Quote:
Originally Posted by Hujan
Where are you deducing that information from the video? The cold-start cycle is designed to pump hot gas through the exhaust system in order to warm up the catalytic converters and therefore reduce emissions. It does so by leaning out the fuel mixture (more air than gasoline) so the EGTs are high and pollutant content low.
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The external air pump flows fresh air into the exhaust ports and this creates more complete burning/after-burning of the rich cold start mixture and adds heat into the exhaust stream. Not only does this help warm-up the cats, but it also keeps unburned fuel out of them. The "leaning" of the mixture is post-combustion chamber so that the car can still run well cold.