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  #1  
Old December 28th, 2004, 14:32
ParkCityXJ ParkCityXJ is offline
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No cat mileage

Has anyone noticed a change in mileage (good or bad) when removing the catalitic converter, or changing to a high flow cat??
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  #2  
Old December 28th, 2004, 14:40
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Ron4x4 Ron4x4 is offline
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Re: No cat mileage

I redid my whole exhaust with a header, high flow cat and a terminator muffler with 2.5 an 3 inch pipe and I do get about 60 more miles per tank.
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  #3  
Old December 28th, 2004, 15:32
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Re: No cat mileage

I put in a new high flow cat, glass pack, & tail-pipe and noticed about 1 mpg increase in gas mileage (I calculate my mileage with each fillup by dividing the miles driven by the gallons to fill it up).
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Old December 28th, 2004, 16:33
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Mikel Mikel is offline
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Re: No cat mileage

Keep in mind that these numbers are probably with people ditching their old exhaust and old cats. It's like people who get a new carb and say it's so much better than their 22 year old original, un-rebuilt carb!
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Old December 28th, 2004, 16:51
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Re: No cat mileage

There's no probably about it, we stated exactly what changes we'd made.
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  #6  
Old December 28th, 2004, 17:27
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Harvo Harvo is offline
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Re: No cat mileage

My cat is gone and it seemed to hurt my milage. My wife was driving it at the time though, so I couldn't tell you definitively how much.
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  #7  
Old December 28th, 2004, 17:55
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Re: No cat mileage

I'm waiting on a gasket for my exhaust, right now I've been running downpipe only, and it has definitely hurt my gas mileage, I lost about 3 mpg.
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Old December 28th, 2004, 18:19
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Re: No cat mileage

I put a 2.5in cat & resonator on and have gained about 2 mpg. On a side note, I lost MPG when I staight piped my YJ.
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  #9  
Old December 29th, 2004, 00:10
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Re: No cat mileage

I also ran just a header and down pipe for a couple weeks before putting the rest on, and it hurt my mileage and power quite a bit.
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