Unless the cats are plugged, all you'll get is noise. You might have trouble when it gets time to sell.
Catalytic Converter Question
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,218
Likes: 2
From: Plainfield IL
Catalytic Converter Question
My '86 is exempt from state emissions testing. I want to replace the catalytic converter with a straight pipe to improve performance and sound. Will this create any problems?
Race Director
Joined: May 2006
Posts: 10,691
Likes: 71
From: Phoenix Arizona
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Your car actually has 3 cats. Each exhaust pile has a pre-cat and the main cat is where the front Y-pipe connects to the single pipe that goes to the rear.
You can remove the pre-cats either by buying a new pipe that does not have the pre-cats or simply cut them out and replace them with straight pipe.
Most muffler shops will not remove the cats from a car. There is a huge (5 figures
) fine for any shop that gets caught removing working cars from a car.
Long tube headers are a great way to improve performance, but they can be expensive (Hedman Elites p/n 68448) can run over $400) and you still have to have them connected to the main cat.
True duals will work but unless you have a good set of mufflers, it will be loud with some interior resonance.
In either application, you will have to keep the O2 sensor connected so that the computer will go into closed loop mode for efficient operation. Headers will require a way to connect the EGR tube. The AIR pump can stay on the car and there are headers that have provisions for the AIR hookups.
There are some cat-back systems that wil provide some power increase and a nice sound and all you have to do is to unbolt the pipe behind the factory cat and install the system. Probably a much better way to go to get what you are after.
You can remove the pre-cats either by buying a new pipe that does not have the pre-cats or simply cut them out and replace them with straight pipe.
Most muffler shops will not remove the cats from a car. There is a huge (5 figures
) fine for any shop that gets caught removing working cars from a car.Long tube headers are a great way to improve performance, but they can be expensive (Hedman Elites p/n 68448) can run over $400) and you still have to have them connected to the main cat.
True duals will work but unless you have a good set of mufflers, it will be loud with some interior resonance.
In either application, you will have to keep the O2 sensor connected so that the computer will go into closed loop mode for efficient operation. Headers will require a way to connect the EGR tube. The AIR pump can stay on the car and there are headers that have provisions for the AIR hookups.
There are some cat-back systems that wil provide some power increase and a nice sound and all you have to do is to unbolt the pipe behind the factory cat and install the system. Probably a much better way to go to get what you are after.
Racer
Joined: Mar 2008
Posts: 254
Likes: 0
From: Perth W.A
How about keeping the precats and ditching the maincat, adding a xpipe(dual pipes) to reduce drone! and then into mufflers?
would ditching either precats or maincat(one or the other) effect the L98 torque? what would be best?
would ditching either precats or maincat(one or the other) effect the L98 torque? what would be best?
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,218
Likes: 2
From: Plainfield IL
What's causing the cabin resonance or drone? I used to own an '81 Vette. When I replaced the catalytic with a test tube (straight pipe), there was no drone, just a better exhaust note and better flow.
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Instructor
Joined: Nov 2009
Posts: 155
Likes: 2
From: Columbiana AL
My brother removed the main cat from his 91 with no ill effects. He left the mufflers, and it really had a nice sound under WOT, no drone at any speed. It did seem to wake the car up. He also removed the frisbee.
Racer
Joined: Mar 2008
Posts: 254
Likes: 0
From: Perth W.A
Oh ok, i just thought that having no main cat would cause drone as it is right under the seating area! But it seems it doesn't! thanks!
Also this frisbee! is it safe to remove this! i am assuming it is there to keep the belt on!? or maybe balance the pulley? what sort of gains are to be had by removing it?
thanks
Also this frisbee! is it safe to remove this! i am assuming it is there to keep the belt on!? or maybe balance the pulley? what sort of gains are to be had by removing it?
thanks
Instructor
Joined: Nov 2009
Posts: 155
Likes: 2
From: Columbiana AL
The frisbee is about 5-10 pounds of useless reciprocating mass. Its only purpose in life is to smooth the transition of the AC compressor clutch cycling on and off. It is simply a flywheel. You don't need it, and the motor revs more freely without it.
Racer
Joined: Mar 2008
Posts: 254
Likes: 0
From: Perth W.A
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
I took my exhaust system off and replaced them with LT headers and Borla exhaust. That took care of the pre-cats. I also put a Random Tech cat on it because I wanted to get rid of the drone from a hollowed out cat.
I don't believe true duals will help much. I tried to run the exhaust with the front "Y" disconnected and the times didn't change much.
I don't believe true duals will help much. I tried to run the exhaust with the front "Y" disconnected and the times didn't change much.
