Deleting cat=loss of low end torque?

[kylenautique]

I've got a 1998 K1500 with the Vortec 5.7. With all the catalytic converter theft going on, I figured I would just delete my cat before someone else does... I can tune the o2 sensor out, that is not a problem. Will this hurt or help my low end torque curve? My exhaust is stock. Would a straight pipe be better or a resonator to replace the cat?

I tow and haul stuff all the time, so screwing up that torque curve would not be ideal. My shift points have been adjusted for my tire size, TQ management is 80% reduced, and abuse mode has been removed. Black Bear tune coming soon...

Sorry if there is already a thread on this! I searched and couldn't find a definitive answer.

 

[Zerio29]

I'm not entirely sure about the torque curve on just deleting the cats... I imagine as long as you have a muffler, it wouldn't affect anything at all. Just make sure not to just hollow out the cats and put a pipe in... whether inside the cats (if you want it to look like they're still there) or just a pipe to replace the cats entirely.

The thing to watch for on these trucks is scavenging, not flow. eg. a 3.5" pipe all the way back wouldn't encourage exhaust scavenging, and even though it will outlflow a 2.5" pipe, it wouldn't perform as well because the vacuum created by an exhaust puff would be non-existent. that being said... with no actual data or results, I don't see that deleting the cat would change the exhaust flow at all, and might actually improve scavenging. just my 2 cents... maybe someone can correct me with some data on actually removing them.

The reason you won't find a definitive answer is sort of because there isn't one. There are tons of differing opinions and results online depending on your setups. Often the results you'll find online are the ones where people think that noise=power... i.e. they "felt the power a little bit" and claim to get another 10-15 horses, when in reality they just hear it more when they floor it.

 

[Supercharged111]

If you're gonna delete the cats, delete the wimpy stock headpipes too. Those are neutering the truck from an idle to redline. Have a muffler shop do you a manifold back setup if you can find one that will touch it.

 

[0xDEADBEEF]

Unless you are towing below 2500-ish rpms you won't miss them. They aren't that much of a restriction on a stock engine though.

 

[kylenautique]

Cool thanks for the info!

 

[Erik the Awful]

I'll be the naysayer and ask that you keep your cats. They don't hurt your torque at all and it keeps your environment cleaner.

The downpipes are what's hurting your power and fuel economy.

 

[kylenautique]

I'll be the naysayer and ask that you keep your cats. They don't hurt your torque at all and it keeps your environment cleaner.

The downpipes are what's hurting your power and fuel economy.

The reason I’m deleting them is because of theft. We have had a few vehicles by my work have theirs stolen. I’m only doing this because if I don’t remove it, someone will probably do it for me…. Otherwise I’d throw a high flow cat on my truck.

 

[thegawd]

Man I actually bought the y-pipe with the 2 cats, ohhhh maybe 8 years ago now and even back them it was almost $700 CAD. I still also have the oem pipe and the cats are fine. the pipe snapped up by the manifold gasket and if it was coming out to be repaired a new one was going in. I didn't have any time to F around and needed to pass an emmisions test. Ontario did away with them years ago but my truck still routinely gets more than 17MPG all these years later with a fully functional exhaust system and I absolutely agree with Erik.

If we all leave the planet a bit better than how we found it, it will be a better place for our kids and all of our futures.

I dont really care what a tune can do to trick the truck, the emmisions will be horrible.

 

[kylenautique]

Man I actually bought the y-pipe with the 2 cats, ohhhh maybe 8 years ago now and even back them it was almost $700 CAD. I still also have the oem pipe and the cats are fine. the pipe snapped up by the manifold gasket and if it was coming out to be repaired a new one was going in. I didn't have any time to F around and needed to pass an emmisions test. Ontario did away with them years ago but my truck still routinely gets more than 17MPG all these years later with a fully functional exhaust system and I absolutely agree with Erik.

If we all leave the planet a bit better than how we found it, it will be a better place for our kids and all of our futures.

I dont really care what a tune can do to trick the truck, the emmisions will be horrible.

Again, I totally get that. I’m not deleting the cats to be cool or make more power. It’s because of theft. My truck is lifted, and sits in a parking lot for 10 hours. 3 rigs have already had theirs taken. It’s only a matter of time…. I’d rather just take care of it now rather than leave work and find my exhaust hacked up.. This is the ONLY reason I’m deleting them.

 

[kylenautique]

It’s not a race truck. It’s lifted with 33s, it tows a boat, hauls firewood, goes up to the mountains, hauls my family and is my daily driver. This is why I want to make sure if I remove the cat, will there be a negative effect on my torque power band.