Improvement By Changing Cats?
Thread Starter
Burning Brakes
Joined: Dec 2000
Posts: 1,161
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From: Orangeburg, NY
Improvement By Changing Cats?
I have an 89 auto and it runs pretty well. The car has over 100k and I am tinking of replacing the front pipe (with precats) and the catalytic converter. Will changing them out make any significant difference? Do I really need the precats or would a regular front pipe pipe be ok? There are some significant price differences in cats. What's the real difference between them?
I have checked the catalytic converter and is does not appear to be clogged, nor is it glowing red. As I said, the car runs pretty well, idles nicely, gets decent gas mileage, but I want to get the most out of the car, while keeping it realitively stock. Any thoughts?
I have checked the catalytic converter and is does not appear to be clogged, nor is it glowing red. As I said, the car runs pretty well, idles nicely, gets decent gas mileage, but I want to get the most out of the car, while keeping it realitively stock. Any thoughts?
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Most muffler shops will not remove a cat on a licensed street-driven car. It's a violation of federal law and the shop can get hit with a substantial fine (in 5 figures
) should they get caught.
Removal of the cats can result in a HP gain and also a big increase in exhaust noise. Then there is the emissions issue. Do you live in an area that requires an emissions test (sniffer or visual or both) to get the plates renewed?
Having said that, Corvette Central has a true dual exhaust sysyem that is a bolt-in install and allows the use of any muffler designed for the C4. There is a 02 sensor bung installed in the correct location.
As far as price differences in cats, that probably depends on the maker or whether or not it's a universal-style fit or is a direct fit. The universal design typically requires some welding where an direct fit is designed to bolt in just like the factory cat. Some cats are a high-flow design that can improve the flow of the exhaust through the cat and still provide emission reductions to meet state requirements.
) should they get caught.Removal of the cats can result in a HP gain and also a big increase in exhaust noise. Then there is the emissions issue. Do you live in an area that requires an emissions test (sniffer or visual or both) to get the plates renewed?
Having said that, Corvette Central has a true dual exhaust sysyem that is a bolt-in install and allows the use of any muffler designed for the C4. There is a 02 sensor bung installed in the correct location.
As far as price differences in cats, that probably depends on the maker or whether or not it's a universal-style fit or is a direct fit. The universal design typically requires some welding where an direct fit is designed to bolt in just like the factory cat. Some cats are a high-flow design that can improve the flow of the exhaust through the cat and still provide emission reductions to meet state requirements.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
I can't address the precats. Cats have improved since 89. By getting a high flow cat, you should be opening the exhaust which should give you more performance.
I replaced my original with a Magnaflow high flow and noticed a difference. Then I was looking at the old one one day (which was broken up inside) and thinking of the new one (which you could see thru the honey comb) and thought.....you are still in effect necking down a 2-1/2" pipe to perhaps 1-1/2" with all this stuff in the converter. So I cut off the old flanges off the 85 converter and built my own straight thru pipe.
It measured 4-3/8" x 2-3/4". I bolted this up the next time I went to the track and dropped .5 seconds in the 1/4 mile. Went from 14.1 to a consistant 13.6. This was with the old motor. I use this ONLY for the track.
I replaced my original with a Magnaflow high flow and noticed a difference. Then I was looking at the old one one day (which was broken up inside) and thinking of the new one (which you could see thru the honey comb) and thought.....you are still in effect necking down a 2-1/2" pipe to perhaps 1-1/2" with all this stuff in the converter. So I cut off the old flanges off the 85 converter and built my own straight thru pipe.
It measured 4-3/8" x 2-3/4". I bolted this up the next time I went to the track and dropped .5 seconds in the 1/4 mile. Went from 14.1 to a consistant 13.6. This was with the old motor. I use this ONLY for the track.
Last edited by John A. Marker; Jun 7, 2008 at 10:09 AM.
Drifting
Joined: Oct 2006
Posts: 1,934
Likes: 3
From: Citrus Heights California
You could replace your front Y pipe with 2 1/2" pipe and two of these hi flow OBD 11 compliant 50 state legal bullet cats. http://store.summitracing.com/partde...part=pye-cvm13
Then you could eliminate your main cat and put an X pipe where the main cat goes. Then run cat backs. Then you'll have 2 1/2' dual exhaust with a two hi flow cats.
Check your state laws. I think most states will allow it as long as the emissions are OK.
http://store.summitracing.com/partde...5&autoview=sku
Then you could eliminate your main cat and put an X pipe where the main cat goes. Then run cat backs. Then you'll have 2 1/2' dual exhaust with a two hi flow cats.
Check your state laws. I think most states will allow it as long as the emissions are OK.
http://store.summitracing.com/partde...5&autoview=sku
Last edited by Kool88vette; Jun 7, 2008 at 12:18 PM.
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
I put this set up on my 86 roadster a few years back. This configuration eliminated my front cats which were pretty much plugged. The result was a very noticable increase in power, gas mileage and a deeper and louder exhaust note. The car continues to pass ALL state emissions tests. Here is where you can get these replacement parts:
http://www.ecklers.com/product.asp?p...8&dept_id=1777
My local Chevrolet dealer had no problem with the changeout as long as I replaced the main cat with a new unit and it passed the state test. Also, there is a Federal form that you have to fill out when changing out the original cat. The form comes with the new cat and is no problem to fillout and give to the dealer/installer.
My recommendation is that you go ahead and make the change. You will be glad that you did.
http://www.ecklers.com/product.asp?p...8&dept_id=1777
My local Chevrolet dealer had no problem with the changeout as long as I replaced the main cat with a new unit and it passed the state test. Also, there is a Federal form that you have to fill out when changing out the original cat. The form comes with the new cat and is no problem to fillout and give to the dealer/installer.
My recommendation is that you go ahead and make the change. You will be glad that you did.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Since you are in Orangeburg, NY I must strongly warn you to not go to the local muffler shop on Rt 59 in Nanuet....
There are two options on getting rid of the front Y:
-buy a mandrel-bent 2 1/2" unit from say MAM
-have Denny's boys at Mufflex in Trenton, NJ (link on my site) custom build a front Y for you. They charged me about the same $$ as would have cost to buy the unit from MAM and do it myself. Doing the front Y & hi-flow main cat gained me about 15chp, and did the same for Vic89.
Consider that your '89 puts out around 255chp (the frisbee is sucking up 10chp). If exhaust flow is below 2.2cfm/1chp there will be some power loss due to back pressure. For your '89 you need an exhaust to flow >560cfm; that is asking quite a bit from a single OEM cat, IMO.
Do the exhaust mods and toss the frisbee (see my link) from the water pump pulley and you will gain around 25chp.
BTW, my '88 is registered in OH and, with such exhaust mods and a 160deg T-stat she still easily passes the OH E-Check emission test with 176k miles on the clock...
There are two options on getting rid of the front Y:
-buy a mandrel-bent 2 1/2" unit from say MAM
-have Denny's boys at Mufflex in Trenton, NJ (link on my site) custom build a front Y for you. They charged me about the same $$ as would have cost to buy the unit from MAM and do it myself. Doing the front Y & hi-flow main cat gained me about 15chp, and did the same for Vic89.
Consider that your '89 puts out around 255chp (the frisbee is sucking up 10chp). If exhaust flow is below 2.2cfm/1chp there will be some power loss due to back pressure. For your '89 you need an exhaust to flow >560cfm; that is asking quite a bit from a single OEM cat, IMO.
Do the exhaust mods and toss the frisbee (see my link) from the water pump pulley and you will gain around 25chp.
BTW, my '88 is registered in OH and, with such exhaust mods and a 160deg T-stat she still easily passes the OH E-Check emission test with 176k miles on the clock...
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
I have an 89 auto and it runs pretty well. The car has over 100k and I am tinking of replacing the front pipe (with precats) and the catalytic converter. Will changing them out make any significant difference? Do I really need the precats or would a regular front pipe pipe be ok? There are some significant price differences in cats. What's the real difference between them?
I have checked the catalytic converter and is does not appear to be clogged, nor is it glowing red. As I said, the car runs pretty well, idles nicely, gets decent gas mileage, but I want to get the most out of the car, while keeping it realitively stock. Any thoughts?
I have checked the catalytic converter and is does not appear to be clogged, nor is it glowing red. As I said, the car runs pretty well, idles nicely, gets decent gas mileage, but I want to get the most out of the car, while keeping it realitively stock. Any thoughts?
