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-soD(is it ok if I use the acronym to reference you?. . .its alot shorter lol)
You're right I know for a fact you would be adding weight. I assumed you would be essentially adding a secondary engine(in the case when the ICE is not downsized). So it would be a substantial amount of weight.
The SES suncatcher employs a system that is smaller than a 400cc engine. Weight wise who knows? I don't. The parts could conceivably be made from aluminum and then it would be light(lighter than a block of steel. . .) Bonus point no cooling system required(although 10lbs is way under what the stirling would weigh). The engine could be. . .Aspirated?. . .naturally because the engine's system is based off heat difference and heat syncs on open air and even more effectively when exposed to wind created by driving.
To the point, the 400 CC produces 25 KW(33 HP).
Drop Trans 10 lbs additional 10-15% efficiency gain(mechanics of trans are not FE)
Drop Axles 20 lbs additional boost, no wasted uniform acceleration
Drop differentials(front or rear or both depending on car) 10 lbs additional friction gains
Drop CV joints(FWD+AWD only) 2 lbs additional friction gains
These are underestimates. I'm pretty sure the components weigh more so I tried to low ball since I don't have actual numbers(the trans power loss depends on your model but its legitimate).
Add
2(4) engines 50(total or 75ish for four) pounds 5% energy loss in conversion(electric to mechanic)
2 stirling engines 70 pounds 1/4 recovery of lost energy(efficiency of 25%(actual are up to 68% and av is 50%))
1 larger alternator 20 pounds more than old alternator 5% loss in conversion(mechanical-electric)
2 standard batteries 80 lbs
let's assume my Del Sol is the test car.
dropped 42 lbs and gained 200
+158 lbs
added (1/4 of energy input to stirlings(100 hp)) 25 HP
The formula is 1-2% for every 100 lbs(?) so 4%(high-side)
101 hp +25 hp =125 HP
25/101 ~ 25%
25%-4%=21% increase
Gain of 6.5 mpg
This ignores that the alternator, electric motor and electrical wiring is more efficient than. . .Trans, Drive shaft, Axle, Differentials, and finally joints.
a negligible amount of power is lost in the cables and the overall % lost through the conversions would be 10%(equal to the trans of a manual alone).
this also does not account for energy stored in the batteries when coasting(engine on) or traffic stops(engine on). The batteries could come in to play here and get the car through the energy expensive acceleration phase and recharge off the idle and regenerative braking.
Ignoring energy saved in the bats or friction savings if you bump to 50%(17-19% behind SES) my del sol jumps to 52.5 MPG(50% increase). Even the Prius, Camry and other hybrids don't come close lagging 6 mpg behind.
Somehow the Aptera still beats it(I suppose they are doing something similar but with a much lighter vehicle(1500 lbs opposed to 500) better aero frame(drag of only .011 .11 whichever is amazing but not unreasonable(can't remember where the decimal goes ^_^)) and probably is using smaller motors than an equivalent 100 horses.
If you really really wanted to get picky about it. . .drop the aluminum,steel whatever shell you have replace everything with carbon fiber(frame of titanium or aluminum) put 13-14 inch tires on, replace the glass, take out everything that is not drive essential, drop engines to 100hp aluminum engine, add a stirling on the engine block to salvage that other 20-30% sneaking off the block and you could find yourself in Aptera land without the extra batteries or three wheels.
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