View Full Version : Question about CATS

05-07-2012, 09:56 PM
Yeah Cats not Vats and not the kind you pet :)

Anyone run a set of high flow cats on their swap. I know it might seem silly for a car built in 1966 but I guess I'm just too used to not smelling the engine in new cars and mine kinda stinks.

Maybe I need to take a trip back to my tuner to see if its too rich?

If anyone has done it do you just find a universal model that fits your system and install them without doing anything else? My rear o2's were already deleted from the tune and my harness doesn't have provisions for them so hopefully those aren't required.

Let me know your thoughts.

05-08-2012, 06:21 AM
I have the same issue, stinky exhaust. I was contemplating the cat attempt as well. I know that Magnaflow makes a wide range of cats in many various dimensions. Some have air fittings and some do not. Some also have O2 bungs. Not sure about the rear O2.

05-08-2012, 07:03 PM
Im not running high flow cats, but i am running cats on my chevelle with no rear 02's and no smell. Running F-body manifolds and cats.

05-09-2012, 06:15 PM
I may have to give this a try...

05-10-2012, 06:43 AM
Please post your results.

05-10-2012, 06:22 PM
It probably won't happen any time soon but if it does I will post up what I did and how it turned out.

05-10-2012, 09:38 PM
Try some different brand fuels. On my DD that has a cat-ectomy some brands stink more than others. BP being the worst of them

I don't run catcons on my Cutlass with a LY6, don't notice any smell even with the top down.

Way I see it hope some treehugger in a Prius (or even better, a coal-powered Chevy Volt) gets stuck behind me and chokes on the fumes they are responsible for creating.

05-10-2012, 10:03 PM
I would never of expected to smell exhuast of a EFI LS swap.. Are your engines high milage of modified but without a dyno tune that can explain the bad smell?

05-11-2012, 06:45 AM
Mine has not been on the dyno yet. The tune is a canned program for the LQ with the supercharger. Runs well, just has the rich smell all of the time.

05-11-2012, 07:35 AM
I did a cats vs. no cats on the engine dyno. It was on a H/C/I 500hp 6.0L with a Dynatech f-body 1 3/4" headers into dual cats and then y-pipe into a single 3".

Gained 4 fwhp by taking off the cats..... Not woth it, not for gas smell that comes with it especially!!!

05-11-2012, 01:50 PM
A lot of the gas smell can be tuned out without having to run lean. I have run without cats on my car before and the only time I got a gas smell was after start up because I have the after start enrichment too high I think.

Also, the rear O2 are simply there to tell the computer that the cats are working. They are for emissions only. It will not affect A/F ratio.

05-11-2012, 07:55 PM
All good info thanks! Mine was tuned on a dyno so I would have to ask the tuner about working on it some more. But for 4hp difference if it completely solves the smell problem I think its a good thing to have.

05-11-2012, 11:24 PM
If I remember correctly advancing the timing a bit in the areas of idle and cruise will help. You just have to pay attention to knock. If you start to get ANY pull the timing back a degree or two.

05-12-2012, 10:06 AM
Bought a set of these to help get rid of the smell; unfortunately I won't be able to give details on how I like it for a while; still putting car back together. But these seem to be the best price: