Quote:
Originally Posted by crystalworks
From my experience tuning an aftermarket EMS, they run pretty rich during and right after startup to help the car start and idle easier during open loop until the cats and emissions stuff triggers closed loop running. So I'm guessing that's the reason it's possible under just the right circumstances.
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That's why I tell people to wait at least 5 minutes before shutting down their BMW when the temps get below freezing. 5 minutes of running should heat up the 02 sensors and you would be in the closed loop where the fuel system can be adjusted by the computer. When the engine is in open loop it is just operating base on the ect (engine coolant temp) and the ambient air temp with a predetermined fuel map. This fuel map provides for a very rich mixture to prevent the engine from stalling on very cold days. Back before computer controlled electronic fuel injection (BC) the rich condition was provided by a choke on the carb. The choke would restrict the amount of air entering the carb so the mixture will be a lot richer.
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