Catalytic Converter Caused Poor Performance What ia a good replacement
 

!990 Coup 6MT removed the front half of the exhaust and then removed the cat from the Y pipes the front half of the cat was shattered.Any ideas on a replacement.

I will not replace it til spring as I'm going out of the country in February for a month.

I'm looking for a replacement and it seems the EPA requires to replace with like so I need the 2 pre-cats and the main cat. Not sure if the pre-cats need replacing.

any suggestions would be appreciated.

Ray

I've got a magnaflow for my main cat. Idk what you would do for the pre cats though.

The best replacement is a straigt pipe in my opinion, although that may not be legal in your state. What is legal in your state will vary by quite abit.

Under Federal law I believe it is illegal to remove or disable a functioning emission control device. I don't believe it is illegal to remove a broken emissions control device.

1990 Vette exhaust
 

1990 Vette 6MT

I am looking at straight pipes with out the pre-cat and flow master sells one, I live in Las Vegas Nevada, and that version is legal here.

I plan to gut the main cat and see if the pre-cats are good. I like to keep the originals

Reading on the internet indicates the cat's only last to about 70,000 miles, I have 72,000 miles.

Thanks for the reply's

Ray

On my prior '88 I had the front Y replaced with a mandrel-bent 2 1/2" SS Y and the main cat replaced with a hi-flow unit.
It never failed the OH sniffer test, nor their quick visual inspection.

If it's legal in your neck of the woods, eliminate the pre cats entirely.

On my 1988 the front cats were making rattling noise so I had them cut out and straight pipe welded in on the Y section. Now the car *seems* more responsive to the throttle, but that may be a subjective impression from the altered exhaust note. Here in NZ we don't need all the emission controls that the car came with (from California) so no issues with legality.

My neighbour reckons my C4 sounds much better now when I start it up!

First off I have a 1990 corvette with the L98 engine it was purchased new in Cali. I does not have a Engine Family Number EFN, so the cat just has to be legal in your state. In Nevada you do not have to have the Pre-Cats. When I registered the car in Nevada they only checked for the main cat.

Now you need the pre-cats if the main cat requires it. There are mfg's that sell the Y pipe with out pre-cats and there main cat, and the sell it to Nevada.

Here is a URL that discusses that point.

http://www.walkerexhaust.com/support...nverter-basics

I am going to do it myself. I took the exhaust off because the main cat was plugged, looks like the O2 sensor caused the cat to heat up and break up.

I'll put an oscilloscope on the O2 sensor this week end and verify it's bad.

From what I have read you must keep the car original until it no longer passes smog, then you can replace with what is legal in your state.

It takes me about 2 or 3 hours to drop the exhaust, remove the cat from the Y pipe and remove the broken up cat guts, the put it back on.

I am planning to buy a new cat and install it but the mfg of the cat suggest you get it running correctly before putting a new one on.

If you need anymore info we can go out for a beer and talk, or reply back. I am going out of the country later this month for a month, so I will not by the parts till then.

Ray

:iagree:

Do NOT use any pre-cat - period !!!! Not needed with modern CAT.

The store cannot remove emissions equipment unless they are replacing it with an equal or better one BUTTTTT hypothetically, what if I came over for a visit, had a few beers with you and installed a TPIS header set with the Y-pipe to the main cat for testing purposes only? What if I got a call from the wife and had to run off and have not been able to make a trip there to put it back to original?

PS: I thought I heard someone say that it is only illegal when you get caught?

We do not follow C.A.R.B in Nevada if the cat fails you can replace it with any system that is legal in Nevada. My cat failed.

Yeah come over and do a swap, it take 3 + hours depending id the car is from Nevada or any desert location. Cars from where ir rust not sure if I can,

Ray

I looked at that, you have to pass smog to get the plates then you have to go to a smog station to verify mileage every year, you can only drive, I think, 5000 miles a year, I have been thinking about that.

Ray

OK I'll go classic plates, I still have to buy a cat because I have not seen where to buy the Y pipe with out the pre-cats, by itself you always have to buy it as a kit, but it's cheap.

Thanks a lot for the info.

Ray

the best stall converter came with the 86 vette. Its no longer listed in inventory. However, the latter years V6 s-10 had the same converter and can still be had.

Catalytic or torque converter