen of a 2.5" vs 3", so i just wanna get some info on it

[Maeda]

Originally Posted by Dee240sx

For the noise problem alone, I'm 95% I'm sticking with a 2.5in exhaust.

Unfortunatly the noise problem seems to be a KA problem.

Almost every other SR i've heard has been quieter then my KA n/a or turbo-ed with an aftermarket exhaust... -_-