Mixed Exhaust Signals...

Dauber

Registered User
Ok.. here is the deal.. I own a 1991 Supercoupe. I have been searching through past threads and what not.. and have been getting mixed signals as to what I should do for exhaust. I first checked the FAQ section and basically learned that more flow is good. But the "Thank You Capt. Obvious" answer wasn't quite what I was looking for. ;)

I found there is a flowmaster setup that has a 2.25" center section. To me.. that just doesn't sound that impressive. 2.25" cat-back is a mild upgrade for a Cavalier...

What exactly is the optimal setup in sizes/arrangement for the supercoupe? Go with cats, no cats, or highflow cats? Remove the resonator, go with a magnaflow or flowmaster resonator? Should I run dual 2.25" into a 3" center section, and then back into a dual 2.25"? I read that I can't go with a true dual setup because of the fuel tank on my 1991. At this point and time.. the fuel tank swap isn't an option. Maybe later on down the road when I have to drop the tank anyways for new pump.

Whatever the case may be.. I would like the most optimal setup for performance.. allowing room to grow with motor performance.. ie.. more boost. I'll probably end up going custom at a local shop.. but the mufflers and resonator to use would be helpful. I would like to have an exhaust that sounds just as good as it performs.
 
exhaust

on my 90 SC i went with 2 1/4" downtubes with high flow cats, replaced the resonator with basically a flowmaster clone, with dual 2 1/4 inlets and a single 3" outlet, then split back into dual 2 1/4" tailpipes with Dynomax turbo mufflers. I noticed better acceleration and it sounds awesome under full throttle, not loud at all just healthy. My only problem is at normal acceleration it's just 2 damn loud, and kinda reverberates thru the car, also does this at about 70 on the freeway in overdrive (at 80 it's fine! )
Anyway i got an "XLerator" muffler to replace the flowmaster clone, it's 4 inches longer and has some packing in it to mellow out the sound, but still is basically a straight thru design, so as soon as i can get my buddy who has the lift and the welder to help me with it, we'll see if it improves the sound !
 
Yeah... that is sort of the setup I had in the back of my head. I was thinkin of using CATCO highflow cats, 2.25" into 3", then back into 2.25." Right now I'm stuck on mufflers...

What kind of tone do those dynomax put out? Is there another vehicle you could compare it to? I dunno.
 
I guess it depends on how far you want to take your car. The exhaust setup that you are thinking about is good to around 275~ rwhp, maybe more. But is still somewhat restrictive. Not all that bad, though. Don't get me wrong. Here is what I plan on doing, keep in mind though, I'm going all out eventually (check out my signature :) )

Coy Miller Stage I Headers (Short)
1 3/4 primaries with 2 1/2 collectors 2000* coated
2 1/2 down tubes to
2 1/2 high flow cats
X-pipe with remaining exhaust being true dual 2 1/2s
Haven't decided on the mufflers yet.

And Yes, I have an '89 so I am getting the new style tank and upgrading to the 255 lph fuel pump at the same time. Not the cheapest route by any means, but I think that it will perform quite well. I'm setting the exhaust up for a Coy Miller Race Engine that will eventually grace my engine compartment. In the meantime, I just want some free flowing exhaust. I know that I will loose some low end torque with this setup, but I plan on getting it back with mods.

And if you notice, from the collectors back, it will all be 2 1/2". This is done to reduce exhaust restriction. Everytime there is a change in the diameter of the exhaust piping, there is turbulence. Turbulence equals back pressure. That will help keep the exhaust velocity at more of a constant speed. I'm pretty sure this setup will support upwards of 400 rwhp. This is just what I have found through my exhaust searches (not just here on this site). Hope it helps you decide on a course of action. My .02 would be to go ahead and change the tank to the newer style with an upgraded fuel pump. Then it's done and you won't have to worry about it. You can find plenty of newer style tanks a junk yards. I'd go to a parts store or even Ford for the straps though. Anyway, that is just my .02.
 
I just had Flo~Pro muffles installed and they sound awesome. No resonator (replaced it with a y pipe). Futures plans to run down tubes to hi-flo cats
 
90 Cat

On my 90 cat I have custom 2.5 inch down tubes with no cats, into a y pipe, the into a 3 inch center section, no res, back 2.5 and out to Dyno Max Super Turbo's. At idle the car sounds great, when you get on the throttle it is a little raspy, but afer about 2500 RPM all i can hear is bower:D
 
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