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Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 08-26-2005, 01:13 PM   #1
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I have a 2002 SE Bonneville. Looking a doing an exhaust mod. I was given a muffler with a 3" inlet/outlet. Do you think I would be better of going with a complete exhaust with 2.5" piping, adding a high-flow catand muffler to my existing piping, or just putting on the muffler that was given to me? Got an estimate for high flow cat and 40series flowmaster added to my existing piping for $300.
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Old 08-26-2005, 01:13 PM   #2
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current mods intense standard pcm and custom CAI
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Old 08-26-2005, 02:04 PM   #3
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Most of the quickest cars here are running stock mufflers, and only run a high-flow cat. 8-ball, the second quickest Bonneville, is the same.
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Old 08-26-2005, 02:43 PM   #4
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Quote:
Originally Posted by willwren
Most of the quickest cars here are running stock mufflers, and only run a high-flow cat. 8-ball, the second quickest Bonneville, is the same.
Actually, 8-ball also has a set of SLP headers but your point is very well taken.
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Old 08-27-2005, 02:45 AM   #5
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you dont want big piping...........2.5" is to big for a near stock 3800. id go with 2.25", 2.5" if you have a supercharger.

as far as performance goes, you want a smaller pipe with strait through mufflers. its finding the best combination. your pipes aren't what are giving you your back pressure, you mufflers are. which is why on a near stock or bolt on car, keeping the stock piping and upgrading the mufflers/cats is your best idea. you can tune the sound with resonators/glasspacks

ricer theory tells you you need huge piping, and the biggest cone filter for a cai. both of which will hurt your performance.
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Old 08-27-2005, 03:39 AM   #6
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My car has stock 2.5".... I also was 1/2 a second faster in the 1/4 mile compared to a car with the OE muffler mine used to have. 1993 does have better tires, but his intake is a lil different too.

Rogue has a high flow cat as well as the SLP'*. Just because he'* the fastest with stock mufflers, doesn't mean he wouldn't be faster, only would know though untill you tested both.
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Old 08-27-2005, 03:40 AM   #7
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Quote:
Originally Posted by mikey
you dont want big piping...........2.5" is to big for a near stock 3800. id go with 2.25", 2.5" if you have a supercharger.

as far as performance goes, you want a smaller pipe with strait through mufflers. its finding the best combination. your pipes aren't what are giving you your back pressure, you mufflers are. which is why on a near stock or bolt on car, keeping the stock piping and upgrading the mufflers/cats is your best idea. you can tune the sound with resonators/glasspacks

ricer theory tells you you need huge piping, and the biggest cone filter for a cai. both of which will hurt your performance.

I agree with most of your statement. Big piping on a stock bonnie is a no no, I have stock piping and a flowmaster 40 and am quite happy with the performance.

What I don't agree with is half of your "ricer theory" I believe you need more surface area for the air filter. Reason being is the more surface area the more air you take in.
The material the filter is made of has a lot to do with it, cotten gauze vs. paper.

But the size of the surface area matters also.

Peace,

Tim
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Old 08-27-2005, 03:49 AM   #8
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Thanks for the information. I'll stick to plan A and get the high flow cat and flowmaster. Wife has already approved. So I shouldn't change plans now anyways.

Next question. pems vs. headers? any good comparisons done?
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Old 08-27-2005, 03:51 AM   #9
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You need the best CFM for your motor really. ALL back pressure is bad, larger pipe doesn't give backpressure, it just slows it down like a traffic jam at lower speeds, hurting things like exhaust scavenging.

Our piping is semi restrictive. It makes a good number of turns, probably atleast 270* worth of them, it not more. A straighter design with mufflers running longitudal would give better flow, and it is possible, someone fabbed one up about 6 months ago. It just takes some work.
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Old 08-27-2005, 10:37 AM   #10
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BonneMeMN is right. Velocity is just as important as backpressure.
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