cat on my diesel

We don't have emissions testing here in Florida, but I can imagine that altering the pollution control systems in most any way on a vehicle in a state that does have these tests will be a problem. The cat is there for a reason after all, as is the plethora of sensors and valves put on at the factory. Your LLY motor generates more power than my LB7 version but only emits less than one-fifth (or less) of the pollution mine does. That was a hard mark to meet (it actually meets the 2007 EPA emission standards), and I don't think removing the cat will help you maintain those levels - not to mention possibly voiding your warranty because GM, like all manufacturers, have certain taboos on altering the emission systems.

My question is, on a vehicle that is generating 320 HP and 590 ft-lbs of torque just what do you hope to gain? You could get a cat that has larger diameter openings and flows more freely than a stock unit, but for what you're going to pay for everything when you're done all you'll be getting is a few extra HP and ft-lbs of torque, and maybe a lot more noise. Hardly seems worth the price on a truck that is that powerful to begin with.

Just my two cents worth - Jonathan

Even though Florida no longer sticks a sniffer up our tail pipes, it is still illegal to remove, bypass or disable emission control devices on a motor vehicle. If clean air indexes drop below federal EPA guidelines testing could come back.

I do agree with you whole heartedly as to it not being worth the effort to remove it or replace with a performance cat unless he is going to go full ape on it, by which I mean ECM controllers, improved intake system, propane and or nitro. Any of which will void the warranty. The horsepower and torque on that engine as it is will pull anything that is within the rest of the vehicles capabilities (like brakes, steering, suspension) with out a groan.

As the original poster asked "or I'm I going to be in trouble when I go for my smog test?" then removing it is a no no cause it clear he's in the 80% region cox.net covers that does smog test.

Whitelightning

And if he gets more power he will have to upgrade the transmission too. The transmission is rated at the torque limit that the engine puts out. It was noted here a while ago that the manual transmission has lower torque limits, and appears that the computer must be programed to limit the engine output with that transmission.

From: "Jo" To: "me" Subject: Re: cat on my diesel Date: Monday, February 21, 2005 5:13 AM

Thanks for the input. I am of the same opinion as most of you. I think the cat should stay on the truck. I need to find a bigger one to match the exhaust tube diameter. I should mention that I use this truck to pull very heavy loads up fairly big hills in my business. I already have an upgraded trany and have add more power through the use of an Edge Juice upgrade. I don't think Chevy is going to cover my truck under warranty. The exhaust is to make the engine breath a little better for add HP and to try to get a little more fuel mileage. As far as the noise, I'll just turn up the XM radio.

----- Original Message ----- From: "me" Newsgroups: alt.trucks.chevy Sent: Saturday, February 19, 2005 7:29 PM Subject: cat on my diesel

Just remember that increasing air flow in and out helps the upper end of the rpm band, at the expense of the lower end of the rpm range. And with the right components just because you went bigger doesn't mean it has to be a whole bunch louder. With all of this that you are doing I would want a pyrometer gauge on the exhaust close to a manifold, on rigs with turbos, as close to turbo as possible.

Whitelightning

Already have a pyrometer. It sounds like you know your stuff. Thanks for the help.

Not really a "catalytic converter" but more of a soot trap.

Unless the cat's clogged up, I'd say leave it alone.

Nevertheless, you could gut it and reinstall it just in case an inspector wanted to check if you still have a "cat" installed -- it'd be another thing if he/she wanted to dismantle the exhaust system to see if you've gutted the cat.

Franko