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Old 04-29-2012, 07:10 PM   #7 (permalink)
brucepick
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Outasight - '00 Honda Insight
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Quote:
Originally Posted by JRMichler View Post
And one more variable for the calculations: Everytime you kill the engine, you throw away the rotating kinetic energy in the engine. You could be better off getting real proficient at DWL and DWB.

Good data beats 1000 hypotheses.
There's probably some value to the kinetic energy of the rotating engine. HOWEVER remember you need to provide fuel to keep that thing turning. That's where you get a big benefit from moving with the engine off, as long as it's safe to do so.

Reciprocating pistons and loading/unloading the valve springs etc. all require some energy, not to mention the alternator, water pump, power steering, and the fuel pump that all will likely keep running unless you've put them on vacation.

My Civic, before doing the EPES (aka alternator-delete), needed right around .18 gallons per hour to idle at 670 rpm, fully warmed up. x 3 = .54 gph for 2010 rpm which would be maybe 55 mph in 5th gear?? If you're getting 55 mpg at 55 mph, that's 1 gallon per hour. And .54 gallon of it is to keep the engine turning!

My point is that you are using significant quantities of fuel just to turn the engine. That's why some of us are very keen on killing the engine for coasting.

My MPGuino reported that at last weekend's Green Grand Prix, I drove just about HALF the distance with the engine off. Usually these days I get low 50's mpg with the engine off may 10-15% of the distance. But at the GGP I scored 62 mpg.
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