2.5 VS 2.25 EXHAUST N/A
 

Hi guys. As this is my first post I hope this is the right place to ask.. Now here's the thing. I will upgrade my exhaust and I will keep my car NA. I searched a lot on this topic and couldn't find any good info on sport exhaust with same diameter as stock piping. Nearly every aftermarket exhaust is either 2.5, 2.7 or 3 inch. Since some people have seen nearly the same gains with gutted stock header vs 2.5 catless I want to know your opinion on this. Is the upsizing a must or can you see a good gains with 2.25 outlet catless header/ sport cat fp? For example I know Supersprint and Japspeed make 2.25inch header/exhaust but I couldn't find any good dyno/testing on. Could it even be benefitial to stay stock diameter? oh.. In any case car will be tuned with ecutek after I decide on a specific exhaust. The goal is power increase to 250bhp with i/h/e+billet power blocks+tune

Cheers guys!

If you upgrade headers and do custom tune, there is not much to gain from BPB. I would also add to list of changes E85. I suggest to read this thread, probably will clarify few questions. Also NA target of 250bhp is too high, you won't reach it. If it's a goal, go straight away for forced induction, eg. supercharging, skip spending on intake/exhaust/header bits.

You'd need some serious work done on an n/a fa20 to get 250bhp, not to mention some serious cash, if it would even be possible. Go supercharged or turbo, as churchx said. It'd be cheaper and easier.

Check this guys build out. http://www.ft86club.com/forums/showt...ht=Ultimate+NA

Thanks guys for replies. But I wonder why the Crawford power blocks won't work. Aren't they supposed to make most impact on an NA car? Also 250bhp is just the optimistic number.. I dont care if I can get 230 or 250. It just need a bit more kick in the ass and also I don't want to go fi as I don't really need power (just a bit). I will focus my mods on suspension/handling. see my roads pics below. With FI on these roads I will crash or most likely run my car on lower rpms which negates the need of fi and is also not good for a car on the long run.

Oh and to avoid confusion my goal is 250hp on the motor and NOT on wheels. So don't mistake whp for crank hp.

Hope you have racing experience, good luck with your build.

Read the link churchx posted and it will explain why BPB don't do to much after you install headers on an NA.

proffesorGLIVE: oh they will work, from reviews they not just shift powerband to lower revs, but also rise a bit overall area under curve. But it's more noticeable for almost stock everything. If you upgrade all the intake/exhaust, imho gains from intake spacers are very minimal, if any, resulting it little bang for a buck. Also you can get more power at higher rpm-s with proper tune slightly rised rpm limit, even more so with use of better petrol or eg. E85 .. but will you have that, if intake spacers like BPBs lessen power at top end with powerband shift? Good header gives gains in midrpms too, and also may fix "torque dip".
P.S.
If you aim to stay NA, be ready to spend a LOT, as NA power gains are expensive and you will also hit diminishing returns. Read the thread i linked, it should tell what gains are expected. I'd say .. if you insist on NA, get some good catless header (eg. ACE 350 Type A) + tune, add aftermarket drop in airfilter and leave it at that. Put rest of money in suspension and/or track days/HPDE and so on ..
P.P.S.
Road looks very interesting to drive through :)

Ok.. I think I am either unclear (most probably) or the numbers are confusing.. I don't think you need any serious work to get 230 to 250 crank hp. thats 180-200 whp. people have reached those numbers even without flex fuel I believe. And numbers are not really important to me. My question is will stock sized piping with removed or hf cats give me more or less same results as 2.5 inch exhaust system. Some people had good results with gutted stock cats so maybe I can save some money and go for Japspeed instead of tomei. 500eur saved there ;) for sound I don't care as long as it's not too loud.

@churchx

Thanks! see.. you got me closer to my final decision already :) so power blocks are out I guess.. shame. So would a Japspeed header be a good option as I have a good deal on it? or would high end header be worth the extra cash? It is also my first car for modding everybody so excuse my lack of knowledge.. I dd this car and a bit of driffting so no race applications here whatsoever. Also there is so much info about exhaust that is contradicting.. some say fp will give you nothing, others say cat back will give you extra hp, others say no, some say gutted header is just as good as any aftermarket one and some say you need a high end header to make a good tune. So now I don't know what the hell will I choose :) So since my goal is not a specific number I can sacrifice a hp or two in the name of money saving. I don't want cheap out and buy crap and I don't want 2000eur header that will give me 3whp over the crap one. I kind of hesitated to open a thread cuz there is a ton of info about this but the results and opinions vary from thread to thread

The ace header (with a tune) would be more than 2 or 3 hp. There is a thread about them, it's on the first page near the top of the engine, exhaust, trans subsection you posted your thread in. Pretty good info there, the most attractive thing about ace is how it levels the power band and essentially eliminates the torque dip.

Kinda got derailed a bit I guess, since the title of your thread is about the diameter of your exhaust. I read somewhere about a guy who had built a lot a race corvettes, and all he uses are 2.25 exhaust. A good header is more about the flow and how it lets the engine breath. You could have a 3inch exhaust, but if it flow like crap then a well designed 2.25 would see more gains. If for the sake of saving money, and your not looking to build a racecar, then gut the stocker and get a openflash tablet to tune, and put the rest in suspension.

A decent header, aftermarket air filter, and a quality tune will get you close to 200 whp on their own. Ace makes great headers, and CSG ships worldwide. With a Delicious remote tune, you should be pretty well set.

get an aceheader & good tune. O.O Done! :D

replace the intake panel filter too the stock item is pretty restrictive
but that , a manifold and a low back pressure exhaust and a good tune will get you 220+Crank