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Old 01-17-2009, 08:09 AM   #30 (permalink)
brucepick
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Join Date: Dec 2007
Location: Eastern CT, USA
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Outasight - '00 Honda Insight
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Quote:
Originally Posted by KJSatz View Post
Catalytic converter damage just scared me away from EOC again...would anyone like to explain this more?

:-X
I think it's a bogus reason against EOC.

A modern engine will start burning fuel nearly instantly when started, even when cold. So the air-fuel mixture is burned before it gets to the cat. Even more true for a warm engine. Remember, there's no fuel being injected after engine cut-off so it's not pooling anywhere. Spark and fuel both begin when you spin it up by letting the clutch out.

I think the bogus caution likely dates back to the days of carburetors and points-plugs-condenser ignition setups, where miscellaneous starting issues would end up flooding the engine. If you THEN get the idea to roll it down the driveway and bump start it, all that flooded fuel gets dumped into the cat and would burn there as soon as the cat gets hot enough. Depending on exactly when and how the engine starts, of course. But the cat is designed to get mostly 'combusted' air-fuel mixture, not mostly raw fuel plus air. So the dumped fuel would be bad for the cat.

But that scenario is not likely in your modern computer-controlled car. If the fuel management and ignition are in bad enough shape that raw fuel continually gets to the cat, the car is going to be very tough to drive if you can keep it going at all. In that case, continued operation would likely ruin the cat converter with or without bump starting.
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