akaye4000 Posted March 22, 2016 Share Posted March 22, 2016 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? Quote Link to post Share on other sites
Phil Posted March 22, 2016 Share Posted March 22, 2016 What exhaust have you? And have you the stock bottle neck at the bottom of the downpipe removed? Quote Link to post Share on other sites
akaye4000 Posted March 22, 2016 Author Share Posted March 22, 2016 (edited) 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 Quote Link to post Share on other sites
Phil Posted March 22, 2016 Share Posted March 22, 2016 Should be grand Phil Quote Link to post Share on other sites
jayc-glanza17 Posted March 22, 2016 Share Posted March 22, 2016 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.. Quote Link to post Share on other sites
Phil Posted March 22, 2016 Share Posted March 22, 2016 Yup exactly. Pretty sure there is a website that gives correlation between exhaust size and potential hpI'm 375 and using 2.25 exhaustPhil Quote Link to post Share on other sites
akaye4000 Posted March 22, 2016 Author Share Posted March 22, 2016 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 Quote Link to post Share on other sites
AdamB Posted March 22, 2016 Share Posted March 22, 2016 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. Quote Link to post Share on other sites
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