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Thread: Hi Flow cat

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    Hi Flow cat

    Question for all you experts!! My 02 is stock, I was wondering if I added a true hi-flow cat would I see any differance in performance/gas milage? If so are what is a good one to get? Thanks for your help.

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    I put high flow cats and midpipes on mine last week, but for some reason it seems to me like mileage has gone down, as well as performance. My girl even said it seems slower now. I don't know how that's possible, maybe the pipes didn't get tightened up right, and I've got a leak somewhere? USAF150H-D, don't take my case as the norm, I'm sure I'm like a one in a million case.

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    Anyone else offer any insight to this question? I know mine wasn't helpful at all lol (plus I'd like to know if anyone has an explanation for my deal lol)

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    if you add highflows to a stock truck - you wont notice much of a difference in performance - just noise - more noise, same scoot - but it doesnt seem as quick because you lost some low end torque but gained upper rpm hp - im sure youd notice a difference if you punched it going 60 mph to pass someone. the factory exhaust system in these trucks (the 02-03) is very adequate up to around 400 hp - which is when boost levels are a lot higher and the air needs somewhere to go.

    hope this helps

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    Originally posted by 4CFED
    the factory exhaust system in these trucks (the 02-03) is very adequate up to around 400 hp - which is when boost levels are a lot higher and the air needs somewhere to go.
    Yup, close... it was about 550 hp when I started seeing diminishing returns on mods. I'm still running stock headers, cats, but Bassani cat-back.

    I tend to believe that high-flow cats are probably the best bang for the buck when it comes to exhaust mods.

    AFGuy0127, did your boost drop? Do you have a gauge hooked up? I would think that you're flowing more air now, probably making more power but doesn't seem as eventful as before. The butt-o-meter is quite inadequate for judging power... this is a long shot, but I would clear your computer and let it remap the fuel curves as increased air flow could affect you - though I've often heard leaner. Perhaps you are running richer, which quenches power and is bad for mileage.
    2002 Black Harley-Davidson F150
    2.6 KB, DMP Built Motor, Dynatech LT's

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