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LSxcellent · 12-15-2007, 10:30 AM

As a data point... it takes 125hp to run the supercharger on a Mustange GT500 at full boost.

Just to put that in perspective, that is ~93,000 watts. If you assume you are running your motors at the cars nominal 12v, that means your motor will be consuming about 7750A. The BIGGEST batteries I can find have about 55Amp/hours of capacity, and since your battery would be supplying most of the power required to run the supercharger (your alternator would die or stall the engine if it had to supply this) you can expect about 25 seconds of runtime at these power levels.

You can use this math to extrapolate how much runtime/power you'll get, but all in all its not much.

Also keep in mind the energy-transfer-efficiency rule... everytime you change the 'flavor' of your power, you lose some to efficiency. So in your case, you are taking the mechanical energy of the engine, turning it into electrical energy with an alternator (loss), storing it in a battery (loss), turning it back into mechanical energy with a motor (loss) and then compressing air with it (big loss).

A regular supercharger just starts with mechanical energy of the engine and compresses air with that... much less overall loss and better efficiency.

Turbo's actual take advantage of the hot-expanding-exhaust-gas (which is otherwise wasted energy) and they capture this 'waste energy' and use it to compress the air (overall better efficiency again).

If I were you... I would do this:

-Start with a turbocharged system (best overall efficiency)
-Use your electric supercharger idea to make a 'zero lag' system. Something that spins the turbo up to speed in no time.
--You can use an extra fan on the exhaust blades to spin it up (idea 1)
--You can mount the electric motor to the turbo-axle and spin it directly with the electric motor (probably requires some gearing and a one-way clutch) (idea 2).

This way you have the boost-response of a supercharged system with the overall efficiency and power potential of a turbo-charged system.

FYI, I make military robots, so I've done a LOT of work with motors/gears/efficiency calcs etc. Feel free to ask more questions!

~LSx

12-15-2007, 10:30 AM	#10
LSxcellent Drives: MINI Cooper S Join Date: Jan 2007 Location: Boston, MA Posts: 284	Efficiency Efficiency Efficiency! As a data point... it takes 125hp to run the supercharger on a Mustange GT500 at full boost. Just to put that in perspective, that is ~93,000 watts. If you assume you are running your motors at the cars nominal 12v, that means your motor will be consuming about 7750A. The BIGGEST batteries I can find have about 55Amp/hours of capacity, and since your battery would be supplying most of the power required to run the supercharger (your alternator would die or stall the engine if it had to supply this) you can expect about 25 seconds of runtime at these power levels. You can use this math to extrapolate how much runtime/power you'll get, but all in all its not much. Also keep in mind the energy-transfer-efficiency rule... everytime you change the 'flavor' of your power, you lose some to efficiency. So in your case, you are taking the mechanical energy of the engine, turning it into electrical energy with an alternator (loss), storing it in a battery (loss), turning it back into mechanical energy with a motor (loss) and then compressing air with it (big loss). A regular supercharger just starts with mechanical energy of the engine and compresses air with that... much less overall loss and better efficiency. Turbo's actual take advantage of the hot-expanding-exhaust-gas (which is otherwise wasted energy) and they capture this 'waste energy' and use it to compress the air (overall better efficiency again). If I were you... I would do this: -Start with a turbocharged system (best overall efficiency) -Use your electric supercharger idea to make a 'zero lag' system. Something that spins the turbo up to speed in no time. --You can use an extra fan on the exhaust blades to spin it up (idea 1) --You can mount the electric motor to the turbo-axle and spin it directly with the electric motor (probably requires some gearing and a one-way clutch) (idea 2). This way you have the boost-response of a supercharged system with the overall efficiency and power potential of a turbo-charged system. FYI, I make military robots, so I've done a LOT of work with motors/gears/efficiency calcs etc. Feel free to ask more questions! ~LSx __________________ "When you turn your car on, does it return the favor?"