I posted this in the Great Lakes region section, but I know some folks don't venture there as often, so I thought I'd throw it out here. It's an Ohio EPA regulation question.

've got an 90/L98 with an exhaust system that I am planning to replace. It has the two precats on the front Y pipe, then the main center cat. Can I eliminate the front two precats, keep the main center cat and remain "legal"? I no longer have to go through E-Check (Ohio's emission test), but I don't trust that it won't come back. I'm looking to save $$ where I can, pick up power and not cause my hearing to go bad. I've heard some conflicting comments regarding what removing the precats will do to the sound. I'm not looking for louder. I had a local exhaust shop looking into whether or not they could replace the sytem without the precats but I've not heard back yet. I've also read the Ohio EPA regulations, which pretty much states you can't alter the existing system. I can't believe with today's technology that it would matter as long as I keep the main cat.

 

You can pass a sniffer in 49 states without the precats, but in states with visual inspections, its hard to say. Some are **** about modifying factory emissions systems.

It will be louder, just not terribly louder. Shouldnt be to the point of causing headaches.

 

1) You didn't mention what you're going to do with the rear section. That will make a difference. (In general, think of your car as having 3 mufflers. Front cats, main cat, and rear mufflers. Removal each element will make your system progressively louder). If you open up the rear section (new muffler or no muffler), dropping the front cats will be getting fairly loud!

2) Technically, you're not supposed to change the configuration of your emissions. So, technically, you'll be illegal. Practically, no one will care -- including repair shops.

3) Do a search on precats and GREGGPENN. I've done this recently and had some issues with precat removal. You may get popping during warm-up and you may not like it.

4) Ecklers sells a 1 cat replacement that they claim is 49-state legal to replace the 3-cat setup. Call them and ask if this is really true for your state. I'd ask how this works since you're not suppose to change the config of emissions. Their claim is the main cat is a two-stage converter that replaces the combined function of the factory front/rear converters.

5) If you're replacing the front "Y", dropping the front cats, and don't use option #4, consider a 2.5" bolt-up stainless upgrade. (Factory is 2.25"). PM me and I'll point you in the right direction on where this is sold. I bought one!

6) I agree with your last statement. Newer car computers are depending on existence and proper function of the converters. The cars won't easily run without them. My muffler shop thinks this will eliminate the need for inspections. That might be why your state ceased doing them. That's also one reason why no one will care. Also, 84/85 cars didn't have front converters either. So, you really have to know your vettes to spot one without factory precats!

 

Local muffler shop installed new catless front pipe for me here in Michigan last summer. I also had them install a high flow main cat, rear Y pipe with crossover and Magnaflow mufflers. Sounds sweet and they felt they were NOT breaking any federal laws. Go for it!

 

Thanks for the replies. My motivation is due to the precats failing (driver's side rattles periodically) and very bad resonance in the cabin. When I had the system checked, the exhaust guys quickly pointed to the "after market" main cat and said most of my resonance was coming from there. I may also have an engine tune issue, which I'm trying to work into my schedule to have it checked, before I make any exhaust change. Plus I wouldn't mind dressing it up a bit with some new mufflers.

I've got a lead on a system coming off of a 96 LT4 that I believe I can make fit, which sounds very attractive. If that doesn't pan out, I will most likely go with either a full Magnaflow system from the manifold back, new high flow Magnaflow main cat and/or put an OEM replacement front Y w/precats and Magnaflow cat back. From what I've read this seems to be the best solution for what I'm looking for.

 

How much did you pay to have that done compared to the vendors that sell those? I want to get the stainless steel one for now because I feel I'm lacking in power and my fronty y pipe seems to be getting clogged.

 

I have a 90 six speed. I bought the precat eliminator y pipe and main converter from ebay. I installed it myself with no problem. I was changing the shifter to a hurst so I had the old pipes off anyway. I also have a magnaflow catback and the whole system is quieter than muffler eliminators which I removed. Its a much throatier sound. I actually bought another one for a friend who has since sold his car. If you want a deal on a brand new set, pm me. I live 40 minutes from Rochester.

 

I removed the precats on my 91 and installed a catco hi flo main cat. Passed emmisions in Tex. I did open up my dummy tailpipes on my stock mufflers at the same time and it did make everything louder. Good luck with yours.

 

I bought the front and rear Ys from different Forum members for about $50 each. They had never been used. I bought the cat and Magnaflow mufflers (the aluminum coated ones) from www.corvettecentral.com
You can go to their web site to get the price. I also had the shop install a new O2 sensor that I got from a GM dealer. I then went back to Corvette Central and bought chrome ZR-1 tips for around $100. The system was perfect!