Quick question bout exhaust size..

[Ek4Vtir]

Hi guys..I'm planining on getting xforce catback system with twin-loop muffler in a few weeks but want to be sure on the size of the pipeing from the CAT to the muffler.. The mechanic told me to get 2"1/4 inches to have good gain.. Anything after that you might lose power than gain.. It's gonna be made of mild steel not stainless if that matters too much..since you guys have experience with b16a engines it's good to make sure what would be best :) bump!

[55EXX]

2 1/4 is spot on for near stock b16. expect a solid gain up top and loss down low. i was surprised how much i lost down low but its worth it for the up top ;)

[Ek4Vtir]

Kool thanks for the tip, would headers / high flow cat solve the lower end loss? or would there also be some sort of loss down low so you can gain something up top? no way to get power all rounder? lols

[Limbo]

decent headers will gain abit of low down.
I used the JDM 4-1s and they gave me a good all round power gain on 2 1/4
Got a steel cat, 1 reasontor & a decent muffler (i used magnaflow).
Very quiet and great gain all thru.
P.S 4-1 make a swooshing noise, its normal. The steel cat only emphasises this.

[Ek4Vtir]

I see kool thanks for da tip buddy :) can't wait. H
Hmm on average how much kwatt does an full exhaust system give? I know it depends on the product aswell but just a rough estimate?

[55EXX]

4-2-1 headers are tuned to give more low end gain. 4-1 is pretty hardcore and aim tuning wise for up top gain even more so.

mini hi jack. legal issues aside, would there be more gain from metal cat or 2 1/4" (match existing exhaust diameter) straight through pipe welded into existing cat? Illegal i know but this not for road car. Where would differences be seen? straight pipe gain up top? down low? etc no guesses please.

my guess would be

Cat - boost down low, strictly guessing, due to grouping of pulses closer together from increased flow restriction
Straight pipe - up top, strictly guessing, from decreased resistance boost up top. but straight pipe would not disturb the exhaust pulses less, so bottom end gain possible?

[saikou27]

4-2-1 headers are tuned to give more low end gain. 4-1 is pretty hardcore and aim tuning wise for up top gain even more so.

mini hi jack. legal issues aside, would there be more gain from metal cat or 2 1/4" (match existing exhaust diameter) straight through pipe welded into existing cat? Illegal i know but this not for road car. Where would differences be seen? straight pipe gain up top? down low? etc no guesses please.

my guess would be

Cat - boost down low, strictly guessing, due to grouping of pulses closer together from increased flow restriction
Straight pipe - up top, strictly guessing, from decreased resistance boost up top. but straight pipe would not disturb the exhaust pulses less, so bottom end gain possible?

i read an article based on a civic. they tested the stock cat against a high flow, steel cat and test pipe.one after the other on a dyno. the results were +3whp for the high flow, +6whp for the steel cat and +7whp for the test pipe. plus when theres no cat its illegal and sounds raspy and only gains 1hp. so go for a good steel cat:thumbsup: