What de-cat are you using for your Exige?

[albert]

guys... basically what is a de-cat? And what brand does you use? I heard that 2bular is good but which one is the best and which one are you guys using? Mind to share?

[qball]

De-cat means the catalytic converter has been removed and replaced with a straight pipe.

The straight pipe should have two bungs (i.e. ports) at the beginning (fore) and end (aft) for the O2 sensors. However you may get a check engine light because the 2nd sensor (aft) will not sense that the exhaust has been scrubbed by the non-existant catalytic converter. Some people have not had CELs...

So you may be left with having to find a way to fool the computer to think that the 2nd O2 sensor is OK and not reading faulty. There are a number of solutions here on LT that have been discussed.

De-cating the exhaust will do several things...

1. Might feel some more power, but it may require the right muffler to be combined with it to maximize the benefit
2. It will be MUCH louder
3. You will smell a lot more exhaust fumes (since the catalytic converter is no longer able to scrub the exhaust).
4. You may get a CEL

I have a 2bular exhaust and sport cat. I tried the de-cat pipe for a while and it was too loud and too smelly, and I reverted back to the straight sport cat.

YMMV!

[LordZ]

2bular headers, 2bular decat, 2bular 8" high exit muffler

Smell doesn't bother me, with the 8" it's actually very quiet. It's alot quieter than with my 4" 2bular muffler and my stage2 with cat was.

I think in most states it is also not street legal nor will it pass emissions.

[albert]

I'm thinking of using the Lotus Stage 2 exhaust... Any comment on what catalyst i should use?

[jhnmdahl]

Originally Posted by LordZ

I think in most states it is also not street legal nor will it pass emissions.

It's illegal everywhere (violation of the federal clean air act, among other things), and the fines typically run into the thousands of dollars. No shop will do this for you, as their fines are a lot higher, so if you choose to tinker with your catalytic converter you'll likely have to do it yourself.

John

[bgsterling]

Does a cat really impede performance anymore? Putting social and environmental impacts aside, is there a point to doing it? I remember the early days of catalytic converters and the performance difference with and without a cat was pronounced. It was arguably worth it to pull the cat and then put it back for smog tests. But with modern fuel injection and lessons learned over the last 30+ years of cat development, it doesn't seem like there's much performance to be gained by pulling the cat. Anyone have some real numbers that show the performance difference?

-Brad

[Monsi]

one of the biggest benefits of a decat is the heat it removes from the engine bay

should no longer be able to roast marshmallows over your engine

[Vishus_1]

If the ECU didn't adjust and undo the performance enhancement, I have read many comments on here that suggest decating a supercharged car, in particular, would increase performance - but again the ECU is going to adapt to undo that performance gain. What we are left with as a result of this, is the benefit of reduced heat. That is a good thing all around but then the legal issues become problematic.

A sport cat (like 2bulars high flow cat) may be a good compromise if you should need to replace your stock cat for some reason. But given the cost/benefit of this - I don't fully understand why do it unless:

1.) you live in a state that doesn't require inspections and you think you can get away with it or you don't drive the car on the street - only track.
2.) you have a custom tune - something like CharlieX can do - so undo that learning feature or be special calibrated to your customizations.