cat delete? Options

[Tyler]

Iv noticed a lot of you guys put just a little something on for exhaust just to open it up and let the car breathe a bit better but it seems everyone is doing cat back. Am I the only one that wants to take out the cat and go strait back from the headers to a muffler?

[silet]

Deleting a catalytic converter these days causes emissions problems with car computers being so finicky.

On the other hand, you have to know what you're doing when deleting a cat. You have to have a purpose and goal. If your goal is more horsepower, then removing the cat alone will do nothing towards that objective.

Modern catalytic converters do not restrict flow as much as people think. The exhaust resonator and muffler do a lot more to restrict flow and the intake resonator too.

So in conclusion, if you want more HP removing the cat is not the way to go...

[Bobzilla]

Agreed. Even deleting the cat and replacing with a header (singular, we only have one, not multiple headers) you can expect to gain about 2-3hp as has been shown on multiple dyno's over the years. Biggest improvement with the XD chassis in regard to exhaust is the muffler. The exhaust pipe feeding the muffler is ~2" id. The outlet of the muffler is under 1-7/8" ID. Removing the muffler frees up more power than hacking off your cat and dealing with a CEL on for years to come and not being able to pass emissions in your state (if required)

[Tyler]

Oh ok. And no I don't have emission testing. And I didn't realize there was such a small amount of gain with cutting it off.

Also iv read there is two cats on our cars is this correct?

[silet]

yes, two cats.

[only1db]

yes the first cat i welded (casted) into the exhaust manifold while the other is down stream...the 2nd cat you can remove without any ill effect or cel.

[korea_senpai]

Are there not 2 O2 sensors?

[bhorste]

Are there not 2 O2 sensors?

There are... the first is before the first cat and the second is after (or between cats).

[korea_senpai]

I don't see a problem with deleting the cat, shouldn't throw a CEL but the only thing its going to do is probably make your car annoyingly louder. I deleted my catalytic converter on my RX7 and its obnoxiously loud.

[bhorste]

I don't see a problem with deleting the cat, shouldn't throw a CEL but the only thing its going to do is probably make your car annoyingly louder. I deleted my catalytic converter on my RX7 and its obnoxiously loud.

Wankels are notoriously loud anyway. I have a friend that had a 2nd gen RX7 (I want to say ~'89) and it was pretty loud. Granted, it had a rebuilt engine and probably not much in the way of emissions control, but it was loud. I doubt removing the 2nd cat on one of our cars would really add that much extra noise, since you've still got a resonator and the muffler after it, plus a couple of bends. What it *will* do is make it more likely that you won't pass emissions (if required) and it might affect your 2nd 02 sensor readings.

[korea_senpai]

So we're talking about deleting one or both?

[Tyler]

I was considering removing both the cats and resonator to lesson the restriction. But if it does make that much difference ill leave the first so I don't have to look at the cel lol