few questions - reversing a cat delete
 

hey guys

I just grabbed a 2011 grand sport

It has a vararam intake , Nick Williams 102 TB, fast LSXR, American racing headers, 3 inch pipes (cat delete) and a titan 1 cam

The driving in traffic is UNBEARABLE , the gas smell is literally making me sick, and anyone who sits in the car with me cant take it either

Few questions

1. do I need 3 inch cats now since the pipes commecting to the headers were 3 inches?
2. will I need to get the engine retuned ?
3. how much power will I lose?
4. would high flow cats fix the problem or will they still be spitting out unburned fuel?

Car is rated now at 480 Hp to the wheels (approx. 560 to crank) , what kind of losses do you tink I would see? I was told it would mostly affect the upper RPM range, is this true?

I rarely go above 4000 rpms anyways

Thanks a lot guys, pls help me fix this issue, the car is almost undriveable

1. 3" aftermarket high flow cats.
2. yes, I would because of your mods.
3. None , may gain with better tune.
4. Yes, the tune will help also.

Do you have the air on circulate or is it being brought in from outside? I've had several cat-less vehicles and never had issues with smell.

Cats will fix your issue but it sounds like it needs
tuned correctly as it is
i would use standard Zo6 cats as they are 3” and
you never go above 4000 rpm they will last longer and
perform, for your application, better than high flow cats
fwiw it’s ok to twist the rpms up the LS platform handles
that duty easily
i

Have to go with the tune question. You have an air/fuel mixture issue and the engine is running far too rich.

Do you mean exhaust gas or gas fumes from the fuel tank, if it’s from the tank GM will fix it under warranty there’s a TSB on this.

Thanks alot guys

I'll keep an eye out for z06 cats

I was told by a shop the magnaflows wont last , I find it hard to believe as they are a reputable company

Any other brands worth looking into ?

My last car was cammed and cat delete. Only time I smelled it was cold start in the garage if I didn’t pull out right away

I'd just get the catted mid/X-pipe from American Racing Headers, should be a just a bolt in affair.

Unless you have a bad tune I don't think the gas smell is related to your lack of cats. I did a full 3" exhaust with cat delete. The exhaust smells different but does not have a unburned gas smell. The fuel tanks are known for leaking from a plastic fitting on the top of the tanks. I found this info by doing a search on this site. Best of luck on a resolution.

I’d love to hear what you come up with. I’ve got the same problem on a similar build. The cats were deleted on mine already when I bought the car. Mine is a 2005, so not eligible for the fuel tank fix, lucky me. I could live with the smell but the girlfriend doesn’t even want to ride in it because of it. If the cats fix the problem for you I’ll try the same.

thanks again guys, its definitely because of the cats , the cats are there because they re-burn the exhaust gasses and make them less toxic, I think having a cam makes things worse.

I have a chance to get a pair of C7 z06 cats , does anyone know if they will work ?

Im assuming they would be 3 inch also same as the c6?

Thanks

The smell can be much improved if not eliminated with proper tuning. A cam change requires changes to the injection timing or it can smell a varying amount depending on the cam specs.

thanks canuck, im not trying to be rude, I d appreciate all replies, but you cannot "tune out" the gases coming from the engine

You could probably get the car leaned out wen its idling, and have less gases but that's really it

If you call a performance shop and ask them to tune out the smell coming from the cat delete, they will tell you flat out theres nothing they can do

Do you know who tuned the car and ate they a good tuner? What the guysor ladies are saying sounds like the car is running super rich which is what our sounds like. You may want to have a good tuner tune the car and yes that will clear up the smell or you may have something going on with a front O2 sensor but haven't thrown a CEL light yet

I would not think a C7 cat would work on your car
starting in 2012 Corvette went to quad cats over the
dual cats your car has

I am not trying to be rude either, but you are dead wrong on this. You are talking to the wrong shops I guess. The injection timing is setup for the stock cam. When you change the cam events, you change when fuel is injected in relation to the valves. If you are spraying fuel when the exhaust valve is open, it will stink like hell. I have been there. My car smelled bad when I removed my cats. With tuning (which I do myself) I all but eliminated the smell, and not by leaning it out either. A lot of tuners wont take the time, or don't understand EOIT tuning. Find one that does.

the car has been tuned multiple times over the years for all the aftermarket parts that have been put on, first tune was for headers and intake, then the lsxr fast , then the cam, then for the nick Williams 102mm TB

I then personally had the car tuned one last time by the shop before I drove it home, its getting 25-26 mpg's on the highway , with 570hp at the crank, and it runs smooth and silk throughout all rpm ranges

I personally don't feel its the tune, I think its the combination of the cam and cat delete causing the odour.


Thanks , and I just asked him about that, I have a feeling they are the secondary cats hes selling, and I think they are 2 3/4 not 3 inches but im awaiting for him to measure them

I might end up going with a 3 inch flowmasters or magnaflows, they can be had cheap with a warrantee I just hope they are good quality and last

The car is not running on the stock tune, its been tuned multiple times throughout the years by the same shop each time a mod was done.

I would feel very confident to say BOLDLY that there isn't any shop in Canada that would promise me they can remove the smell from the cat delete if I bring the car to them for tuning.

If you can find one please send me their info id really be interested to speak to them.

A tune here runs at least $500-$600 and for that price I can probably have some cats installed including the cost of parts.

I am I Canada also and tune my own car. I don't
know what tuners will do it right. I can tell you from experience that cats or no cats, if the EOIT is not tuned for the cam, the car is not running at its optimum performance. Adjusting that not only cleaned up the smell but my car never ran better.
Good luck with whatever you choose to do.

no it comes in from the outside, only when im stopped at lights or starting it up in the garage , other then that you cant smell anything

its not really a raw gas smell, its just a bad smell that you know isn't good for you , its very bothersome for me, for the extra 4-5 horsepower id rather have it fixed

yep the garage is where its most noticeable , and stopped at lights

great idea, im having a hard time finding it though, I can only find the whole set up from headers back, ill try to call them tomorrow

ill let u know forsure, this is my number 1 priority now , so shouldn't be too long