matth76

Hi
Will fitting a 3" system on a hawkeye STI or other newage model generally lose a bit of low down torque but gain more top end compared to a 2.5"? Whereas a 2.5" system will have more torque lower down but slightly less higher up? Both systems would be the same design/make, just different bore, both with a decat or sports cat downpipe with full remap. No other mods or just panel filter.

Ultimately I'm interested in what aids low down torque, 2.5 or 3".

Thanks for any info.

ado

iTrader: (4)

Good question
I would like to no the answer to this.

Come on peeps

saiklon

To aid low down torque, port the standard headers. A 3" turbo back exhaust will not lose low down torque and may gain you some top end power as compared to a 2.5". Of course the more power you are running the more top end improvement you will notice.

Increasing exhaust cross-section pre-turbo will almost always lose you low down torque.

saiklon

Double post

greatgonzo

iTrader: (1)

3" will be louder, i know that

Cobra Sport Exhausts

iTrader: (2)

HI,

We have done BHP Tests on both 2.5" and 3" systems... 3" does give extra BHP.
Please see website www.CobraSport.com ( news section )

Thanks

Pete

53

iTrader: (41)

Without mapping 3" does rob you some torque just swapping 2.5-3".

'Higher up', 2.5's don't really have a problem higher to where they're still pushing power, so you want it punchy lower down IMHO.

matth76

Thanks for all the replies guys. The comparison would be both with a remap as they would both ideally be turbo back systems (with decat or sport cat downpipe). So the general opinion appears to be a 3" makes more top end bhp but the torque is shifted higher up the rev range. Whereas a 2.5" will make slightly less power (bhp) top end but the peak torque comes in earlier in the rev range than with a 3" so in effect you get more "response" low down with a 2.5". Have any other tuners on here or people done tests to back this up?

I know a 2.5" is good for big bhp but 3" is better if going for monster power. I'm just curious about mild power up to ~350 and what the torque characteristics are between the two systems, and which one favours low down "response" more.

Thanks again.

danos14

iTrader: (8)

there is a guy on here who tests brake pads (cannot remember his name) he looked into this on the 200sx and found the 2.5" system had better torque.