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dcb · 07-22-2010, 10:07 PM

regarding option 3 (turn the engine over with an electric motor and drive the car that way). Most cars already have a motor that turns the engine over, the starter, so it is easy to get an approximate idea how much power/efficiency that will cost.

If your starter takes 200 amps, at 12ish volts, thats a 3.2 hp penalty for turning over the engine at sub-idle speeds, say 500 rpm. If you need 3000 rpm then you need at least 6 times 3.2hp to keep it running, or 20 hp, probably a lot more.

This is totally wasted power from the battery to wheels perspective for option 3.

Compound with extra weight/cost of the electrical setup.

The other aspect is if you "boost" the stock engine during cruise you will move the engine farther from bsfc and reduce its efficiency.

Just my $0.02, maybe I'm wrong.

07-22-2010, 10:07 PM	#23 (permalink)
dcb needs more cowbell Join Date: Feb 2008 Location: ÿ Posts: 5,038 pimp mobile - '81 suzuki gs 250 t 90 day: 96.29 mpg (US) schnitzel - '01 Volkswagen Golf TDI 90 day: 53.56 mpg (US) Thanks: 158 Thanked 269 Times in 212 Posts	regarding option 3 (turn the engine over with an electric motor and drive the car that way). Most cars already have a motor that turns the engine over, the starter, so it is easy to get an approximate idea how much power/efficiency that will cost. If your starter takes 200 amps, at 12ish volts, thats a 3.2 hp penalty for turning over the engine at sub-idle speeds, say 500 rpm. If you need 3000 rpm then you need at least 6 times 3.2hp to keep it running, or 20 hp, probably a lot more. This is totally wasted power from the battery to wheels perspective for option 3. Compound with extra weight/cost of the electrical setup. The other aspect is if you "boost" the stock engine during cruise you will move the engine farther from bsfc and reduce its efficiency. Just my $0.02, maybe I'm wrong. __________________ WINDMILLS DO NOT WORK THAT WAY!!! Last edited by dcb; 07-22-2010 at 10:20 PM..