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Old 10-11-2003, 02:00 PM   #1
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Default straight pipe no cat

hello everyone, would running with a straight pipe and no cat affect performance ?
does it throw off the ecm or anything. The reason I ask is that the pipe on the cat convertor is cracked and my local muffler shop said it would be okay .I did it because I'm a little short on cash right now. Oh by the way I'm referring to my winter beater, a delta royale 1989.
thanks in advance for any input.
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Old 10-11-2003, 03:10 PM   #2
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I'd be tempted to keep a Cat for the backpressure, but go with a hi-flow design. You don't have the extra O2 sensor after the Cat on either car, so the lack of a Cat wouldn't affect the PCM at all, but it'* still best to keep it unless you're building for pure performance.

You can get a performance Cat for the $100 range, plus installation if you don't do it yourself. You may feel the difference in performance, especially if the old cat is clogged or even leaking. These things are tuned for a specific amount of backpressure. Too much or too little will both hurt performance, but in different ways.

If you lose too much backpressure, you'll lose low-end torque, and that'* what these engines are known/built for.
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Old 10-11-2003, 04:01 PM   #3
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I don't recommend a cat-less car either, I second the bossman, high flow is the way to go, and it creates a nicer sound as well
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Old 10-11-2003, 04:19 PM   #4
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gordy put your .02 in here...keep the cat the low end torque is awesome!
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Old 10-11-2003, 09:07 PM   #5
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What if you have a SC? I know with my Turbo car the less backpressure the better. Does the same apply to a SC?
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Old 10-11-2003, 09:10 PM   #6
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I believe it applies even more to have backpressure when you have an SC
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Old 10-11-2003, 09:11 PM   #7
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So what kind of upgrades can you do on the exhaust side that will actually increase the performance?
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Old 10-11-2003, 09:15 PM   #8
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High flow cat, 2"-1/4" or 2.5" pipe and a nice muffler, either Flowmaster or MagnaFlow, or you can go as far as porting the manifolds and some serious engine mods. It all depends on your budget
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Old 10-11-2003, 09:21 PM   #9
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So then things to decrees resitance but still maintain back pressure. No after market manifold? What kind of hp increase is possible on the exhasut side if I didn't want to get into interanls? Same on the intake side? I've already seen debate about the airbox. I've encountered similar issues with my Conquest.
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Old 10-11-2003, 09:50 PM   #10
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The key to remember is resistance without being restrictive. A high flow cat will add necessary resistance yet open up the flow a bit. It will add a nice 5-10 HP boost and add a more agressive sound.

Mandreal bends in your pipe is a nice expensive alternative that allows for nice out flow. A muffler option again adds performance due to internal design.
Any stock exhaust is WAY to restrictive, you'll notice a nice increase. The muffler should add another 10HP to the system. What you choose to do with the resonator, its up to you.

As for the intake, some gut, some go intake pipe and filter or rig up a true CAI intake system. Remember, do them at the same time, or do the exhaust first, doing an intake first and ignoring the exhaust is not going to help
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