Will a 2.5" system be ok to use with a vf35 on my 01 WRX?

I've had a look at some downpipes and all I can find are 3" downpipes with the 2.5" ends on the that connect to the standard system. But I have also found a 2.5" stainless system that will fit the rest of my car.

Will this be ok for around 340-350bhp (as I think that'll be the max I can get out the vf35)

Or has anyone ever bought one of these
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2.5 will be sound you dont want to oversize the system,and i wouldnt bother with that system,i have never used one or know anyone with one but i wouldnt imagine those flexi joints will last on the up pipe

 

3 inch straight through mate, get a good branded one like magnex (bust) or hks

 

unless he intends on getting a built engine i wouldnt put a 3" on a standard engine,it will do nothing for it performance wise(may even make it slower and more lag than a 2.5" would) just make noise

 

went from 3" which tapered down to 2.5" at joints. to a true 3" and the diff was quality. earlier spool and more grunt. that was a t 360bhp, not sure what difference that would make

 

have heard that is a good set up,i think it was david at api that made the comment

 

It will be noisier, but moving from a 2.5" to a 3" turbo-back system on any turbocharged engine is NOT going to make it slower and more laggy. In fact it will improve things.

The system between the exhaust ports and the turbine inlet are the thing that will make the difference in lag, spool up, outright power etc.

 

on my00 uk i srapped my 2.5" magnex system and went for a full hks 3" supper dragger turbo back (slip jointed) with great improvement and this is with a vf35
currently giving 332bhp @ 1.4 bar with 440s @ 3.5bar
the 2.5" vs 3" exhaust debate does a lot dep on the quality of the exhaust as much as the bore size IMO

 

If its a poorer quality exhaust, would heat wrapping it help?

 

Have a look in here matey, it's second hand but quality stuff for right amount of money...

JPP : TuningParts for Sale

 

A fully decated 2 ½” bore system is adequate up to 350 bhp. After this a 3” system is recommended. Sports cat systems are available but ultimately still limit power compared to a fully decated setup

The above was taken from AndyF's website so I guess a 2.5 will do

 

Agreed, fitted a 3 inch full turbo back system to a classic Ver3 stock Sti (96) and noticed increased lag and lower engine response, go for 2.5 under 350 fly

 

i think if you want to actually get near 350 on a vf35 you would be wise to fit a 3" straight thru.

 

What about the 3.5" im running an APS straight through.

 

i am running a andy f 20g on a 2.5" exhaust only way to be 100% sure on the gains/loses of each would be to do a bk to bk test on the same car same rollers,i do agree it all depends on the system fitted. its all down to future planning and if you are intending to push the car over the 400+ mark in the near future, but as to my personal choice below 390-400 i would go 2.5" (maybe with 3" down pipe only if mods require)anythin above 3"

 

That's interesting, and somewhat surprising. Did you have it remapped for the bigger exhaust as I would have expected the turbo to spool up quicker with less restriction after the turbine?

 

Ive got that system on my Classic, and it's good quality for the price. If you've got £500+ to spend on a zorst, you wouldn't even be looking....

 

I was told by 2 difference tuners that a 2.5" system would not be a major restriction unless you were going over 500bhp which surprised me a bit

 

i had this debate as well about a 2.5" or a 3" for my blob eye sti. i am after 330-340bhp and was told 2.5" is more than adequate up to 350bhp. and my turbo which is a vf35 is only capable of up to 350bhp so i thought i might aswell stick to 2.5" then the thought acured to me that if i did want more power in the future i would upgrade the turbo to a larger unit with supporting mods to around 400bhp but the 2.5" would not support that power so i finnaly got a 3" turbo back milltek system. expensive but i needed to have a sports cat come m.o.t time. so i would say if you arent going to go abouve 350bhp in the future stick to a 2.5" system. try getting a 2nd hand prodrive system they sound awsume much better than the milltek i have fitted now.
hope this helped

 

350 will be more than enough till I see how the car copes. Its been standard all its life.
I think I'll stick to the 2.5". As for turbo's it'll either be a td05 or something from the VF series and a set of 550's
It just feels gutless as the minute, with what power it has running out at 5000rpm. I had a VF28 on my classic and it pulled all the way to the redline.

 

I'm running a vf35, sti pink injectors, 2.5 exhaust system with a prodrive sport cat and am mapped to 344/343

 

That would do lovely!! What sort of mileage does your car have?

I'm more than 90% sure thats the route I'm taking.
VF35
550's
3" downpipe
2.5" system


340bhp is amicable for our roads. I'll need brembo's and suspension after that.


Thanks for all the input.

 

32000, current daily runner but will change that soon with a cheap diesel, scoob will live in the garage then and come out to play at weekends

I'm going down the handling route next

 

Does it make power to the redline? Thats the reason why I want to change the turbo. I like using the revs and my mates WRX has the td04 on it, remapped to 280/300 but it pulls like a diesel. 1bar at 2000 and full boost at 2500 to 5000.
My vf28 was still making power at 6000 on my classic!!

 

I just went from a 2.5" system to a 3" with a 321H
With the H&S 2.5" I was about 398bhp
Just the change to 3" Revolution system and a remap to suit
Aprox 420bhp now.

 

^^^ backs up earlier posts about running a 3" exhaust circa 400bhp, thats quite a difference though!!

Weeebell yes, pulls all the way like a train

 

here are my cousins figures for my99 with vf35
on 2.5" h&s(3"downpipe) 322bhp
on 3" full mongoose 328bhp
both with ome headers/up-pipe
only 6bhp so not a lot in it around 320-330 but both runs were on the same dyno so little improvement