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2.25" or 2.5" Exhaust?

Posted: July 17th, 2008, 5:45 pm
by neli_nael
give me your opinion of which is better for performance? i don't get this whole exhaust thing. i heard 2.5" because 2.5L but don't get the reasoning. will 2.25" restrict air flow? i have seen different people with either 2.25" and 2.5".

Re: 2.25" or 2.5" Exhaust?

Posted: July 17th, 2008, 6:53 pm
by marcdh
well my local SS exhaust makers said 2.5" was overkill for ZE/200hp, and that you would lose power throughout the lower range. They reckoned 2.25" would suit it best and still allow easy breathing up to 300hp as I said I may turbo. The main guys been making performance exhausts for 20+ years, seemed confident about it!

Re: 2.25" or 2.5" Exhaust?

Posted: July 17th, 2008, 7:06 pm
by fowljesse
I've been thinking about this, too. I have 2.25, and it is the strongest pulling ZE known, out of about 15, to the guys who have driven it. I recommend 2.25 with the least restrictive components that your ears can handle. I recommend Flowmaster.

Re: 2.25" or 2.5" Exhaust?

Posted: July 17th, 2008, 8:01 pm
by Mooneggs
if you search around there are some great arguments *ahem I mean threads about this regarding backpressure...

I personally have 2.5" but it's not mandrelly bent so in some places it's probably 2.25"...

Re: 2.25" or 2.5" Exhaust?

Posted: July 17th, 2008, 8:41 pm
by blaudust7
2.5 in. on my K8. Its really your personal preference.

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 12:08 pm
by neli_nael
marcdh wrote:well my local SS exhaust makers said 2.5" was overkill for ZE/200hp, and that you would lose power throughout the lower range. They reckoned 2.25" would suit it best and still allow easy breathing up to 300hp as I said I may turbo. The main guys been making performance exhausts for 20+ years, seemed confident about it!
fowljesse wrote:I've been thinking about this, too. I have 2.25, and it is the strongest pulling ZE known, out of about 15, to the guys who have driven it. I recommend 2.25 with the least restrictive components that your ears can handle. I recommend Flowmaster.
Cool, I'm getting a new exhaust system by end of the year so this definitely helps. I think I'm going with 2.25". :D

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 1:33 pm
by blaudust7
Yeah I guess 2.25 would be suitable for the KLZE, but since I have the K8 I went with 2.5.

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 1:37 pm
by neli_nael
blaudust7 wrote:Yeah I guess 2.25 would be suitable for the KLZE, but since I have the K8 I went with 2.5.
i dont follow you but i guess its ur preference, what do you have in your car?

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 2:54 pm
by onlytrueromeo
2.5 on k8 w/ no boost is WAY overkill, lol that makes no sense to say 2.25 works on ZE but 2.5 is better for k8

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 3:25 pm
by hgallegos915
On the dyno, i gained hp at 2.5 inch piping, like 3 and lost like 9 lbs of torque!

:S



sucks :S


only good if u going turbo

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 3:26 pm
by ninjajim4
Mooneggs wrote:if you search around there are some great arguments *ahem I mean threads about this regarding backpressure...

I personally have 2.5" but it's not mandrelly bent so in some places it's probably 2.25"...
thats the same reason i went with 2.5 myself. it's easier for parts too, headers etc

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 4:30 pm
by neli_nael
hgallegos915 wrote:On the dyno, i gained hp at 2.5 inch piping, like 3 and lost like 9 lbs of torque!

:S



sucks :S


only good if u going turbo
ever dyno 2.25"?

Re: 2.25" or 2.5" Exhaust?

Posted: July 18th, 2008, 5:32 pm
by hgallegos915
no.. it was stock exhaust vs the 2.5 exhaust tho.. Im sure 2.25 would be in perfect synk with a n/a engine.

Re: 2.25" or 2.5" Exhaust?

Posted: July 19th, 2008, 8:06 am
by marcdh
hgallegos915 wrote:no.. it was stock exhaust vs the 2.5 exhaust tho.. Im sure 2.25 would be in perfect synk with a n/a engine.
Sure feels it :) I said I wanted 2.5" as I may go turbo and they talked me out of it (even though they would have got more money out it! :o ) Would love to have the money to burn on dynoing both, but I don't! I reckon as Hec's dyno showed 2.5" will create a bigger peak HP at higher revs, but loss of torque throughout the powerband/narrower powerband.

Re: 2.25" or 2.5" Exhaust?

Posted: July 19th, 2008, 2:02 pm
by hgallegos915
yeah and torque is what kills our fellow hionda gsr dudes. They have high hp but they have like 134 torque.


160 torque is alot compared to them :D