2,5" exhaust too restrictive??
29 July 2004, 09:13 AM
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2,5" exhaust too restrictive??
Hi guys,
A friend is having probs to achieve over 300hp with his
STi8, with Motec M800 ECU (with als and IC spray),
Walbro 255 fuel pump, and H&S decat from up-pipe > back.
1,5 bar boost max, tailing off from approx 5000 rpm.
He's had people tell him the exhaust is the problem, being too
restrictive etc etc. I'd say this is complete B.S. (It's more likely the mapper who is the problem)
It's the regular H&S with up-pipe, 3>2,5" dp, decat resonated mid, and backbox with 3,5" slash tailpipe.
Other factors aside, I'd guess this exhaust system would be more than good enough for about 360hp, and quite OK up to 400hp before any real gains could be had from upsizing to 3 or 3,5 all the way.
Any opinion on this please???
Regards,
Simen.
A friend is having probs to achieve over 300hp with his
STi8, with Motec M800 ECU (with als and IC spray),
Walbro 255 fuel pump, and H&S decat from up-pipe > back.
1,5 bar boost max, tailing off from approx 5000 rpm.
He's had people tell him the exhaust is the problem, being too
restrictive etc etc. I'd say this is complete B.S. (It's more likely the mapper who is the problem)
It's the regular H&S with up-pipe, 3>2,5" dp, decat resonated mid, and backbox with 3,5" slash tailpipe.
Other factors aside, I'd guess this exhaust system would be more than good enough for about 360hp, and quite OK up to 400hp before any real gains could be had from upsizing to 3 or 3,5 all the way.
Any opinion on this please???
Regards,
Simen.
29 July 2004, 09:16 AM
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i would say your absolutely right, i posted about this last week, as i was going to go for a 3" but was told that 2.5" was good enough up to 380 or so.
30 July 2004, 11:28 AM
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You're right. Should not be a problem.
A good 2.5" decat exhaust is nice up to 360bhp
I'm getting 390bhp with 3" bell-mouth decat DP and 2.5" decat catback and rear muffler.
I've seen many STis achieving more than 340bhp with sportcat or decat 2.5" exhausts.
A good 2.5" decat exhaust is nice up to 360bhp
I'm getting 390bhp with 3" bell-mouth decat DP and 2.5" decat catback and rear muffler.
I've seen many STis achieving more than 340bhp with sportcat or decat 2.5" exhausts.
31 July 2004, 04:53 PM
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Exact ! I agree with the previous statement. ^^^^
I'm running the same catless 3" Helix DP with stock catback and yesterday, I swapped it for a 3" Greddy EVO2.
Reading MAF in 3rd gear, I have absolutely the same values b4 / after.
A good DP is the best way to achieve big numbers.
I'm running the same catless 3" Helix DP with stock catback and yesterday, I swapped it for a 3" Greddy EVO2.
Reading MAF in 3rd gear, I have absolutely the same values b4 / after.
A good DP is the best way to achieve big numbers.
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