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

[Rav4Race]

Hi. In my Opinion;

Having a bigger downpipe will just help your engine to breath easier, in other words, a better flow compared to stock. But having a 3" downpipe will just give your engine more potential to make more power later. To make more HP, an optimum use of your new downpipe, would require an aftermarket manifold and a boost controller. Because such modifications will make u face other issues like boost creep or overboost and fuel cut. You may also like to get a better turbo and if possible a standalone ecu so that you take the maximum advantage of your new modifications. Such modifs should get u, I'd say like 50-60 HP (all together)!!!
But getting only the downpipe may only allow like 4-5 hp.
Downpipe + manifold may get u around 12 hp.
Downpipe + Manifold +decat may get u around 15-20 hp.
Downpipe + manifold + decat + new turbo + ecu may get u around 50 hp.
Downpipe + manifold + decat + new turbo + ecu + injectors may get u around 60-100 hp (depending on your tuning and engine capacity).

You may also modify step by step like i am doing, take ur time and get the maximum of your investment in the future. But you will need to tune your boost.

On my side i have bought a 3" downpipe and a manifold + decatted. But I had to tune the engine since I was reaching fuel cut and overboost on only 4500 Rpm.
I am taking my time but will surely get the other modifications as soon as i get some $$$

[Smaay]

the larger downpipe isnt giving you more power, its allowing your turbo to work more efficiently, it will raise the boost level which raises the power

[presure2]

There is a dyno sheet running around on mr2oc that shows a berk tech 3" vs a ko racing 2.5" dp.
The berk made more power everywhere.
Can't remember the #'s.

[easternpiro1]

thanks guys! i had a feeling it would be about 10-15 hp, i just wanted to be sure. I will have a def answer once i get my car back, I remember on the stock downpipe with 3 inch (NOT mandrel bent) Exhaust i made 266whp on 15lbs. I will be using a modified 3 inch exhaust with mandrel bent 3 inch exhaust... hopefully no boost creep issues ensue

[injection]

I have a full 3" exhaust, 3" XS Power DP, and a custom Ram Air Intake System with K&N cone filter in the mouth of the bodykit where fresh air hits it straight on, and im at a place where im trying to bring my boost down! with the help and generosity of others on this site, ( 6GC ) just to give you an idea, I have to let off at around 5700rpms cause I will, not might......hit fuel cut..

[cjh4l22]

now we just need someone to make a 3" front pipe! like NOW!

[easternpiro1]

man i swear there needs to be a like button for the comments being made! ummmm can u show me pix of that intake?

[injection]

Yeah sure, hopefully I can upload them....have troubles for some reason, if I can't, I will post I'n my profile pics, that I know works, will let you know on this post....

[PhoenixTech]

Allow me to shed some light on this. Prior to finding out that Matt's engine had a bad head gasket, and then in turn needed OS pistons, the engine held 18psi perfectly with no boost creep. VERY VERY strong pulls all the way through the RPM band, even though 1st, 2nd and initial part of 3rd gear are utterly pointless. (Matt, you need wider tires, 225s ain't cuttin it ) We are controlling the boost via an AEM Tru-Boost gauge/controller. Also, Matt's exhaust is 3" downpipe to 3"...um...."where-the-cat-should-be" back system. Very free flowing exhaust. With that itty bitty stock turbo that's currently on the engine, there was no surging, or boost creeping like you see on a 1JZ or 2JZ with a full 3" exhaust. With Matt's car properly tuned, and with the water meth, we should see 285-295whp at a "reasonable" amount of boost.

-Cam

[cjh4l22]

SO does Tweak'd Performance have any interest in making us all a 3" front pipe? to get all of us 3s swappers from downpipe and past the necessary flex? under oil pan, and over subframe section? I think it would be genius!

[Neon90424]

that section of downpipe...that goes down twists up and back down from the subframe is a real pain in the !$*(&!@$( to fab...took the exhaust shop like 3 hours just to make that part...to the flex pipe

[Island_Racer]

hey guys, these people made mine and i love it to death, its not on their site but if you contact em (email or call) and tell em 3S-GTE front pipe (and decribe it however u like) they will do an amazing job...i forgot how much i paid but i guarantee they have the design and stuff. I connected mine to a c-one 3"exhaust system (no longer made i think) but it lines up perfectly and everything.

http://www.haywardandscott.com/

here is a pic of it....(the shiny set is theirs and fuddy looking one is stock.....front pipe specifically is on the right)




and another pic



This post has been edited by Island_Racer: Jan 19, 2012 - 8:06 AM

[delusionz]

Most GT4s ex-japan are fitted with 3" aftermarket systems from the mid section back to the tail, as mine was, the standard portion of exhaust with the flexi and mini resonator tube tappers down to 2 1/8 inches, which i had the entire lot replaced with a 3" system from the back of the turbo through to the tail and it barely made a difference on the stock turbo, pound for pound it was a little faster to spool up, acceleration was a little bit better, car weighed a little bit lighter, etc....

in itself not so much gain, a full 3" system is just good preparation for when you get a big turbo, and in that case your better off going 3" cat-back and only getting the 1 downpipe made the day you do upgrade turbo & manifold

[delusionz]

I must say, the engine roars alot louder with a 3 downpipe & 3 full exhaust -- on boost you hear the separate tone of the motor as the wastegates open up with the downpipe

This post has been edited by delusionz: Mar 28, 2012 - 10:55 PM

[UndaGrwnD]

hmm on my old car, gen2 3SGTE RC...a 3'' ebay downpipe and a custom made 3'' exhaust made a huge different. with the stock ct26 turbo i got 250bhp. when i changed to the ct20 turbo (gen3 turbo) and the boost was increased i managed to get 320bhp...and that was with the gen3 turbo and the basic BPU.

so i think with the st205 with a BPU (3''dp , 3''exhaust, intake, 1.0bar boost) you should get near 300bhp or even more.

[Soulend]

I haven't dyno'ed my car yet, but it is interesting that I could have a 15-20HP gain with my set up. just running a berk 3" downpipe, 3" full exhaust with no cat and a Magnaflow at the end.

I don't know how I pass emissions with an OBD2 check but *shrug* just glad I do.

Kevin

[delusionz]

hmm... 300+ is quite wishful, i think those levels are above fuel cut level with some kind of water injection safeguard,

http://www.youtube.com/watch?v=EuAdAhXlH98...e=plpp_play_all

these guys are struggling to push past 250 hp atw which in itself is an increase probably max boost 17psi before cut since factory is just 250 at the engine

[Culpable04]

250AWHP at 17 psi is not the same as 17 psi on a Front wheel HP, the drivetrain loss is a big factor here, 3rd gen 3s make right around 300 HP at 18 psi ( 2WD )



This post has been edited by Culpable04: Mar 29, 2012 - 3:16 PM