Quote:
Originally Posted by RustyLugNut
. . . just how relatively low the pressure is in this idealized example. This is because it is idealized ( mean = average of the pressures ) not an actual pressure trace. An actual pressure trace would have peaks that are much higher and plateaus that are much lower. It is also a NET idealized pressure, taking into account the losses of pressure before TDC and after BDC.
Also, it is representative of the power output we as ecommoders strive to reach in our efforts to maximize fuel consumption. Many of the Xprize cars like the Edison VLC, the Aptera and Jack McCornack's Max, need less power than this to cruise at road speeds. But it is certainly a bottom number many of us can strive for with some of our modified cars.
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. . . will look at the BMEP equation and realize that any modifications that maximize BMEP will yield more power at the given rpm. The straightforward solutions of more air, more fuel and optimized ignition timing lead to supercharging, higher flow fuel systems and advanced ignition systems with knock sensor feedback. These and other performance modifications certainly result in increased effective cylinder pressure, but which ones are relevant to the goal of the Ecomodder? We do not want to drive around at nearly full throttle all the time, but as many of us know, this is the throttle setting for a spark ignited gasoline engine that results in the best power output for the lowest fuel input or the lowest BSFC ( Brake-specific-fuel-consumption ).
Since we cannot drive around at heavy load, we pulse and glide to get an "average fuel use" that is considerably less than a partially throttled engine driving the same distance. Engine designers have used cylinder de-activation to achieve the same goal but with varying degrees of success.