removing cats

I'm suspecting my cats are stopping up and I wanna cut them. I'm assumiong this will cause gas mileage to decrease and the valves to rattle some..power is also down from what it used to be.

Here's my question. If I do, how much low-end can I expect to loose? I'm not really fond of loosing any low end torque if I can help it. Any pros/cons I don't know about? I don't have emission testing here..so thats not a problem. I know I'll have to get the rear 02 sensor's disabled.

a CON would be it's a federal offence to do so, regardless of your
states emmision testing or lack there of.

I cut mine and really actually gained some, I had a 2.25" catback before and you having a 2.5" I would believe the extra flow you will receive to your flows will only help your cause a bit on the low-end torque. The removal of the cats also really opened up the sound of my flow. My top end however is alot better!

Chris

Well, Im not really worried about the EPA or anything right now. If they want me to leave my cats on, the federal folks can lower gas prices.

I am very interested in what will happen if i take mine off. I have a stock setup to flowmaster 40 series. 1 in 2 out with 2 1/2 pipe. Im at 70 thousand miles on my truck. So will it add power, gas mileage all that. Will i loose any power anywhere in my powerband. Is it worth it to take them off right now?

I cut mine off, the truck is smoother throughout the powerband with them off acutally, allen can tune out the rear o2's for ya too!

Chris

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Originally posted by JayBo@Feb 23 2005, 01:40 PM
I'm suspecting my cats are stopping up and I wanna cut them. I'm assuming this will cause gas mileage to decrease and the valves to rattle some..power is also down from what it used to be.

Here's my question. If I do, how much low-end can I expect to loose? I'm not really fond of loosing any low end torque if I can help it. Any pros/cons I don't know about? I don't have emission testing here..so thats not a problem. I know I'll have to get the rear 02 sensor's disabled.

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Cutting your cats is NOT gonna help your gas mileage. Bad A/F ratio, so yes you will have to get the rear O2s deleted. Power gain will be noticeable in the top end, but low end will lose due to a backpressure issue. I honestly don't think you'll notice much power difference at all.
However, you will sound louder than hell and kill off the local ozone around your house. :laugh:
The best thing you can do is just bite the bullet and buy some more cats, preferably high flow. Because if you get a ticket for disturbing the peace, or something retarded like that, you will wish you would have just replaced them.

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Originally posted by kinjo1977@Feb 24 2005, 10:16 AM

Cutting your cats is NOT gonna help your gas mileage. Bad A/F ratio, so yes you will have to get the rear O2s deleted. Power gain will be noticeable in the top end, but low end will lose due to a backpressure issue. I honestly don't think you'll notice much power difference at all.
However, you will sound louder than hell and kill off the local ozone around your house. :laugh:
The best thing you can do is just bite the bullet and buy some more cats, preferably high flow. Because if you get a ticket for disturbing the peace, or something retarded like that, you will wish you would have just replaced them.

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i would have to agree with this logic :duh: and for arguments sake, the article on the bolt on C6 in Pop. Hot Rodding this month, they actually gained like 2rwhp by putting some highflow cats on the car vs. no cats at all :eek: BEATS the heck out of me, i would've never figured it. But even if it was a fluke, you at least know they arent costing you any horsepower and you are being a "goodboy" all at the same time. I dunno, Just thoughts

I guess I'll keep them then. So what kind do you suggest I replace them with? I dunno alot about cat's...all I've ever dun is cut em off.

Cutting the cats has nothing to do with A/F ratio, all they are there for is catalytic efficiency. I had the same question for Allen when dong my tune and thats the answer I got.

Chris

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Originally posted by JayBo@Feb 25 2005, 06:55 AM
I guess I'll keep them then. So what kind do you suggest I replace them with? I dunno alot about cat's...all I've ever dun is cut em off.

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i've always seen ~10HP gain by taking off the factory cats on other boards. I Myself, like you, have always just cut'em off. But given the quality of some of the new highflow cats that are available i wouldnt mind having some back on my car, the only reason i havent is $$$$. I would say the best ones are most likely going to be the most expensive.

here is an example of the style of cat that all the "gurus" say is the best

dynatech cats

another option might be some low milage cats from a salvaged HD silverado?

I put magnaflow high flowcats on my truck after having straight pipes then mufflers then i finally put some high flow cats on(to loud in the morning the neighbors started giving me dirty looks). I noticed a gain in the low end and lost just a hair in the top end with the high flow cats. I would put them on again if i had to do it all over again.

I guess its time to save some moolah and get those high-flow ones. Is that the only decent brand, or are there more that might be a tad less expensive?

I took mine off and gained almost 50HP!!!! oh, I guess a plugged up turbo would be better off with no cats. :laugh:

allen

I can't afford a turbo yet :cry:

I went with the magnaflows because they are stainless(only have to do it once) and they fit nicely under the truck cause they arent round if you need a part number i have the one for 2.5 inch pipes ill try and dig it up if you need it.

So I will need some with 2.5" inlets/outlets? that was a question of mine also. I don't want to sloppy lookin junk under there when I put them on.