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Along the lines of what Ken Fry posted. The University of Maryland had a dyno setup. They were testing a GM Iron Duke 4 cylinder push rod engine, old tech.
At 1200 RPM (may have been slightly higher) they loaded the engine to 20 HP. I don't remember the exact quantity of fuel consumed but lets just call it 1 unit.
Increasing the load up to 50 HP the fuel consumption increased by 50%.
Basically you had 20 HP per unit of fuel, versus 50 HP for 1.5 units of fuel, which closely follows Ken's figures. The extra 30 HP only took half again as much fuel as the first 20.
That's the secret of P&G.
AS long as you know the RPM range for best BSFC and the manifold vacuum reading at 90% load (about 2.8 inches) you know you are in best BSFC as long as you keep the RPM in the range on the graph and the manifold vacuum precisely at 90% of atmospheric pressure.
In Neil's post on this thread he stated that electric motors are 2-3 times as efficient as IC engines. He did not specify which motor or engine, but made a general statement.
In fact if you take specific engines and loads his statement is far from factual. Best BSFC on the Wiki site for is 54.4% (admittedly not a practical passenger car engine, but such limitations were not demanded). No electric motor is over 100% efficient much less over 150% efficient so without limitations his statement has issues.
With the best passenger car engine as an imposed limitation best BSFC is right at 43% and there certainly are electric motors that are better than 86% so using that logic he can claim credibility. The problem with that is when you understand there is a 15% loss in charging a Nissan Leaf, the only commercially available all electric car today, even if your vehicle was perfect it could still never be better than 85%. When you buy liquid fuel, you don't have to pay 15% of the volume in loss to get it in your tank. You must also limit your electric motor choice to the same passenger car limitation, not even considering the weight of the energy storage system.
Electric motors also have BSFC maps, with a peak efficiency figure. Claiming that as the efficiency of the motor is just as wrong as claiming the peak BSFC for an IC engine is the best it can produce. Agendas that ignore facts are fallacious. The cost of electricity is what it cost at your meter. The cost of fuel is what it costs at the pump. If that cost is lower because it is subsidised by taxpayers then it should not be subsidised, because it puts my money in their pocket, which to me is simply wrong.
Pale Melanasian can almost equal the fuel consumption of a Nissan Leaf in his 96 Civic, using his considerable skills and route choice and low average speed. If he drove a Leaf and used the same techniques, the Leaf's fuel consumption would considerably exceed EPA figures, so that is a fair apples to apples comparison, but the Leaf would not be twice as efficient, so his rationale about electric motors is not quite correct. Also consider the generally accepted practice of not charging the battery to 100% or discharging it to below 20% and the fuel tank on the Leaf just shrunk by 40%.
Without engine design optimization, the power train is the secret to higher efficiency. 80% mileage improvement is a practical figure for a power train that allows only best BSFC engine operation. It's also possible with current technology to make an engine better than 40% efficient on gas and closer to 50% on diesel if you optimize the engine for only operating at best BSFC instead of using throttling to control power output, or in the case of the diesel super lean burn AF ratios.
regards
Mech
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