Hi.

I was wondering how many horsepower I will gain from installing a high-flow cat and complete exhaust with flowmaster muffler. Anyone have an idea?

Thanks,

Dan

Not as much as you want. Maybe 10 on a good day.

Unless the cat is really shot. I gained 3 second in the quater mile just by changing the cat....

Granted it had blownup and lodge a big chunk in the exh. pipe.

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85 GT 4 SPD
Number 53715 of 76371
Best 1/4 15.816 @ 84.72

Accel 8.8mm wires, Accel 300+ Ignition box, Blaster Coil, NGK UR5, K&N, Short Shifter, High flow cat, Monochrome Caracus red, KYB shocks/struts, ST lowering springs, Poly Dogbone.

Coulee Region Fieros member(couleefiero.tripod.com)

I built an exhaust for a friend's '86 GT. It was a new cat, 2.5" mandrel bent tubing, into a West Coast Fiero modified Flowmaster.

We dyno'd the car before and after, and the new exhaust lost about 2hp across the board over the stock exhaust.

I blame the muffler. I was quite unimpressed with the design and workmanship of WCF's modifications.

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Doug Chase
'88 Fiero Formula 5-spd (autocrosser)
'88 Fiero GT 5-spd (daily driver)
'85 Fiero GT 5-spd (rally car)
'87 Fiero SE V6 5-spd (for sale $2200)
'88 Fiero Formula 5-spd (parts car / future rally car #2)
Custom roll cage fabrication available
Custom exhaust fabrication available

Edited because I left out some important details

[This message has been edited by Doug Chase (edited 04-23-2003).]

quote Originally posted by Doug Chase: I built an exhaust for a friend's '86 GT. It was a new cat, 2.5" mandrel bent tubing, into a West Coast Fiero modified Flowmaster. We dyno'd the car before and after, and the new exhaust lost about 2hp across the board over the stock exhaust. I blame the muffler. I was quite unimpressed with the design and workmanship of WCF's modifications.

Interesting, I would blame the restriction of a new cat, oh well - my 0.02 cents

I've already put a high flow cat in it, but only because the old was was garbage, it wouldn't let the engine rev over 3000rpm, and it would hardly accelerate. I think there was an improvement, but its hard to tell becuase the cat has been bad for a while, it definately sounds better. The tubing is rusted in a few spots, so I was thinking I should replace the whole deal. I guess I'll stay away from the modified one, and go with the stock flowmaster if I do it. Would a new air intake help? The 2.8 seems to be hard to squeeze power out of eh?

Thanks for the help,

Dan

quote Originally posted by West Coast Fiero: Interesting, I would blame the restriction of a new cat, oh well - my 0.02 cents

It's hard to say. We changed three things at once (cat, pipe, and muffler) so it's really impossible to say which one in particular caused the problem. If I had more money and time I'd test all the parts seperately and find out for sure.

Have you guys dyno tested this muffler, and if so, what did you find?

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Doug Chase
'88 Fiero Formula 5-spd (autocrosser)
'88 Fiero GT 5-spd (daily driver)
'85 Fiero GT 5-spd (rally car)
'87 Fiero SE V6 5-spd (for sale $2200)
'88 Fiero Formula 5-spd (parts car / future rally car #2)
Custom roll cage fabrication available
Custom exhaust fabrication available

I too am not impressed with that particular muffler and plan to get rid of it in favor of an 80 series once I install my '88 cradle. One thing you notice after a while is that the exhuast flow from the two tips aren't even close to equal. On cold mornings water vapor only rises from one side of the car and after a couple hundred miles of driving the passenger side tips are nearly free of soot while the drivers side look like they haven't been cleaned in months. This would seem to be a restriction to forcing most of the exhuast through a 1 5/8" pipe. On the other hand it sounds great.

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Alan Frazier
'86 GT-'92 3.4 TDC under construction
'84 2m4 daily driver

I'm not sure just how WCF mods them, but I do know Flowmasters are designed to work with an exact path of flow throgh them. It would make perfect sense to me if you changed that, they would not perform anything like they were made to. Sounds kind of bass ackwards to try to modify something like that. But like I said, I have not seen one of those.

Whats the difference between the 40 & 80 series? Will either work on the stock fiero?

Thanks again

Not enough to spend the money on it... in my opinion at least.

Keep in mind you have to worry about taking torque away as well and the fiero's fairly high torque makes it fun to play with

just bore out your cat, save your money, and get great sound and performance.

Klax,

I already have a high flow cat. I would have gone without one, but I still need to pass an e-test, would boring the cat screw that up? I think I'm going to go with the flowmaster