This is the reason I don't like short ram intakes. I think they can sound really good, and they make good power on the dyno when the hood is up. They even make good power when you are moving on the freeway. The thing that happens around town though is when you are sitting at a stop light idling, and the cooling fan is running, and the engine is heat soaking, the intake air temps are rising. When you start moving again, the air flow cools down a bit pretty quick. What most people don't realize is that when you are sitting idling and the air temps are rising, the computer is richening up the mixture and retarding the timing. This is prevent the engine from getting hot and helps reduce oxides of nitrogen. When the computer starts seeing air temps going back down, it does not lean out the mixture or advance the timing immediately, it can take a minute of so. You could eliminate this algorithm if you could reverse engineer the firmware but few people are able to this. At Dinan Engineering we were able to eliminate this rich mixture/retarded timing in race Mini's we tuned. What would happen is when there was a yellow flag and everyone was slowed, the timing would get retarded and the fuel mixture would richen. Ours did not do that so when the race started up again, our cars were able to pull on the other ones because they had considerably more power, if only for 30 seconds or so. Definately enough to pass a few cars.
A cold air intake pulls the air from outside the engine compartment so it doesn't have this problem. Most of the gains I have seen on short rams are hood-open dyno runs which do not simulate the real world. It's called bench racing. Just my .02¢
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