I figure this is the best forum to post this in as it's related to a tuned Corvette and I want to not affect the tune as it relates to this, but if not, the thread can be moved. First of all, I just picked up my first Corvette this weekend as a daily driver--a 2008 A6 base with some mods. Really I'm just looking to use it as a daily driver and nothing much else, such as track time. It came with some mods already, and I'll list them as advertised:

* ARH Long Tube Headers
* Mid America Quad Thunder Mufflers
* Cold air intake with 160 thermostat
* Mild Comp Cam and spring kit
* Ported factory heads

As part of this, no cats, and this had me failing inspection today that is required in our state (I purchased in Texas and drove home--it passed inspection there). I'd be interested in some direction on how to get through this without unloading a load of money. I wasn't banking too much on spending a lot more on the car right now after getting it licensed and registered, but I'm stuck right now on having to come up with a plan.

Are there some reasonably priced cats I could toss in with the given config that wouldn't then force me to have a re-tune / modify a lot more than I want to right now? Is there some other avenue I should look at to just get through inspection for now and looking into things more deeply later? Curious if there are others with similar type setups who have to deal with inspections and needing cats to pass.

Thanks.

 

Why exactly did it fail? Visual lack of cats, emissions or OBD? I don't know what is required in your state.

I would just put the original manifold/cats back on, get through inspection then swap them back. PITA but not that bad.

 

Just visual, no emissions. I had debated putting stock back, though I don't have everything for it right yet. Waiting for one last bit to ship. I'd also have to have someone do it for me--dont have the tools.

 

So you are going to put back the stock CATS? Do you have the stock exhaust manifolds ?
Will you have to do an ODB ( COMPUTER PORT) inspection??

 

Maybe try to get an x-pipe off of a newer vette that has the cats in it. Ask some shops that do inspections to see if it matters how far back the cats are. I don't think it matters in Missouri.

 

In that case I'd probably spend the money on just adding some high flow cats to the current setup and leaving them on. Horsepower loss is next to nothing and it'll help with smell, and you won't have to deal with it again next time you need to pass inspection.

Just my opinion.

 

This is the direction I am heavily leaning towards, especially because I don't want to deal with swapping back and forth every inspection time. I spoke with a local friend who doesn't have cats on a car he likes working on (not a Corvette) and he said if he was to do it again he would never remove them because of how much of an issue it is to get it inspected / to get anyone to look at anything on the car when he needs it. He said the hassle around here isn't worth it.

 

I still have stock everything for the exhaust system minus part of the exhaust pipes that the seller still needs to ship me, but I'm aiming towards not ripping it all and going back to stock (even if just to pass inspection). I don't believe they do any ODB testing in MO.

 

I would do the same. In the Milwaukee WI area, they plug into the OBDII port, no codes, you pass. It is hooked to a central system so the local shop can't cheat, but if you turn off the rear o2 sensors, you pass with no cats.

 

What about a set of gutted cats? I've never heard of anyone actually looking under the car. Most shops think that if you don't have any engine lights on the cats must be there lol

 

The couple I was at actually put it up on a lift and visually inspect that it's there (but basically they just make sure it's there and that's it). I think at this point I'd just assume do it right and put a proper set in and be done with it. While this car does have some tuning done on it, I'm not necessarily stuck on keeping it all pushed to the limits of the parts that are on there--it is basically just my daily driver.

 

Had a muffler shop look it all over today and get me a quote that wasn't too bad, though was told he would likely have to offset them as their size would require a bit of offset where they'd go right behind where the header pipes come together.... they've been doing exhausts for a long time, but I guess don't really deal in Corvettes. Wondering if I should shop around a bit more. They said they could put any cats in there that I come up with, though (think they're just dealing with what local providers have on stock).

Any suggestions on some good high flow cats for 3" pipes that don't break the bank?

 

Give ARH a call and see if you can snag the x pipe with some cats, if you are really in a bind when I get back from Indiana you can put my catted x-pipe on and get it to pass inspection like a mile from my place.

 

Called and they do offer selling just an x-pipe with cats inline for they said about $580 direct from them, though a reseller might be able to get a better price. I just need to determine if it reduces to 2.5" at the end of the x-pipe, or if it stays at 3", which I failed to determine while under it yesterday. I'll need to figure this out, and then see if I can find someone who might offer it cheaper.

This seems the way to go so that I don't go chopping into the existing system and have some better resale of parts if I was to ever remove any of this.

 

the x-pipe itself would not reduce. If you have 2.5 axle back then the reduction would be there. Mine is 3" out the back

 

As best I recall, that's what I thought I saw when I was under it at the muffler shop yesterday (but sadly didn't pay real close attention), but none-the-less, they said they needed to know if it reduced to 2.5" or 3", so it must be some option they have to reduce to 2.5" out of the x-pipe. I think I'll put my phone on a stick with a light tonight and look again to verify, but what you describe is what I think flashes in my mind as what I saw.

 

The output of the X pipe can be 2.5 or 3". 2.5" is common on LS2/3 models. LS7/9 used 3" from the factory.

 

Sorry about the quality, got my phone under the car to try and get video. This shows x-pipe on bottom and mid-pipe on top. I assume this is what a 3" to 2.5" reduction looks like?



If this is a 2.5" reduction on the x-pipe, then I was quoted about $632 to get the x-pipe (2.5" reduction version) with cats plus about $60 shipping. The angle I'm leaning on here is trying to determine if there might be a market to sell my non-cat'd x-pipe after I get this in and recoupe some of the costs. I'd still need to get them on, and I presume they're all supposed to be bolt-on, but I also don't have the tools to do it. I'd hope / assume it shouldn't be difficult to do.

Otherwise, I'm looking at about $600 total for someone to put a couple high-flow magnaflow cats in the existing system and nothing to try and recoupe costs with. Thoughts?

 

Go to the sale section and see if you can find a used one for sale.

Worth a shot!

 

Good call. Found someone with some for sale at a great price... except 3" end to end and no 2.5" reduction.