No cats and running too rich!!

maimikid · 06-02-2005, 08:50 PM

My '03 boxster has a lot of mods (as you can see in the picture, even a turbo front, lowered springs, different shocks, wheels, wing, etc etc) But it is in engine work where today I hit a problem! I had replaced the secondary cats on the car with bypass pipes from Fabspeed. And then today had headers put on, replacing the primary cats. Also put a high performance air intake on. Alread have a sport exhaust. So the car is running no cats, but from the moment I left the shop, it is running SO RICH that at idle it often just dies, and under 3000 rpm jerks and jumps, then only goes into smooth mode after 3K. Black smoke is billowing out the back, at slow speeds and when I hit the gas. What can I do? won't the chip adjust to the no cats (I love the sound, raw, and very aggressive - this is pretty personal, you are either going to hate or love no cats) - maybe it is the way the O2 sensors are placed? Should they be in the pipes?
thanks for any advice on this!
miami kid

AFJuvat · 06-03-2005, 05:54 PM

Let me guess, you have a check engine light flashing at you as well.

Therefore, the 1st o2 sensor is reading the fuel\air mixture and reporting it to the DME

The second set of o2 sensors that were behind the cat are reporting no change in emissions (it is inferring that the catalysts are not working)

As a result, your DME (the brain) is trying to over-correct the mixture based upon the input from the sensors. But since no corrections seem to be working, the DME keeps richening and leaning out the car.

Before you ask, no, you can't just remove the oxygen sensors. That will force the car into a "limp home" mode

Put the cats back on. Or get some sport cats (http://www.fvd.com) and put them in.

AFJuvat

maimikid · 06-05-2005, 02:52 PM

Yes, you were right. Trying to run no cats was not the wisest move. Instead, I kept the headers on, eliminating the primary cats, and then swapped my secondary bypass pipes for a set of pipes with high-flow cats. The sound is not as ferocious as with no cats, but it is also behaving well now, and running strong. The tech who put them in, also extended the 02 sensors so the check engine light doesn't come on, and the computer on board seems to have adapted very nicely to the new setup.

Thanks for the answer and advice. I was a little too eager to do a wholesale modification....

Ferrara_racing · 06-06-2005, 06:06 PM

I would check back with Fabspeed for the setup they suggest. It's a great looking car, I hope you get it straight.