3" downpipe power increase?, about how much? Options

[easternpiro1]

Hi guys, Ive been wondering how much HP increase do you get when you add a 3" downpipe to your turbo setup? ive been told in the past at least 10hp, but before making a thread i decided to do some searching....

http://www.mr2oc.com/showthread.php?t=2714...horsepower+gain

and now I have a headache...

on our 3s its obvious that a wider diameter exhaust makes room for more power, but ABOUT how much typically?

I actually read 98% of that thread, and while VERY informative, i didnt get a question answered after all the searching.

anybody know the answer?


cheers!

[3WayStunna]

I see and understand your dilemma EasternPiro....There dosent really seem to be much hard concret dyno proof, just alot of talk on how much more PSI a persons engine/turbo setup can run. But i think the general acceptance is around 10-15hp.


EDIT: Ran across this on GTfours.co.uk...

Why do I want to fit a downpipe?

To improve turbo spool up time, increase output power ~15bhp/~15lbft, and to save weight ~9kg. My 205 used to have a fairly noticeable "flat spot" at approx 5500 - 6500, this has now disappeared...

Are there different down pipes available?

There are a few different ways to replace the catalytic converter, you can either make one or buy a downpipe. The only available ones at the time of writing are:

Blitz - a replacement "top section" of the cat. Well made, fits bang on, heavy and will improve gas flow, but if your spending the money you might want to consider a full down pipe.
Hyper Sports and Racing (HSR) - 2.5" pipe, but the wastegate gas path is not as free flowing as the Aussie. Fitment is also crap. I suffered a cracked pipe then a replacement had a warped flange and I had to drill EVERY hole in order to fit the damn thing, NOT recommended.
Hayward and Scott - 3" good alternative to the Aussie, however this is stainless so will last longer, but will be prone to cracking more so than steel as it is fabricated from stainless, but then again it's got a lifetime warranty! An all encompassing solution for you exhaust, as you can get a full 3" system fitted at the same time
Aussie 3" - superb. Good fit, can get a HPC coating as well...thoroughly recommended. Manufactured from steel, corrosion may be an issue long term...An optional extra is holes in the DP so that you can put "stuff" in there later e.g. wideband oxygen sensor
KO Racing 2.5" downpipe - click here to visit their website
C2 Power - quality seems fine but the closest stud to the radiator does not fit...
XS power / JJ Japcars / SS Autochrome - a little early to say but these seem to be okay

Also i can understand a person purpose on research, but considering there is little to say that adding a 3in downpipe is bad why not just go for it. ...also i do have some help for you. I remember there was a thread on GT4OC that actually did explain the differnce in terms of horsepower btwn a 2.5in, 3in, and 4in downpipe. Maybe you can move your search there?

This post has been edited by 3WayStunna: Nov 29, 2011 - 1:51 AM