Dane,

I didn't find the right thread size because I had a burning need for an inspection and my cobbled together straight pipe setup was leaking (my welds just weren't the best). I gave up and just got a new Y pipe with cats off ebay. I think the brand was Davico.

In case anyone finds this post by searching for Davico, the setup works. It comes with much smaller cats than the original and the passenger cat is a hair away from the driveshaft, even with some muscling, but it works.

Charlie V

I tried it on mine some months ago. Tried and tried and I never could get it to work. I found some neat little things on Amazon that had a piece of the catalytic converter honeycomb in the tip that is similar other than that one difference, it might be worth a try if it is 18mm like the O2.

Bump....

O2 Simulator Mini Cat Cel Fix best oxygen sensor simulator made.

Eyeballing these if I ever go the header route....

That's really interesting. I haven't looked back at my old posts but a problem I had with hollowing the cats was that it made the truck sound like a glass bottle rolling down the driveway but that may have been because of the shape of the cat chamber and the thinness of the walls when compared to normal exhaust pipe. Maybe if you had an actual pipe instead on the cat chamber the noise would be less odd.

I've always understood that you need a certain amount of catalyst to burn/convert the remaining fuel and gasses, but maybe those little suckers will work.

I don't think the post cat sensors do anything other than keep you ses light off.

Yeah, post cat are just cat efficiency. Pre-cat are for engine management.

Those little mini cats take the defouler thing a step further. I'd assume they would work because the volume of gasses going to the sensor would be reduced...you're not trying to catalyze everything as you are with a conventional cat.

I'd try them on my 330i...Chinese headers deleted the cats but the o2 bungs were so close to the body of the car I just relocated the post cat sensors to the engine bay, so defoulers won't fit. Pre-cat still fit.

I'll probably not get headers for the D2 straight away, but when I do I'll try these thing out. If someone with headers already wants to give 'em a try, please report back.

These are pretty sweet but dang $50 a piece is a bit steep for me. Anyone found anything equivalent for a little less?

Saw a recent reply to this on my email; the thread is a m18x1.5 for the o2 sensor bungs.

Also, the part number for the foulers you're talking about is 42002 at autozone for about 3$ a set of two.

I ended up just rerouing both down pipes into a single catalytic converter to keep the heat away from my driveshaft and for my 3 linked front end.