Originally posted by: yelo333
Originally posted by: Zenmervolt
Originally posted by: PandaBear
Engine's efficiency band is usually at 40-50% maximum rpm (redline) and that means usually WOT is not as efficient than having your pedal 40-60% down. Your engine has to retard timing and run richer when you WOT, and the engine is usually tuned to the most commonly used band, around 1500rpm to 3500rpm.
Once again, peak power efficiency is
NOT synonymous with peak mileage efficiency.
WOT allows an engine to operate most efficiently through the reduction of pumping losses. An engine with a restricted throttle opening is literally throwing efficiency away. Diesel engines lack a throttle butterfly, instead of controlling a butterfly valve, the accelerator of a Diesel engine modulates the injector pulse duration. The big efficiency gain of a Diesel engine is largely due to the fact that it has vastly lower pumping loss when compared to a gasoline engine. Yes, Diesel fuel has a higher energy content, but not enough higher to account for the majority of the efficiency advantage that a diesel enjoys.
Again, the most efficient real-world scenario is to use 75% to 90% throttle and upshift as soon as is possible without lugging the engine.
ZV
Perhaps my car (MT 07 Civic LX) is an exception to your general rule of 75% to 90% throttle w/out lugging?
1) It has this
i-VTEC thing, which allows the throttle butterfly to remain almost all the way open during low load by delaying the closure of the intake valves until the piston is a good way into the upstroke phase. (did I say this right?)
2) It has a DBW throttle, which maps throttle in a nonlinear way, to make the engine feel more responsive. In the real world, it means I get minimal additional throttle response by going WOT compared to when the throttle is halfway down. If I were following your suggestion, I would be shooting for 75-90% throttle, but not necessarily 3/4 of the way down, right?
I'm thinking that these two things would mean the following if I'm trying to achieve maximum gas mileage:
Get the economy mode to kick in ASAP, and give it only as much throttle as will keep it there. I can feel it change over, since there is a (very) slight jerk and change in engine pitch. Still shift at the lowest speed that doesn't cause lugging.
In practice, there it takes such a small amount of throttle to get it back out of economy mode that it takes me about as long as it would for a fully loaded semi to get up to speed when I try this. It just isn't worth it. So your recommendation is probably still the best, even for my car.