|
Efficiency is best at lower RPM and higher loads, for normal passenger car designs.
When the effective compression (actual compression in the cylinder when combustion occurs) is highest you get the most power (without full load enrichment). Higher RPM reduces the efficiency due to reciprocation and friction losses.
Mileage would be fantastic if you could use a 20 HP engine to produce 10 HP to maintain a certain speed, but your performance would be pitiful.
The current trend is towards smaller engines that still have enough power reserve for decent performance. This is one reason forced induction may be the best solution, because it provides a reserve of power in a smaller engine.
Alfa Romeo built a Grand Prix engine in 1950 that produced 390 HP from 90 cubic inches, but it only got 2 MPG in racing trim. Modern technology allows the best of both worlds with variable valve timing and precision fuel and ignition controls and ultra high pressure fuel injection.
regards
Mech
|