I know about the emissions inspection and down here in cajun country it's not a problem. Just wondering about engine trouble or anything like that.

 

It will cause only emmision problems, no running problems.

You won't even notice the gain if you remove it/gut it. It doesn't hurt performance unless it is plugged/restricted.

Why do you want it gone??

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

GO #3

 

EEEEAAAAAHHHHHHHH WRONG Engineboy. Gutting you cat causes a BIG problem with you engine. The cats internals have to heat up to a very hot temp to convert exhaust gas. Also the O2 sensor which is between the heads and the cat needs to reach 600 degrees to operate in closed loop mode (the performance mode that the car is supposed to be in when it is warmed up) Gutting the cat does not allow it to heat properly and in turn the O2 sensor will not stay at 600 degrees when the car is at idle or moving slowly (like in heavy traffic) this causes the car to go into Open Loop mode which makes the engine idle vey rough and sometimes die out. Im speaking from experiance here, see my post on this board about relocating my O2 sensor. Let me tell you though, that with Eldebrock TES headers, the gutted cat, and a flowmaster cat back this thing screams when you nail it. Sounds awesome and with very little other work im hitting 14.01 @ 99.66

This is of course assuming that you have a TPI engine, im not sure if the O2 effect TBI or electronic carbs, but im assuming that it does. Just got with a quality cat like a Random Technology cat they are the best brand out there in high flow cats. BTW car sound cats suck they burn out very quickly.

 

Trust me, I know all about the O2 needing to reach certain temps to stay in closed loop.....

I read the question as if it would HURT the engine any to run with the cat gutted.

You had other problems if removing the cat caused stalling.

Think about how many people on this board have the cat removed or gutted.

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

GO #3

[This message has been edited by Engineboy (edited September 29, 2000).]

[This message has been edited by Engineboy (edited September 29, 2000).]

 

I don't really buy that it was the cat-gutting that caused your O2 sensor problem 88. The cat would have to be a pretty big restriction to cause a significant change in the temperature of the O2 sensor. Why? Think about it, exhaust gas is moving very fast. It heats the O2 sensor as it blows by. If the cat was slowing the exhaust down enough to cause the O2 to run hotter, then that slowdown would also stall the entire exhaust, making your engine run worse. Since removing a cat does very little for performance, it's obvious that the cat isn't significantly slowing down the exhaust flow.
Your problem came from your headers and maybe a bum O2 sensor. With headers, more of your exhaust heat is lost through the walls of the headers, not to mention that the O2 sensor is also located further form the exhaust port, and therefore is colder. Combine that with an O2 sensor that is especially sensitive to temperature and there is your problem.
Having run with edelbrock headers and no cat myself for a LONG time (and no cat for even longer than the headers), i can guarantee that you had an isolated problem. TPI or not, all O2 sensors for our cars work exactly the same.
...ed

 

If it is a TPI motor I wouldn't gut it. Get a high flow cat to increase your performance. The TPI cars tend to perform better with a cat on them. This is because of the open loop mode that the computer will run in once the engine reaches operating temperatures.

------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

Gutting the cat or leaving the cat on the car will not affect open or closed loop operation. Closed loop operation is affected by many things ... most common are the closed loop delay timer and the coolant temperature. The car only needs to reach a coolant temperature of 113ºF to be able to attain closed loop (as specified in the PROM)

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

interesting, I was told it needed to be around 300-400 degrees to operate properly so to solve the whole heating issue I just bought a heated O2 sensor and eliminated any heating issues. Quick and easy fix.

As far as the cat is concerned you do need some backpressure for a fuel injected car to run properly. Of course if you have a 400hp motor then it may not help but on my 300hp 350 I had the cat removed for 2 weeks while I had my Edlebrock headers and my Dynomax cat-back. While it had a nice, wonderful sound I notice I lost some hp believe it or not. At first I thought it was a fluke but during htose 2 weeks I began to realize I was loosing hp with the straight pipe on. When I put the high flow cat back on I noticed an increase in hp. Many magazines have done test on open exhaust, with headers and mufflers, and with headers, cat and mufflers and proved that a cat will only cost you 5 hp! I did love the sound though and would love to go back without a cat. It did attract a few cops who tailed me for a few miles b/c the car sounded very loud.

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1988 TA 300+hp 350 w/ TBI and Holley TB unit,
WC T-5, 3.42 gears w/ Auburn posi. MSD 6A, edelbrock TES headers, dynomax 3" cat and cat-back system, ACCEL coil, polyurethane bushings all around, aluminum driveshaft, Mr. Gasket open air cleaner.

1993 S-10 w/ 4.3L V6 TBI, slightly bigger cam, Mild polish job and 3 angle valve job on heads, Edlebrock TES headers, Dynomax cat back, MSD 6A, ADS chip
(bought from my dad)

2000 GMC Sierra Regular Cab Stepside
285hp 5.3L w/ 3.42 gears and locking diff. (sold to my dad..no!!)

 

Badbird,

When I said 113º I was referring to the coolant temperature ... not O2 sensor temperature. The ECM does not keep track of O2 sensor temperature.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Thanks for the the correction. Learn something new everyday. So why would the O2 sensor matter if it was heated or not if the ECM doesn't record/read the O2 sensors temperature?