2.5" exhaust

[akaye4000]

I've just dropped my car off for mapping and they said because I've only got a true 2.5" exhaust from turbo back and screamer pipe I'm limited to 300HP and I need a 3" to get more is there any truth in that as I thought loads of people where running over 300 on 2.5" exhausts and also other cars like Impreza's run over 300 on 2.5" exhausts?

[Phil]

What exhaust have you? And have you the stock bottle neck at the bottom of the downpipe removed?

[akaye4000]

Wepr true 2.5" downpipe with bottleneck removed and adapted my blitz nuf spec, removed pipe from flex forward to 2.5" pipe to same flange as downpipe so no step down

Edited March 22, 2016 by akaye4000

[Phil]

Should be grand

Phil

[jayc-glanza17]

Thats rubbish mate..

Granted i have a larger exhaust but my downpipe is 2.5 inch never had issues.

My mapper had over 430bhp on his 1.6 106gti and that was 2.5 from downpipe to backbox..

[Phil]

Yup exactly.

Pretty sure there is a website that gives correlation between exhaust size and potential hp

I'm 375 and using 2.25 exhaust

Phil

[akaye4000]

Thats rubbish mate..

Granted i have a larger exhaust but my downpipe is 2.5 inch never had issues.

My mapper had over 430bhp on his 1.6 106gti and that was 2.5 from downpipe to backbox..

Nearly went with your mapper but couldn't justify the extra 150

[AdamB]

It's all relative to engine size, it's not just about size vs bhp.

2.5 inch will be fine, but no doubt you'll gain more by changing system.