Quote:
Originally Posted by zerodameaon
What so he can waste gas? Sitting in line revving your engine does not help and only calls attention to yourself.
Also unless your best friend will hook you up buying a cat is cheaper and well, not illegal.
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No, just let it chill at a fast idle, if it's possible and not obvious.. Don't be all fast and the furious.
Nothing to do with wasting gas. If you don't understand why a hot motor is considerably more likely to have good numbers, there's no helping you.... but I'll try.
When your motor is cold (idle is quite cold, even if it's "warmed up") the combustion is not as complete - this is why we have all these systems that kick in at idle to help with emissions. Oil burns and makes gummy stuff that will burn when you do have to get rpms up for the tests - this is why a car that burns oil will sit and idle and not smoke, but when you touch the throttle it makes clouds - hopefully his car's not that bad obviously, but even a perfect engine MUST burn oil, by design, because it's what lubricates the rings. But the gas as well, and everything sitting around moving slowly in the egr passages and such - if the cat's not so good, you don't want it getting cold, that's why we have a pair valve - to keep it "cooking". You want to go in there with a blisteringly hot engine that's had all the crud burnt out of it right up until the last moment, and a cat that's super hot so it's actually converting like it should be.
Basically your motor slowly fills with coal when it runs cold. Coal is dirty. Dirty fails tests. When it's hot it can keep up with it's own waste production, as well as simply producing less of it. This is also what seafoam helps dissolve, so it can be burnt the rest of the way and blasted out.
Now, I'm half expecting something about how that's what valve seals and piston rings take care of, and they should be replaced.... But if you're not volunteering to pay for his oem rebuild, that's irrelevant. This is an old motor that's probably out of tolerances in many ways. We wouldn't be discussing this at all if it was a perfect situation with a car that had no trouble with this test.