I know that, except I think it was Sulavaca.
I said that above
[quote=“redwagon”]If you then remove the cats you have to completely retune the car to run clean without them. A well-tuned car can pass most emissions standards without a cat, but ‘well-tuned’ means individual custom tune and no manufacturer can afford to do that for every car off the line. DIY requires specialist tuning software and a wideband O2 sensor at the least. Very few carburetted cars are catted, so you have to modify the maps in the fuel injection computer.
AFAIK there is no requirement in Taiwan to leave all the emissions equipment as-is. If you personally take a car in for test that has a loud exhaust and emits black smoke you will probably fail. If the right mechanic takes it in, it could easily pass. A lot of people drive catless 364 days a year and refit the stock exhaust for testing. The testing centers are under instructions these days to make life hard for modified cars, so going in with a huge aftermarket muffler is not going to go well.
BTW, although current standards require the cars to be certified with emissions tested under load, the inspections of used cars only check emissions at idle, since none of the testing stations, and probably not even the DMV stations, have a rolling road. With a healthy car, in theory you could remove the cats and still pass inspection as long as the muffler looks and sounds stock. The idle mixture on modern injected cars is set to stoichiometric and the cats usually don’t light at idle as there’s not enough energy in the exhaust gas, so the cats are doing nothing at idle.[/quote]
The crux of the matter, and thanks for that full explanation. IOW you can probably get away with just about anything, but doing it properly isn’t likely to be a practical DIY job (and probably still less a practical “black hand” job).
Of course if you say that I believe you, but IF the system is using feedback from an O2 sensor I don’t quite see why it can’t keep itself clean whether there’s a cat there or not. I suppose you lose too much power running that close to stochiometric?
I think I’ve read something somewhere about making a DIY “EGA” using the oxygen sensor from a scrap car (doesn’t actually analyse the gases of course, just gives you a null indicator of stochiometry). Wouldn’t get you round the computer re-mapping requirement, but it might be a very useful aid to tuning a non-cat car or motorcycle. I’ll look it up. Might be a vacation project, though probably not.
If there is this wouldn’t have been an appropriate question for it, since I’m inviting comment on whether 2-stroke oil would be useful as an UCL for an uncatalysed 4-stroke engine, as apparently found in Sandman’s Sentra.
A priori it seems to me it would, but I’ve never heard of it being done and there might be a good reason that it isn’t.
Edit: I originally considered suggesting it on a forum for those Chinese copies of prewar sidevalve BMW’s, which apparently break a lot, but since I’m never likely to own one of them, I couldn’t be bothered to register. They’d probably just have ignored it anyway. Goddam pseudo-Nazi’s.
