Quote:
Originally Posted by Old Mechanic
Pulse and glide will improve you mileage, especially if you glide with engine off.
It takes a certain amount of HP to just spin the engine with no load.
Combine that with transmission gearing that allows lower RPM at highway speeds and the P&G window for better mileage closes considerably.
You may find it effective up to a certain speed but after than the benefits will become insignificant.
Another factor is the aerodynamics of your vehicle. Very high CDs will cost you a lot of your energy in wind resistance, expecially in a large frontal area high CD truck.
Bottom line, I would guess the P&G will probably help up to about 45 MPH. After that the aero drag will probably kill any benefit especially at peak speeds of 60 MPH and above.
regards
Mech
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So, I have finally had the opportunity to drive on level suburban roads with a couple miles between stops.
Just going by an intuitive feel for the truck (no scangauge) I'm inclined to agree with you. The glides are more than twice the pulses, and it certainly isn't taking 2-3 times as much HP or fuel to accelerate as steady state.
Most of my driving has been dense city streets or freeway, and P&G was never practical, esp. considering anything below 25mph and I have to shift up, and anything above 40mph and my RPMs are excessively high due to no overdrive.
Seems P&G between 25 and 35 though is the sweet spot for this truck.
Of course, unless I find a route that I can maintain that for a hundred miles or so, I guess I'll never know just how much it helps.