I am considering purchasing a test pipe (straight pipe) to replace my stock cat. I am also going to replace the stock exhaust with a Greddy SP. I do have a short ram on my intake. What will be the effect of the reduced backpressure? Also, is there a realistic possibility of permanent engine damage?
Thanks.

 

Isn't it when you reduce backpressure you lose low end torque but gain high end horsepower?

 

I'm asking the questions here buddy.

 

If you remove your cat, you will pick up only about 5-10 HP. However, the harmful emissions released will increase about twentyfold ! In most states, you will get a pretty serious ticket or fine if and when you caught without it. (Some states will even confiscate your car making it an expensive, time-consuming pain in the ass to get back !) And you can expect your "Check Engine" light to remain on constantly as the unplugged sensor tells your ECU that yout cat is malfunctioning.

Still think it's a good idea ?

 

why only 5-10hp? I took out the resonator on my HKS (axelback exhaust!! psshh) and replaced it with pipe, and i think i lost some low end torque... but, when i pull into 2nd gear, my tires SCREACH!! *errrghh* on the smooth pavement. so i think i gained some high end HP.

 

back in '94 out here in Cali, the fine for not having a cat was 3 grand. And back then, almost every street racer had their cat out and you could hear the cars a mile away, enough so that 5-0 was targeting these cars. I know a lot of people who got busted (at late night street racing or by CHP on the freeway where cat-less cars were at their loudest.

It got so bad that a year later, everyone was putting their cats back in.....

 

great story..

 

if you do alot of city cruising then a cat/exhaust will probably be all fo show and no go. since u loose low end torque like when your taking off. but if your simply getting it for the looks and for passing people/highway driving then good. choice.

As for engine damage. hmm hard to say. I heard that adding an aftermarket exhaust helps because it lets the exhuast out of the engine bay eaiser. could be BS tho

 

You do the math: 1" reduction in back pressure can equal about 1 HP gained. The pressure drop across our catalytic converter is about 1" - 1.5" per 100 SCFM. How much SCFM do our cars flow, not more than 500 for sure, more like around 400 max!

The above is outside of the emissions issues. The HO2S2 (2nd O2 sensors) is mounted in the cat, removing it will set a DTC and illuminate the SES light. There are devices out there to simulate this signal so that the PCM thinks everything is OK. Then you have to worry about your region if visual inspections are made or if even emissions testing is done. If either is the case there is no choice but not to do it.

 

Thanks, is there a realistic possibility of causing permanent engine damage?

 

No, there really is no real reason that damage would occur.

 

I think we should leave this subject on that note.

Phin, it's bad to take out your Cat :P