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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 07-07-2007, 11:04 AM   #11
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I will ask Ryan, my tuner, about this. He normally messes with Fieros and that may be a different situation compared with a FWD application such as a Reatta
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Old 07-07-2007, 11:20 AM   #12
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Frankly, you should ask the people here who have far more experience in exhaust on the 3800 FWD'*.

You will lose exhaust velocity HORRIBLY. We have a 94 SSEi on the Forum right now with 3" exhaust running 2 full seconds slower than he should.

Another 95 SSEi did this 3 years ago and lost his low-end torque.

INTENSE dyno'* more cars than any other performance company PERIOD. And on the Bonneville to-25 list, only a very small portion of the cars are running 3". Those cars are all running quicker than 13.5 on the quarter.

You won't be anywhere close to the power they produce with ported heads and SC. In fact, you'll probably be short of my 93 as well, and I still have 2.5 exhaust. I can also kill my low-end torque by opening my cutout for the launch. I leave it closed, and open it during the run now so that it'* free-flowing at the top end, not the bottom.
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Old 07-07-2007, 04:43 PM   #13
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I think what you mean is you want a 3" downpipe. Like everyone says full 3" would kill your torque. I think a 3" downpipe, PEMs or headers, rockers, and a 3.25" pulley would be a killer combo for that car.
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Old 07-07-2007, 06:10 PM   #14
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But NOT a 3" downpipe with the simple mods he listed.
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Old 07-07-2007, 07:46 PM   #15
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Quote:
Originally Posted by willwren
But NOT a 3" downpipe with the simple mods he listed.
Pay attention to willwren!!!

There is A LOT more going on than "Bigger pipe - Less restriction"!

The exhaust system is dealing with pressure pulses, inertia, and velocity (and other things as well). To oversimplify, a 3 inch pipe has WAY TOO MUCH volume for optimum velocity. The inertia of the pressure pulse and its associated low pressure that follows is ONE of the things that assists in EXTRACTING the exhaust out of the cylinders.

This is a DYNAMIC system and can therefore be COUNTER intuitive. You want to set up a pressure pulse moving down the exhaust pipe at high velocity and proper timing with the rest of the system. It is very similar to an acoustic system where the porting and volume are defined specifically for a frequency.

It isn't as simple as you think!

Listen to willwren. He not only knows from other people'* experience, he'* probably tried almost everything himself.
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Old 07-08-2007, 10:20 AM   #16
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Should the system be 2.5''?
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Old 07-08-2007, 12:22 PM   #17
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Cat-back, yes. You still need to address the manifolds though. Get PEM'* or headers and a high flow cat.
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Old 07-08-2007, 12:28 PM   #18
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Quote:
Originally Posted by dillcc
Cat-back, yes. You still need to address the manifolds though. Get PEM'* or headers and a high flow cat.
I'd have to disagree. He'* not talking about any power-adding mods. Ported heads and SC don't dictate much downstream.

If he were talking valvetrain changes, then sure.
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Old 07-08-2007, 12:37 PM   #19
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Hmm, what'* the stock exhaust, 2'' probably? 2.5''? And it sounds like my stock muffler should be able to handle the flow
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Old 07-08-2007, 12:44 PM   #20
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We have no idea what your stock exhaust was/is.

We can tell you that MOST early 90'* 3800 non-supercharged were 2.25".
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