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post #1 of 7 (permalink) Old 10-14-2003, 12:28 AM Thread Starter
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How much exhaust back pressure?

Does anyone know how much back pressure a 3.5L is supposed to have. Also, if you have done an exhaust mod that included taking out both stock mufflers and/or cat. converter please send me an e-mail at [email protected] with your experience (Do you like it, how it effect your performance, what you did, what kind of muffler, etc. Use a subject like "EXHAUST MOD" or something so I don't think it is junk mail. Thanks for your help!!
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post #2 of 7 (permalink) Old 10-14-2003, 06:11 PM
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Check your email, just sent you a little somthin'.
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post #3 of 7 (permalink) Old 10-15-2003, 01:00 AM Thread Starter
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I have gutted my cat. and am just using it as a Y pipe. I plan (or want to) Y off of the 2.5" pipe that leads in to the main (square) muffler and make dual exhaust with Flowmaster Delta 40's (same as "argus" but I think this cat. is still working). So pretty much the only thing that would be on the exhaust is stright pipe and two FM mufflers. Would this be enough or is there something I could put before the mufflers to create more back pressure. Would going with single exhaust add enough backpressure to just go single. I know my way around cars a little bit but exhaust work isn't my speciality, so I am going to need some help with knowing what I need to do to get both sound and performance. I can't go ask the exhaust place I am going to about making up backpressure because of a gutted cat. or they wount be able to even work on any part of my exhaust. Anyone with idea's, help, or anything please email me at [email protected].... And thanks again "rce2win".
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post #4 of 7 (permalink) Old 10-15-2003, 07:45 PM
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I like to do exhaust mod, perhaps dual exhaust to improve the tail-end's look and performance, but don't like the noise that the most performance muffler makes (Flowmaster 40, which is what my Villager has). Do you think the dual exhaust in this case will prove, with the catalytic converter in place ?

My 2000 ES is a 3.2L, no mods.
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post #5 of 7 (permalink) Old 10-16-2003, 12:42 AM
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i wouldnt mess much with the flow of the system. Youll gain a peak at the systems tuned frequency vs RPM. The stock system is setup to be quiet and produce nice low down torque to increase drivability.

Im not saying that its not possible to gain power across the entire curve as the system maybe overly restricted, but at the same time if the system is not properly designed you can lose power.

If youd like to design a exhaust system i recommend getting into a software pakage like ricardo...but thats extremely complicated but is also extremely complicated.

youre on the right track with the idea of backpressure. Backpressure means torque....and torque means HP
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post #6 of 7 (permalink) Old 10-16-2003, 01:19 AM
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It seem that dragsters have just header pipes (no mufflers, collector, or cats). and they have plenty of HP. If back pressure means HP and torque then we should just plug up the pipes. LOL I tend to go with the lower (restriction) the better.
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post #7 of 7 (permalink) Old 10-16-2003, 04:00 PM
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dragsters run for about a minute from start to finish then they go through the engine.

Not having any back pressure is hard on the exhaust valves and will lead to their very earlier failure. So free flowing is not the best thing in the world....except in turbo apps where the turbo presents back pressure...but after the turbo you want to get that stuff out of there as fast as possible.

Making torque down low is about flowing air down low...which means back pressure...among other things such as intake design and small valves. What our cars have from the factory is a balance of down low torque and high end power. A nice balance if you will. Not that uncorkying it some wont sure it will...but too much will remove power from under the curve.

when you go to make the system try to make it flow more....but not to well. There is a balance....

I am in a FSAE team in which we build a 600lb race car that pulls 1.5 lateral gs and goes 0-60 in 3.6 secs. See current issure of road and track. Last year we had the fastest car out of everyone hence our feature in the magazine. We had ~75hp while other teams had 90hp. Our car was still faster...why? not becuase of weight...becuase we had torque while the other teams had a peaky power curve. Sure they peaked at 90hp...but made a lot less on average than our engine did.

Its not about peak power...its about usable power.

and as far as dragsters go...when do they spend anytime at lower RPMs? Dragsters and a street car, or track car are very very different.

here is a interesting device
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