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Straight piping the exhaust?


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9 replies to this topic

#1 Surfdougyfresh

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Posted 22 September 2004 - 11:01 PM

Hey everyone! My '98 OBW with 2.5 is running fine, though I have to wonder how much additional power I can gain by removing the cat and straight piping through maybe one can, rather than what exists now. I'm living in Saudi Arabia where emissions are talked about, but it's little more than lip service , so that's not an issue. What about retaining engine performance? Will removing the back pressure cause the engine to run any rougher/louder than it already does? Has anyone tried this? What about exhaust note?

#2 LosDiosDeVerde86

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Posted 23 September 2004 - 12:12 AM

Hey everyone! My '98 OBW with 2.5 is running fine, though I have to wonder how much additional power I can gain by removing the cat and straight piping through maybe one can, rather than what exists now. I'm living in Saudi Arabia where emissions are talked about, but it's little more than lip service , so that's not an issue. What about retaining engine performance? Will removing the back pressure cause the engine to run any rougher/louder than it already does? Has anyone tried this? What about exhaust note?


it will definiatly be louder and throatier...possibly. it all really depends on the car. with some cars, if you remove the cat, they sound mean and beefy. other, on the other hand, sound like a lawn mower.

#3 Setright

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Posted 23 September 2004 - 12:31 AM

Cats tend quell any snarl and "barp" noises. More of these is a GOOD thing!

Please make a good recording for us all to hear :-)

#4 ScoobySchmitty

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Posted 23 September 2004 - 08:51 AM

DO IT!!! If you can, get a beefier exhaust manifold too. I don't believe back pressure affects performance too much, so give it a shot, but keep your old system around just in case.

#5 coloradosubarules

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Posted 23 September 2004 - 09:43 AM

While you are under there find out ho many cats there are. I was looking under my Roo and notice 3 large items. cat, res, muffler? I am contemplating doing away with the cat but I want to know what I am getting into before I do. You pretty much have to pull the entire exhaust off just to delete te cat.

If you end up doing it please keep us updated.

#6 Setright

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Posted 23 September 2004 - 10:06 AM

Colorado, the cat is the first expansion. The second thing is a resonator designed to boost torque by sending pressure pulses back along the system. The idea is for the pulse to encourage the exhaust gases to leave the the combustion chamber. The final thing is the actual silencer.

At least it was like that on my 1990 BC7.

#7 LosDiosDeVerde86

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Posted 23 September 2004 - 02:36 PM

less back pressure is good, more flow. but, however, no back pressure is a bad thing. it's a sensitive item.

#8 MorganM

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Posted 23 September 2004 - 05:49 PM

One thing to consider is your O2 sensors. I belive you have 2; one before and one after the cat. ? Youll want to get 2 bungs welded in so you can screw in the O2 sensors. Otherwise your Check Engine Light will be on 24/7 and your gas milage will drop.

ALso if you are nuking the cat you better chop out all that other crap and put on a higher flow muffler or really you aren't doing much.

#9 99obw

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Posted 23 September 2004 - 06:16 PM

You will have to fool the computer to keep the MIL off, as the computer is expecting a difference in O2 concentration before and after the cat.

#10 coloradosubarules

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Posted 23 September 2004 - 09:30 PM

I was just going to gut the cat or replace it with a deletion pipe. I will most likely leave the rest of it alone. Although my wife can't stand the rattle of the exhaust sheilds so maybe I will do some more mods. Maybe a custom res and a sweet flowmaster? OR skip the Res and go straight to a flowmaster. Hmmm...

Anybody know if they list a flowmaster for this car? Or univeral?

What is the SAE size of the pipe?




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