Dyno Results From Gutted Cats
06-08-2007, 10:37 PM
#21
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I heard that if you gut a cat you will get terbulance because the air goes from a 3" round pipe to a ~5" oval pipe, than Back to a 3". Is that true or just BS. I instead cut mine off, and welded a 3" pipe in place. I can hear a diffrence, and it seams to get better gas mileage, and noticable HP gain, (Stock Engine), but seems to have lost a little torque. Maybe im just diffrent but thats what i have noticed.
Plus I love that smell you were talking about.
Plus I love that smell you were talking about.
06-09-2007, 04:35 AM
#22
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I thought the same thing about the turbulence, until I looked into the hollowed out cats. I'm sure there is some turbulence, but obviously not enough to outweigh the benefits of gutting them. A 3" pipe would be best, but I wanted to at least have cats underneath should some cop stick his little mirror under my car, because it is very loud under WOT.
My torque actually went up!
Remember when GM sent out that bulletin that if you experience any "problems", to have your cats tested because many of them were failing. I was experiencing some performance issues and low and behold, one of my cats failed the test so both were replaced under warranty.
In the process of changing them, the dealership stripped the threads on one of my O2 sensors so instead of buying AC Delco @ $140 each, I bought NGK from Summit for a third of the price.
I got my gutted cats free, from a friend. They were from a 2001. Instead of tying up the dangling wire from the rear O2 sensors once I plugged in the sims, I cut the wires off two of my old GM sensors made sort of a plug out of them so if anyone looks under my car, it looks like two stock cats with all the O2 sensors hooked up. I still have a set of new stock cats should I ever decide to change them back. We don't have any sort of testing at all where I live anyway.
The smell is great. You don't smell anything inside the car, but the person sitting behind can smell it. It just smells like any other Saturday at the drag strip.
My torque actually went up!
Remember when GM sent out that bulletin that if you experience any "problems", to have your cats tested because many of them were failing. I was experiencing some performance issues and low and behold, one of my cats failed the test so both were replaced under warranty.
In the process of changing them, the dealership stripped the threads on one of my O2 sensors so instead of buying AC Delco @ $140 each, I bought NGK from Summit for a third of the price.
I got my gutted cats free, from a friend. They were from a 2001. Instead of tying up the dangling wire from the rear O2 sensors once I plugged in the sims, I cut the wires off two of my old GM sensors made sort of a plug out of them so if anyone looks under my car, it looks like two stock cats with all the O2 sensors hooked up. I still have a set of new stock cats should I ever decide to change them back. We don't have any sort of testing at all where I live anyway.
The smell is great. You don't smell anything inside the car, but the person sitting behind can smell it. It just smells like any other Saturday at the drag strip.
06-09-2007, 04:40 AM
#23
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Originally Posted by LS1-450
Nice numbers. I'm gutting my cats in the Fall. You mentioned making power for 1k RPM more than in your previous dyno run. Is the 13 RWHP @ the 1K higher RPM or was it measured @ the same RPM as the previous pull?
06-09-2007, 07:58 AM
#24
Originally Posted by Marblehead
My last run, last month, I was making peak HP at 5700. With the gutted cats, I'm making peak HP at 5800. I hope that's what you were looking for.
Your post said a 1K RPM (1000 RPM) increase. HP is a result of engine speed & torque. So, if there had been an increase of 1000 RPM, then your HP increase would have been a result of engine speed. @ just 100 RPM increase, the HP gain is negligable & is the likely result of the gutted cats.
You may pick up a little more HP with a tweak in the A/F ratio. She looks a bit lean early & too rich @ the end. 12.9 to 13.0 @ 5,900 RPM could give you a little more. The early lean condition may be causing knock. This would make the knock sensors pull timing & cause the early dip in torque.
06-09-2007, 09:04 AM
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Originally Posted by LS1-450
Your post said a 1K RPM (1000 RPM) increase. HP is a result of engine speed & torque. So, if there had been an increase of 1000 RPM, then your HP increase would have been a result of engine speed. @ just 100 RPM increase, the HP gain is negligable & is the likely result of the gutted cats.
You may pick up a little more HP with a tweak in the A/F ratio. She looks a bit lean early & too rich @ the end. 12.9 to 13.0 @ 5,900 RPM could give you a little more. The early lean condition may be causing knock. This would make the knock sensors pull timing & cause the early dip in torque.
You may pick up a little more HP with a tweak in the A/F ratio. She looks a bit lean early & too rich @ the end. 12.9 to 13.0 @ 5,900 RPM could give you a little more. The early lean condition may be causing knock. This would make the knock sensors pull timing & cause the early dip in torque.
Thanks for the A/F info.
06-09-2007, 10:46 AM
#26
Originally Posted by Marblehead
Do you think your the only one who has knowledge on this subject? Trust me, everything was the same. I got 13 RWHP from this mod. I don't give two hoots if you believe the numbers or not. I posted this because I could find no info around here on this mod alone. The dyno shop that you speak of is one that I would not waste my time with.
06-09-2007, 10:48 AM
#27
Originally Posted by 5_02ls1
my 3 year old daghter flips better **** than that.....
ive seen as much as .2 gained in the 1/4 by gutting cats.....
have you ever seen the inside of a factory cat??????
probably not
06-09-2007, 07:05 PM
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Originally Posted by BlackSVT03
woah, relax there buddy. Sand in your Vaseline or something?
And why is your "mods list" link in your sig go to a blog on my Myspace page? What kind of freak are you? Creepsville.
06-09-2007, 07:21 PM
#30
Yeah ok buddy. Was I claiming to be a "smart *** know-it-all"? I didnt think so. My apologies for your misconception.
Just contributing my two cents. Youre the one who got all defensive when I said something.
Just contributing my two cents. Youre the one who got all defensive when I said something.
06-09-2007, 07:38 PM
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Originally Posted by BlackSVT03
Yeah ok buddy. Was I claiming to be a "smart *** know-it-all"? I didnt think so. My apologies for your misconception.
Just contributing my two cents. Youre the one who got all defensive when I said something.
Just contributing my two cents. Youre the one who got all defensive when I said something.
