a functional hood scoop?
06-01-2003, 04:28 AM
#21
Contributing Member
Re the e-fan: Your 4Runner does have an e-fan, it pushes air through the AC coils when your AC is on. It's probably cheaper for the factory to put a clutch and a fan on the engine than it would be to have an e-fan, all the wiring and the temp sending units.
Re the electric compressor: lots of folks think that when they take off an engine-driven component and replace it with an electric component they will reduce the drag on the engine. Yes and no, but mainly no.
The energy to drive that component ultimately comes from the engine; it's just that the engine's mechanical energy now has to be converted into electrical energy by the alternator (some of which is lost as heat) travel through the wires (where some more of energy is lost as heat) and wind up in the electric compressor being converted back into mechanical energy (and again, some of it is lost as heat). In short, of the 100% of the energy at the crankshaft, by the time is goes through the conversions and the transport, you may get 30-60% of that energy actually cooling the vehicle's AC unit. So actually, by driving the AC units off the crankshaft, the automakers are not only making their AC units more efficient but are also saving some weight.
The same energy losses apply to the e-fan, however since it is a fan with a fairly small motor (your engine fan has a 150 hp motor driving it), it cannot draw as much air volume as a stock fan. The battery will supply some of the energy needed when it does come on. However, the battery is just a storage device, so once it begins releasing some of it's stored energy, the alternator has to begin converting the crankshaft energy into electrical energy to recharge it. And in the conversion process, some of the energy will be lost again to heat.
So we wind up with a problem, everytime we convert energy from one form to another, we lose some of it to heat. And everytime we change the position or direction of mechanical energy (by belts, gears, etc.) we lose some energy to heat. Hence the phrase, "there ain't no such thing as a free lunch."
The trick is to limit the losses.
Nothin' like a Sunday mornin' physics lesson, eh?
Re the electric compressor: lots of folks think that when they take off an engine-driven component and replace it with an electric component they will reduce the drag on the engine. Yes and no, but mainly no.
The energy to drive that component ultimately comes from the engine; it's just that the engine's mechanical energy now has to be converted into electrical energy by the alternator (some of which is lost as heat) travel through the wires (where some more of energy is lost as heat) and wind up in the electric compressor being converted back into mechanical energy (and again, some of it is lost as heat). In short, of the 100% of the energy at the crankshaft, by the time is goes through the conversions and the transport, you may get 30-60% of that energy actually cooling the vehicle's AC unit. So actually, by driving the AC units off the crankshaft, the automakers are not only making their AC units more efficient but are also saving some weight.
The same energy losses apply to the e-fan, however since it is a fan with a fairly small motor (your engine fan has a 150 hp motor driving it), it cannot draw as much air volume as a stock fan. The battery will supply some of the energy needed when it does come on. However, the battery is just a storage device, so once it begins releasing some of it's stored energy, the alternator has to begin converting the crankshaft energy into electrical energy to recharge it. And in the conversion process, some of the energy will be lost again to heat.
So we wind up with a problem, everytime we convert energy from one form to another, we lose some of it to heat. And everytime we change the position or direction of mechanical energy (by belts, gears, etc.) we lose some energy to heat. Hence the phrase, "there ain't no such thing as a free lunch."
The trick is to limit the losses.
Nothin' like a Sunday mornin' physics lesson, eh?
06-02-2003, 12:27 PM
#23
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Join Date: Nov 2002
Location: Staten Island, NYC
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CDub considers gwhayduke's for moment before going back to banging away at the hole he's making in the RebuiltWonder's tailgate to fit the shaft for a fan boat propeller driven by 1,932 half-used D cell batteries.
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