3 inch exhaust too big?

[bmxruler4130]

i found an exhaust (i only have a weld on muffler) thats in my price range, but its got 3 inch piping. ive been told that the 3 in is only for turbos, because there wont be enought back pressure and ill be loosing more hp than gaining? it seems logical i guess.

[special_K]

Yes that would probably be too big for a N/A motor. You would lose a decent amount of torque. The ideal exhaust has no backpressure but it needs velocity. Thats why if you go too big you lose velocity + power.

[96_S14_SE]

Its not that big of a deal and leaves room for ugrades later.. Youll still gain witrh a properly designed 3" piped exhaust. Myself or any other s-chassis owners Ive talked to had anything bad to say about the apex-i N1 that is 3 - 3.25"

The torque loss is minimal if that , and iirc is only in certain area of the bands in our cars as well. Its been a while since Ive seen a dyno sheet of stock vs N1, so I cant be more specific.

I would be more concerned about the design of the unit then the 3" piping.

[bmxruler4130]

http://cgi.ebay.com/ebaymotors...10368

this is the exhaust i was lookin at... any good? i looks decent.

[Former_240_s14]

3 inch is too big for a ka non turbo. i would suggest 2.25 or 2.5.

hope this helps.....

[propain]

I have an Apexi Dual N1, and while i didn't notice much of a gain from putting it on, i didn't notice any loss either.

The reason i chose that exhaust was because i'm going to be putting in an SR20 soon, and aesthetically i like it too

[C-Kwik]

I didn't notice any loss that I could feel when I had a 80mm exhaust on my KA. Keep in mind the stock Cat was still in place and probably reduced flow enough to keep velocity before the cat high. Going with headers and no cat would probably cause a loss of low-end with an exhaust that big. Expect a 3"+ exhaust to be a little bit louder though. They were intended with turbos in mind and turbos already have a side effect of reducing exhaust noise slightly, so this may have been a factor in design.

[djtodd]

I agree that 3" is probably too big for a N/A KA.You could probably pull it off without too much of a performance hit with the cat still in place, but still, unless you plan on going turbo later, I'd go with a smaller system, probably 2.5.

[bmxruler4130]

what do you think is better 2.25 or 2.5i plan on cams, and port and polish

[djtodd]

2.5 is good for a n/a, watch out though. 2.5 is illegal in some areas and if enforcement is tight you might get stuck!

Although I must admint I've never known anyone to be ticketed for exhausts being to large...to loud maybe, but that's another matter

[180fan]

3" is too big for N/A unless you're running some nascar motor in there...as that's what they're using for their N/A cars. Ha ha ha. Well other than that, you're more likely than not gonna lose power from the lower exhaust temp from the huge piping thus you reduce the scavenging effect. If you're gonna stick with N/A go with a 2.25 to 2.5 max. If you're turbo'ed then go with a 3" as you'll need that extra space. Only other thing I can think of that might reduce some of that temperature loss would be thermal wrap along the piping from the manifold all the way down to the base of the exhaust canister. I've seen this done on many N1 race cars and I'm sure there's a good reason for it.

I'm running a 3" pipe and noticed that the power band shifted to the higher rpms and noticed that my low end has diminished noticiably. Currently my motor's N/A but I'm still in the process of building up the rest of the car and it's other systems before I dump in a SR. But I'm still looking into some thermal wrap for my entire exhaust system none the less. Something to think about. If I get around to doing it soon, then I'll post up if it's worth it or not.