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C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

L98 Catalytic Converter

 
Old 06-02-2019, 11:00 AM
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stngry63
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Default L98 Catalytic Converter

It's time to pass an emissions again, and I don't think it's going to happen. Last year it barely passed. Since then, the AIR pump seized and has been removed. Apparently, it's a one year only part. I would have put another back on, but it was either not available or would go on back order at check out. Also, one of the front converters is rattling.

I am thinking of removing the front catalytic converters and going with a single OBDII type in the rear. Has anybody passed an L98 on an emissions tail pipe test with an OBDII catalytic converter that doesn't have an AIR fitting?
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Old 06-02-2019, 11:30 AM
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ctmccloskey
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I bought an aftermarket catalytic Converter from Summit and it was a "Universal" that just happened to match right up with the C4's system, it even had the air pipe and came with a cap on the end of the tube. The instructions that came with the converter said to cap it off if not needed. I then put a chambered exhaust behind it. The first time I went to get the Emissions tested it passed with much better numbers than previous years. The catalytic converter that I bought had a higher flow rate than the restrictive original design. I paid about $150 for the universal and it has been great ever since. The car gained just shy of 14 hp with the new catalytic the chambered exhaust so in the end I would call it a "worthwhile project".

The front Y pipe has those little bulges in it and I have heard them called "Pre-Catalytic" converters. I am not sure why they are right there in that location because if they were truly catalytic converters they would be generating a ton of heat inside the engine compartment. I would remove them and empty them out and re-install the empty shells so they "appear" to be all there. This should solve the rattling issue once and for all.

Good Luck with your project! Use a decent quality aftermarket catalytic converter and you will probably have no trouble passing the emissions testing as long as everything else is working or tuned properly. If it needed AIR pumped into the catalytic use an aquarium air pump while the Corvette is being tested and removed the minute it passes..
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Old 06-02-2019, 02:20 PM
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Thanks!
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Old 06-05-2019, 10:49 AM
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3D-Aircrew
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I removed the pre-cats and installed a y-pipe and main hi-flo cat. I don't have inspections and the car is louder now.
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Old 06-05-2019, 02:01 PM
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coupeguy2001
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I have a front Y pipe with the front flanges cut off.
I can send the front precats so you can weld them back on to your pipes for $65 shipped.
602-510-2519 Chris
Call Larry at 20th Street Auto for the air pump. He just might have a couple sitting around..602-258-2020

Last edited by coupeguy2001; 06-05-2019 at 02:05 PM.
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Old 06-05-2019, 09:31 PM
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CorvetteRules
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Move to NJ, Cars 95 and older don't have to be inspected.

Last edited by CorvetteRules; 06-05-2019 at 09:32 PM.
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Old 06-06-2019, 05:11 PM
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coupeguy2001
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but then you have to live in NJ
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Old 06-06-2019, 05:17 PM
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vette196
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Originally Posted by CorvetteRules View Post
Move to NJ, Cars 95 and older don't have to be inspected.
I wouldn't do it.....what I pay per month in taxes is equal to a full year in other areas of the country
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Old 06-06-2019, 08:55 PM
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Originally Posted by coupeguy2001 View Post
but then you have to live in NJ
You got me there, but it could be worse, I could live in West Virginia LOL
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Old 06-07-2019, 01:02 PM
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cmontel727
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I believe a new hi flow cat will get you through emissions. When I had to take mine through emissions testing it did better without all the stock equipment. Air pump, egr, and precuts removed. New cats are much more efficient then ones from the eighties.

Good Luck
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Old 06-07-2019, 02:03 PM
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vetteLT193
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Since you are in Tenn based on your profile... why not go Antique plates? Once you get the Antique plates (25 year old cars and older) then you bypass the inspection. Plus, if it is anything like FL, antique plates are cheaper to renew as well.
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Old 06-08-2019, 02:33 AM
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My first 35th Anni had a 2 1/2" mandrel bent Y, Random Tech cat and TPIS cat-back and easily passed the OH sniffer test each time.
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Old 06-09-2019, 10:38 PM
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stngry63
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Originally Posted by vetteLT193 View Post
Since you are in Tenn based on your profile... why not go Antique plates? Once you get the Antique plates (25 year old cars and older) then you bypass the inspection. Plus, if it is anything like FL, antique plates are cheaper to renew as well.
I drive my car on any given day. In Tennessee, antique plates are only valid for weekends and car events. I'm not worried about a ticket so much as not being covered by insurance for a non agreed use of the car by getting a ticket in an accident. My insurance agent had a client who was denied a claim for delivering pizzas on a personal policy instead of on a commercial one. I recently gave a ride to a used car dealer at a grocery store because the police seized his car after a minor accident. He was using the car for personal use on commercial dealer tags. I talked to an acquaintance who used to be a policeman. They frown on that.

Last edited by stngry63; 06-09-2019 at 11:13 PM.
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Old 06-10-2019, 03:59 AM
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FWIW - on my 85, I upgraded and installed an 86-91, walker front Y-pipe assembly. it comes pre-catless, and with a hi-flow main cat. stainless and mandrel bends. nice hardware - no installation issues. as for the smog pump, can't help you there....

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Old 06-10-2019, 12:50 PM
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Originally Posted by Joe C View Post
FWIW - on my 85, I upgraded and installed an 86-91, walker front Y-pipe assembly. it comes pre-catless, and with a hi-flow main cat. stainless and mandrel bends. nice hardware - no installation issues. as for the smog pump, can't help you there....
I bought a roof panel off of craigslist this morning, and the seller also had a working 1986 smog pump laying around in his garage that he had pulled off of his race car. So I picked it up too. I found a shop that will replace all three cats with a single universal.
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Old 06-11-2019, 10:26 AM
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vetteLT193
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Originally Posted by stngry63 View Post
I drive my car on any given day. In Tennessee, antique plates are only valid for weekends and car events. I'm not worried about a ticket so much as not being covered by insurance for a non agreed use of the car by getting a ticket in an accident. My insurance agent had a client who was denied a claim for delivering pizzas on a personal policy instead of on a commercial one. I recently gave a ride to a used car dealer at a grocery store because the police seized his car after a minor accident. He was using the car for personal use on commercial dealer tags. I talked to an acquaintance who used to be a policeman. They frown on that.
That sucks. In FL there are no restrictions.
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Old 06-11-2019, 10:50 AM
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Originally Posted by vetteLT193 View Post
That sucks. In FL there are no restrictions.
- no restrictions and $21.50 for plates. it's a win-win....
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Old 06-12-2019, 04:51 PM
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Don't fool around.... The rattling pre-cat will come apart and you will think your transmission is going out. It will fall down and plug up your main cat. The car just won't go, with no power you'll keep mashing the gas and the transmission will shift up and down like a yoyo. Ask me how I know....
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