I just picked up an 89 IROC, with 80,000 runs good. Tried to get it inspected but the exhaust system failed. Guy said pipe before the cat had a leak and it needed a muffler.. and basically some pipe work. I have a 3 inch exhaust I took off a 92 Z with a 5.7 absolutely NO rust and has a flow master muffler and exhaust tips. I'm wondering if I could use this system. I have the 5.7 TPI bone stock and according to the RPO codes the car has a 2.77 rear end gear (which I plan to change out before spring to maybe a 3.42

stone

 

I'm thinkin' the 89 has a single converter and the 92 is probably dual. It will bolt up to the manifolds but may give your inspector the bends due to the difference even if it passes the sniffer.

 

Yes, the new exhaust has two cat's.. Do I cap off the line on one of the cats going that goes out to the motor ?? (the skinny little tube..both cat's have one)

 

Ok, installed my 3" exhaust on my 89. You were right, it did need a little modification with the extra cat but it worked out. the only thing is it's kinda loud. Sounds like I have a big block 396 under the hood. My goal is to put in a 2 1/2" I read somewhere it would help me out with the back pressure. Stone

 

Stick with the 3" exhaust.

 

I agree LB9GTA stick with the 3" If anything you might change the Flowmaster muffler for something like a Dynomax Super Turbo. As an aside, did you notice any seat of the pants power gain from the dual cats?

 

As "watajob mentioned ,I also don't see how a exhaust system with two cats is going to pass a visual inspection.

 

Hoping the inspector doesn't notice?

 

We'll it did pass.. From what I understand the newer third gens came with dual cats, but don't hold me to that. He looked under there, said cats look ok, hooked up the machine slapped the inspection sticker and I was gone.. Not going to worry about it, just glad to be driving my car! Stone

 

Yeah, I'd be sure to uses that guy all the time with your smog testing.
Nice to hear you passed though. Have fun with your new car.
Your saying you have a 9 bolt so a new gear ratio from 2.77 to 3.45 and a posi.(if you don't have one already) will make a huge difference,you will love them.
Here's a link to a thread concerning the 9 bolt = https://www.thirdgen.org/forums/faq-...now-about.html

 

I have the 3" Flowmaster 80's Series System with dual cats on my 92 Z28 L98 and it sounds awesome like a Monster that's how I always wanted it. BEAST. if I wanted it to be not so loud and just moderate I would have kept it stock.

 

I'm running a Hooker Aerochamber exhaust. It's mellow just cruising around but roars wen you stand on it!

 

89 was the first year for dual cats. It was part part the G92 OPTION with 240hp. Also the only G92 cars with T-Tops.

 

Ok I must just be missing something.. My car is an 89, and 89 was the first year for dual cats and so my car shouldn't pass because "___________________" ? Please fill in the blank, just the blank..

As far as the car sounding like a monster, dude you're right ON. I have the exact same thing you do ( I think, says 80 series dual cats 3") I'm getting use to it, getting on it is fun, like you said... sounds like a beast.

Stone

 

Some people need to do some more reshearch. If you have cat(s) on the car it will pass.

 

As stated above, 89-92 N10 is the dual cat option on 350 tpi auto and tpi 305 5spd cars with certain performance options.

FYI: backpressure is bad