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Old 01-24-2003, 08:06 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #1 (permalink)
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how much hp does a catback exhaust system add?


im not a believer in exhaust systems other than it's just all sound and no added hp - well maybe 2-5 hp tops. i rather add headers and do something before the cats than add something after it. but thats for my other car. for the dsm say, i add a greddy catback or an rsr catback, how much power will i add? i want to hear from people who added them and dynoed to prove it.

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Old 01-24-2003, 08:36 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #2 (permalink)
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On a turbo car, the exhaust system and how free flowing that exhaust is is very crucial to the performance of turbo-charged vehicles.

I've hard of people adding upwards of 20 horsepower with 3 inch downpipe, test pipe, and 3 inch cat-back, i.e. 3 inch turboback exhaust.

Some will say they've seen more, so we'll let them add their .02 cents too.


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Old 01-24-2003, 08:38 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #3 (permalink)
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Thanks for the insight cucumber. im off to get my exhaust now.
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Old 01-24-2003, 08:40 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #4 (permalink)
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Quote:
Originally posted by c5chris
Thanks for the insight cucumber. im off to get my exhaust now.
Have fun Chris, I know my goal with my car was to go fast with class i.e. a Corvette, I hope you can do the same with your GSX.


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Old 01-24-2003, 09:16 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #5 (permalink)
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Exhaust is more of a multiplier than a hp adder. When I added my downpipe and test pipe I did gain almost an entire second off my 1/4mile. While it might add 10-20 hp to a T-25, the difference would be much greater if you were running stock exhaust with a 16G. Like cucumber says go with new exhaust. A test pipe will help but you will be a lot louder.

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Old 07-10-2003, 12:43 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #6 (permalink)
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yeah alot louder...my car sounds like and 18 wheeler... i would say 20hp maybe fly wheel...no way 20 rwhp....

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Old 07-10-2003, 02:56 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #7 (permalink)
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We had a customer come in with a 91 GSX. We added a catback, testpipe, boost controller, and an ACT clutch. He ran 13.7@99 on pump gas.

Not bad.

Exhausts do help a lot on turbo cars.
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Old 07-10-2003, 03:31 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #8 (permalink)
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Quote:
Originally posted by prostreetonline
We had a customer come in with a 91 GSX. We added a catback, testpipe, boost controller, and an ACT clutch. He ran 13.7@99 on pump gas.

Not bad.

Exhausts do help a lot on turbo cars.
what size was the catback and testpipe? 2.5" or 3"?

also with the boost controller what was the boost set at?

is that all the mods he had on his car or were there more , and if so, what were they?

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Old 07-10-2003, 03:35 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #9 (permalink)
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Quote:
Originally posted by Prodigy
no way 20 rwhp....
Well, ya. Since no dsm's are rwd then ya thats impossible.
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Old 07-10-2003, 04:38 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #10 (permalink)
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Quote:
Originally posted by XxXEcLiPsE93


what size was the catback and testpipe? 2.5" or 3"?

also with the boost controller what was the boost set at?

is that all the mods he had on his car or were there more , and if so, what were they?
2.5" Testpipe, 3" A'PEXi N1 catback, boost was around 19psi.

No more power mods, just ACT Clutch.
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Old 07-10-2003, 07:34 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #11 (permalink)
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i was told that removing the exaust on a stock car gains 40 h/p but thats just what i was told, dont quote me on it.

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Old 07-10-2003, 07:49 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #12 (permalink)
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Re: how much hp does a catback exhaust system add?


Quote:
Originally posted by c5chris
im not a believer in exhaust systems other than it's just all sound and no added hp - well maybe 2-5 hp tops. i rather add headers and do something before the cats than add something after it. but thats for my other car. for the dsm say, i add a greddy catback or an rsr catback, how much power will i add? i want to hear from people who added them and dynoed to prove it.

Either NA or TC'd the gains of the exhuast depend on the other parts of the car.

Breathe in Breathe out. If it's having trouble breathing out because the exhaust is stock but the turbo was swapped and it was cammed or something. You will gain alot. If something is choking the intake side or you don't have enough fuel for the amount of air you can flow now you wont get much.

The only major point of restriction on a turbo car should be between the exhuast ports and the turbo. From the turbo gradually expand from the turbine exducer diameter to the diameter of exhaust that matches the power level you are looking to produce.

NA cars typically run best with equal length headers that have primary and collector tube sizes matched for the power band the intake and cams are setup for.
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Old 07-11-2003, 03:12 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #13 (permalink)
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[QUOTE]Originally posted by Slappster


Well, ya. Since no dsm's are rwd then ya thats impossible.
[/QUOTE


Well thanks Smart ass..... I learn something new...
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Old 07-11-2003, 06:21 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #14 (permalink)
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A typical cat-back adds about 5 hp and they cost an insane 500 bucks or more depending on what you get. NOW, like somebody said before they are a horsepower multiplier in that you need a free flowing exhuast to extract the horsepower from other modifications. I suggest getting not only a cat-back, but also getting a dp. A full 3in system multiplies HP quite a bit. Getting rid of the cat or getting a high flow cat is a huge advantage over the stock system. In fact, if you have an old cat it may be clogged. In one of my turbo books, I have read where a clogged cat can take away 10% hp. However, if you get a full 3in DP with no cat like I did you will run into the problem of boost creep. In order to get rid of that problem you either need an external wastegate or port the hell out of your O2 housing and turbine housing and get a 34mm WG valve. Even that doesn't stop boost creep in the winter. But, now that it is summer, I get rock steady boost. On top of adding hp, free exhuasts relieve back pressure (dur) and allow almost all of the gases to escape the cylinder during the exhuast stroke. This lowers cylinder temps and lowers the chance of detonation. Thus, it gives you more leeway when tuning. Exhaust systems also add style and sound to your car. I have a full Apexi N1 system and absolutely love it. It sounds top notch! Free flowing exhausts are key to extract HP from turbo cars.


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Old 07-11-2003, 06:29 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #15 (permalink)
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Re: Re: how much hp does a catback exhaust system add?


Quote:
Originally posted by MNGSX



Either NA or TC'd the gains of the exhuast depend on the other parts of the car.

Breathe in Breathe out. If it's having trouble breathing out because the exhaust is stock but the turbo was swapped and it was cammed or something. You will gain alot. If something is choking the intake side or you don't have enough fuel for the amount of air you can flow now you wont get much.

The only major point of restriction on a turbo car should be between the exhuast ports and the turbo. From the turbo gradually expand from the turbine exducer diameter to the diameter of exhaust that matches the power level you are looking to produce.

NA cars typically run best with equal length headers that have primary and collector tube sizes matched for the power band the intake and cams are setup for.


Well the great thing abt N/A mods is that sometimes the parts stack in HP, increasing 1 part is not enough, but increasing many parts make them all more HP since they are increasing free flowing airflow. so you will need downpipes, free flowing cats and such... Its never just an exhuast. its an "exhuast system" System being key word, you change 1 link little is done you change the whole then everything is done.

P.S. well they also have other functions too, like take intakes for example, they help spool ## turbo up faster but they also dont add that much HP... And i believe exhuasts are supposed to release backpressure?


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Old 08-04-2003, 12:46 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #16 (permalink)
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Think cops would care if you took of the cat? I mean I know its illegal in most if not all states... but would they care / know?
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Old 08-04-2003, 04:15 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #17 (permalink)
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What do you mean if the cops won't care? If they find out you don't have a cat on the car they probably will give you a hefty fine and possibly impound your car/suspend your license depending on your area. But then again it all depends on the cop....
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Old 08-25-2003, 01:57 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #18 (permalink)
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Does anyone know some solid figures about how much performance you can extract out of a 2.5" mandrel-bent turbo-back system with cat? In terms of track times and HP?

Actually I plan on getting 3" press-bent turbo-back w/3" cat. Reason for 3" press-bent, so I can use the 3" cat with 3" inlet and outlet, opposed to only 2.5" inch inlet/outlet on cat. And it stays _approximately_ equal to 2.5" mandrel in terms of flow.


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Old 08-25-2003, 03:32 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #19 (permalink)
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Quote:
Originally posted by prostreetonline


2.5" Testpipe, 3" A'PEXi N1 catback, boost was around 19psi.

No more power mods, just ACT Clutch.
No other power mods huh? So he was running 19psi on the stock injectors, fuel pump, and wiring? Thats smart


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Old 08-25-2003, 05:14 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #20 (permalink)
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Quote:
Originally posted by 91TSi FWD


No other power mods huh? So he was running 19psi on the stock injectors, fuel pump, and wiring? Thats smart
Yep... his car happened to be one of those "super rich" from the factory cars, so he was fine.
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