im getting ready to redo my exhaust on my h22 should i go with 2.5 or 3in.its allmotor with type s stuff and boltons. thanks

 

Are you N/A? nuff said.

 

Doesnt sound like your running a crazy all motor set up so there isnt any reason for a 3 inch exhaust.. 2.5 in will work just fine for what you have.

 

a 3 inch exhaust on a relatively stock n/a motor will do nothing but cause alot of noise. i think i have seen cars lose power on the dyno with overly huge exhausts.

get a 2.5

 

Slightly off topic. But I have never understood this, why would you need a 3" exhaust unless you are running forced induction or a V8. Is it just to be loud/like the sound?

I mean I run a 3" dp to 2.5" exhaust for a quicker spool. Now what is your reasoning?

 

your right, someone correct me if im wrong but, when boosted (turbo wise at least) you want the exhaust gas to exit the car/exhaust rather quickly, due to the turbo being there, and having less resistance against the fins/turbine in general. thus quicker spool etc etc. better boost overall.

a 3 inch exhaust on a stock motor really wouldnt do anything greatly better than a 2.5 really, unless you want the sound of your car to be alot louder. (not something i suggest in VA). but the BIGGER BORE, higher compression motors these use 3 inch collectors on the header, to 3 inch exhaust if one is present, due to the fact of the higher compression and the more flow. but usually have a fine tuned header (smsp, RMF, etc) because the design of the header usually keeps the right amount of backpressure wanted for the n/a build.

 

You are right about the turbo, less back pressure= less resistance&faster spool with turbo. Now if I was running anything bigger than a ko4 I would run straight 3". I just dont understand the n/a cars running 3", it seems to be more detrimental than helpful. If i am wrong correct me, just trying to get some clarification.

 

naw even n/a cars need some kind of good flow of exhaust gas to run its best. (i,e max hp, tq) just to much of a flow of exhaust on a n/a car loses torque and kills the cars perfomance more than it helps. for example....

when i worked at my last shop with the dyno, i put a buddy club spec 2 exhaust on my eg hatch. (its a straight pipe, with one small resonator). true 2.5 inch exhaust.
it picked up hp over the exhaust i had on the car before. but lost tq. i put in the silencer just for shits and giggles and i made more tq than i did before, but lost 2 or 3 hp. but all the 3 inch exhaust i have seen on stock motors dont do shit, but cause the car to lose torque and make alot of noise. but all the n/a guys i have followed in n/a drag racing at least use the big collectors/exhausts but finely tuned headers to make up for the loses the normal motor would lose with a huge exhaust.

 

This maybe a dumb question but since you brought it up ill just ask. What do you mean by true 2.5in exhaust. As in 2.5in piping all the way to the header.. or headers?

 

I am assuming the ID of the headers and flow paths for best/less restrictive flow.