50 4Ever

As said before, no-cats is your problem. Hi-flow cats are fine for a while, mine burned out in 6-months.

Dan_the_C5_Man

Could you please share the details? Type of headers, type of CATs (some vendors supply a mid quality or high quality versions)?

What mods do you have (high lift cam, any boost or other power-adders)?

Type of driving (road racing, street driving, drag racing)?

Any special fuels used? Tune rich or lean?

Thanks!

ZedOhSick

I bolted cats on and it completely fixed the fume smell. No noticeable loss in power but a slightly more muffled sound (to be expected. Let's hope my cats last longer than 6 months...I am also curious as to your driving and mods that would cause it to burn out so fast.

Michael_D

I have seen a lot of tune files with cat protection disabled. Bad idea if you have cats.

50 4Ever

Kooks 1 7/8" LT Headers, I think the Hi-flow CATS came from Kooks,Mild Cam, Street and road racing - no drag racing. With headers and slightly bigger cam and hi-flow cats it was putting down 545 RWHP (same RWHP as a stock ZR1 on this dyno). Because I had to pass smog I put in a smog cam from Synergy, put back on the stock exhaust manifolds and stock CATS. Now it puts down 525 RWHP.

No special fuels, forgot what the air/fuel ratio is, but it is not lean or rich. The A/F is pretty much the same across the graph.

Dan_the_C5_Man

Thanks for the feedback, same exhaust on mine, but stock cam - will probably end up right around 500 RWHP. Fingers crossed they will hold up.

I should have asked during the first round - how did you know they went bad? Gas smell, clogged or came apart and landed in the mufflers?

C5Dobie

I ran catless JBA LTs on my G8 GT w/ a "baby" DOD delete cam, it had a gas smell seemed worse in warmer weather, but at idle it would still pass a sniffer test so long as you didn't touch the throttle (even the slightest pressure would fail emissions) - now a legit inspection station would still be able to smell the fumes and if they looked underneath would notice no cats, so you'd still need to "know someone" or slip a $50 to get a sticker.

Only reason I mentioned this is because that car was tuned such that it would pass emissions @ idle, was running a relatively mild cam, but STILL has the gas smell....I imagine not as bad as what you describe, but I don't think there's any way you can completely eliminate it especially running no cats. You're car would smell even with the stock cam and no cats.

Hi-flow cats will tone the smell down but with such a lopey cam I think you're still going to have that odor.

Nature of the "beast" -(no pun intended, but intended)