Quote:
Originally Posted by COcyclist
The pulse and glide works for a gas or petrol vehicle because that engine is less efficient at part throttle and light load. Our diesels don't have a throttle plate so the is much less restriction to the air pumping through the diesel engine.
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I thought that was all pulse and glide was about too at first. I have since been schooled better (by the good folks here on ecomodder)
Pumping losses are part of the equation, but not all of it.
Another part is just that all ICE engines are terribly inefficient, at any speed.
The maximum efficiency of a diesel is something like 40%, and that's before accessory and drivetrain losses.
If your glides are 3 times as long as your pulses (they are for me), but it takes less than 3 times as much fuel to accelerate as to hold steady, then you come out ahead just due to the fact that the engine is off for more time than it is on. It works because the engine uses more fuel just to turn itself than it does to actually move the vehicle.
Of course, if it took more than 3 times as much fuel to accelerate as to hold steady, then you'd be better off not using P&G.