Benefits of Removing Cat and Running Straight Pipe?

[Bdaslug]

I gutted my cat. and also I made my piping larger than stock. now I have a 2.5 in exhaust all the way. without the cat it's get a little bit louder. Depending if you have a straight through muffler like a N1 style. But it doesnt sound like a honda. Also your gas mileage will go down alot, Because the check engine light stays on without the cat. I actually tried both O2 simulators (mechanical and electrical) and the check engine light still comes on after a few miles. But you can feel the difference from the stock 1-3/4 inch to 2-1/2inch piping only at higher speeds. I am going to install a high flow cat to get rid of the check engine light and it should help my gas mileage a bit.

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Originally Posted by Bdaslug

I gutted my cat. and also I made my piping larger than stock. now I have a 2.5 in exhaust all the way. without the cat it's get a little bit louder. Depending if you have a straight through muffler like a N1 style. But it doesnt sound like a honda. Also your gas mileage will go down alot, Because the check engine light stays on without the cat. I actually tried both O2 simulators (mechanical and electrical) and the check engine light still comes on after a few miles. But you can feel the difference from the stock 1-3/4 inch to 2-1/2inch piping only at higher speeds. I am going to install a high flow cat to get rid of the check engine light and it should help my gas mileage a bit.

The check engine light for cat inefficiency (code (p0420) has no effect on anything. You mileage went down because your exhaust piping is too big and you lost low end power. 2.5 inch piping is too big for a 100 HP car.