What is effect of removing CAT

[A horse with no name]

Hi...I have a '86 Carrera and and considered taking the CAT off of it. If I do does it effect the running of the car? What about the DME or?

Thanks.
michael

[DCinVA]

Removing the CAT from an 86 may provide for a very small increase in performance, but these cats are very efficient and any increase would probably not be noticable. Small change to exhaust tone (a little louder). Will make you fail emission tests if they are requied in your state. Make sure you install a cat bypass pipe that has a fitting to install the O2 sensor, as this is an input to the DME. Running the car without the O2 sensor will make the car run rich and ruin your gas mileage.

Have fun

Dave

[jlynch1960]

If you live in a well populated place, your neighbors will appreciate it if you leave it on. They convert noxious tailpipe emissions into somewhat less harmful pollutants. Places like LA would be next to uninhabitable without them these days. They do however produce nitrous oxide a major contributor to greenhouse gasses, so if you live in an area surrounded by trees, oddly the environment might be better off without it.

In terms of performance, I put mine back on (PO had removed it) and I think the car is peppier in the low to mid- range with the added back pressure. The marginal gain is probably mostly at the top end, although I think you'd need a dyno comparison to prove that out.

[Jesse16]

Sorry for the blurry photo
My 87's cat with 180k miles was melted inside. Probably 3" on the inlet side and some on the outlet side was gone. My muffler sounded like a maracca from the chunks blown inside. Gone now with a bypass pipe.
The car is noticably louder inside without the cat. Everything gets old and falls apart! If the cat looks OK inside, most folks say its not much of a performance issue to leave it. If you want to hear your radio, best to leave it on, my opinion.

[hcoles]

when removed it lasts longer, install during smog checks, car a bit louder, more power at top end

[mnez]

The worst part is that your car will smell like it was build in the 60's.

[Gustyones]

I pulled mine off my '85 and though i noticed a SMALL change in hp and exhaust note i'm not sure it was worth it due to the extra pollution and the cost of the M&K. If i had to make the decision again i probably would have left it on. Mine was pretty clear though with hardly any build up.

[DCinVA]

If your cat is melted, it has been running to hot, probably a bad O2 sensor.
CATs are expensive to replace with new, but I am sure there are lots of used
ones out there. It seems there is always someone selling a complete exhaust
for a 3.2 for dirt cheap.

[diverdan]

A few years back I lost a couple of cats to some scrappers. I replaced them with after market cats that were fairly small and appeared to have less restriction and they were less than $50.00 each. Performance seemed similar but I'm curious about these cheaper and lighter cats. Anybody know?

Dan

[ben parrish]

Removed the cat on my 86 and it definitely made a difference in power on the top end. I ran it like that for years but finally got tired of the obnoxious smell (ethanol gas) and recently put it back on. Noticed the reduced pull above 5500rpm but living with it. I am thinking about replacing it with a new, smaller, lighter cat.

[KNS]

I didn't notice any change in smell and only a small difference in sound (maybe a little deeper but not really louder). The biggest reason for me was to significantly reduce heat on that side of the engine.