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Originally Posted by j9FD3s
two things;
1. PJ showed me this years and years ago, but it might work, http://yarchive.net/car/air_induction.html
2. second i've noticed tuning a few cars that going from say 12:1 afr at cruise to 15:1 at cruise "looses power", my gsl-se particularly used to do this when the sensor in the radiator switched it into closed loop, the car would feel torquey, and then when it switched to closed loop, "loose power". |
You are right, an engine does not make quite as much power at 15:1 as it does at 12:1 (unless you are running a tumble head design, which would actually do better at 15:1). However, the BSFC for the engine is much better at 15:1.
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Originally Posted by j9FD3s
but if you think about it backwards, you say it takes X amount of fuel to go 25mph, and @12:1 afr, you have to open the throttle Y percent. when you switch to 15:1 afr, the amount of fuel you need to go 25mph is THE SAME, but the amount of air is bigger so you need to open the accelerator MORE. y+(15:1/12:1)
i hope that makes sense, its easy just to think of the gas pedal as a linear power delivery lever, but with a carb particularly, you can get fuel and air to be separately metered (weather you want it or not!).
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You are correct, and opening the throttle plates increases the engine efficiency even more, so it is a win/win. The typically accepted optimum Lambda is 1.1 (per the Bosch handbook) this works out to about 16.2:1. Believe it or not, the amount of air is more, but the amount of fuel is actually less (considerably). On my engine 12:1 is FILTHY RICH, almost into the black smoke region. Peak power is lean of that for me (about 13.2:1). 12:1 gives better throttle response, so the internal accelerometer senses the jerk of the throttle response and *thinks* that the engine is making more power (I though 12:1 was good until my first dyno session).
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Originally Posted by j9FD3s
A lot of new cars in europe have a "stratified charge" mode, where i think the throttle opens, and its fuel controlled like a diesel. i don't know exactly how you'd implement it on a rotary...
mike
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That would be cool, as the efficiency would be good and the losses across the throttle plates would not exist. We could never get away with that here (NOx emission regulations kill any attempts at combustion-related fuel efficiency gains).