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Old 03-17-2012, 06:06 PM
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BigRedOne BigRedOne is offline
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Jury's in: I don't think it was the cat's. As it stands with the 37's it runs best when I keep it ~ 2000rpm. Much lower and it labors to accelerate in 4th and 5th.

I ended up w/ magnaflow cat's (P/N 39006) and a double-in, single-out magnaflow big block muffler w/ a 3" madrel-bent exit pipe routed over the axle, behind the pass-side rear tire. I don't want the hassles that come with headers so I stuck w/ the OEM 2.25" pipes to the cats. The cats themselves are 2.5" in & out. My butt dyno says maybe 5% gain, maybe, but there is a noticeable gain in throttle response and torque coming off idle, making it easier on the clutch coming off a stop, but harder on the tires Note: Here in California we are forced to run catís or I wouldíve ditched them long ago. Engine note is throaty but barely louder than stock and most importantly, no drone!

Re: rpmís Ė Iím hitting 50mph at 1600rpm and at 65mph Iím turning 1900rpm in 5th gear. My spedo is reading 55mph when I'm actually doing 65mph so when I think back to how it ran before I think it's just a matter of running out of hp necessary to overcome the added wind drag of the higher profile stance, plus overcoming the increased mass & inertia of the bigger tires.

Iím hoping my fastman throttle body and cold air intake will make good use of these exhaust modís to give me more muscle to turn these tires. Iíll likely post a new thread summarizing the combined results when I finish the whole setup.
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