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Do wankel engines use 'acceleration enrichment' like piston engines?
When you floor it, the engine computer injects a whole lot of gas in an effort to cool the incoming air. A recent article in an car magazine test a Dakota pickup, at full throttle the air to fuel was 10.9:1 super rich!
I thought that somewhere Mazda said that the wankel runs lean all the time to keep the heat up and emissions low.
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I think you may have confused something there. Unless there is some odd exception, ECUs on piston engines are not going to dump fuel in an effort to cool incoming air, that is simply not a good way of doing things. You might cool the incoming air slightly, but you'll mess up the A/F ratio so much that you'd make things worse than better (not even considering all of the wasted fuel, and loading the cats with an overrich exhaust). The only time that I can think of that you'll see an ECU dump fuel like that is on factory FI applications, and it will only happen if the ECU is reading an overboost situation, and is scrambling to save the engine.
In most cases, when someone "stomps" on the accelerator, the fuel system isn't quite fast enough in reacting to the sudden increase in airflow. There is a little lag time when the engine will actually run lean, but it's only for a very short time. To compensate for this, most ECUs will add extra fuel for a short moment if it senses a drastic throttle increase (as in someone stompin' on the gas), which might be what you heard of as "acceleration enrichment". Some carbs were even designed to do the same thing. But it is only for a brief moment, to cover that lag until the fuel system can catch up (much less than a second).
As far as the Dakota at Wide Open Throttle, most ECUs bypass certain functions at WOT (O2 sensor, some EGR functions. etc.). Still, the Dakota at WOT running 10.9:1 is not good at all. Either there was something wrong with their measurement, or Dodge dorked up their ECU tuning.