How Much Horsepower Would I Gain Cutting Off The Cat Converters And Putting On A Flowmaster

Posted in Exhaust and Mufflers | Asked on May 21, 2010

My 3.0 liter ford enginge is being rebuilt right now and i am debating on wether or not to cut off the catylitic converters or leaving them. And i already ordered the flowmaster exhaust. So how much of a gain should i expect? ((O almost forgot! With cold air intake Maybe????))

There are 8 Answers for "How Much Horsepower Would I Gain Cutting Off The Cat Converters And Putting On A Flowmaster"

  1. JetDoc says:

    Probably not much. Modern engines are tuned to run with the back pressure that catalytic converters create. If you remove it, your fuel mileage and engine performance may suffer. If you want to run flowmaster mufflers, get a ‘cat back’ system.

  2. AL M says:

    little to nothing. By removing the cat, your exhaust will just be more free flowing, without restriction.
    Youre engine will be a little more responsive, but no HP gains.

  3. Warren says:

    It could be redundant if the O2 sensor is behind the cat. If it is and you cut out the cat is will mess up the air/fuel ratio. Best to pony up for a after market cat.

  4. Kevin_57 says:

    The engine may not run right the O2 sensors are before and after the converter so the computer will not read correctly and make adjustments to the engine management system. You would be better off getting a low restriction cat to go with the new mufflers.

  5. Elmer says:

    the thing that everybody is missing is that its against the law so I wouldnt do it.

  6. T Stone says:

    none , you would loose horse power.. the modern engines are designed and tuned to be uses with converters. when you remove them it can no longer read the exhaust gas levels and set the fuel and air mixture. fuel injection engines has to have those reading to operate properly. You can replace with a high flow cat back system and make horsepower gains .. go with a high flow cat and don’t just cut them off. Also it is illegal in most states to do it .. It is a $10,000 fine to remove a catalytic converters off of a automobile that will be run on the streets . you can gain about 15 to 20% with a high performance cat back system and a bout 3 to 5% with a cold air intake if ran correctly .

  7. CV9516 says:

    Not much, if any. Plus, it’s illegal. Go with hi flow cats instead. I think flow master makes them.

  8. Kevin K says:

    it is against the law, but depending on where you live it may not matter, I live in arkansas and i’ve cut off the cat on a few of my cars, howver i’ve also put different motors in there, older v8′s with a carb setup, so it doesn’t matter. no cop is going to get under your car to see if its there. we dont have inspections here so it doesn’t matter. i would leave your cats on the car you have though.

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