Turbochargers produce alot of power at high rpms.

Supercharger do not have any "turbo lag".

This is a question for the turbo experts here.

Would a turbocharger powered by an electric motor be practical?
It would always be running at a highspeed from the moment the car was turned on. The pressure produced would always be constant and there would be no "turbo lag"

What are the downsides to this design? Is weight a problem?

This idea came to me after seeing the S2000's electrical steering pump.

 

try to find an electrical source to power the thing that pushes that many CFMs to actually make a difference

 

Why not just get a supercharger? That much electric drain would soak up just as much power as a supercharger unit.

 

Moving to FI

 

They actually make a belt driven type turbo called Autoroter(SORRY I MEANT TO SAY "Rotrex" NOT Autoroter!!) but they really don't support that much horsepower and they still have a boost delay. A well designed turbo system will have very little lag but it's actually helpful because it helps the car hook up vs. a roots/screw style supercharger that hits the tires with instant boost.

Someone does make an electric roots style supercharger that uses a trunk full of batteries but it's very limited on how long it can run between charges. It's next to impossible to beat the efficiency of an exhaust driven turbo. Trying to achieve 90-100,000 RPM shaft speed with any electric motor would be next to impossible in a system that will work in a small car.

 

The Autorotor is a belt driven supercharger operating on the twin-screw Lysholm principle (unless Autorotor is now making some other types that I haven't heard about). Being a twin screw it has the same kind of PD boost curve as a roots. A PD blower only "hits the tires with instant boost" when the driver thinks the throttle is an on/off switch. PD blowers give boost on demand, while you have to wait for a turbo (though with a good design it's well worth the wait ).

A belt driven turbine type supercharger is called a "centrifugal supercharger." Take a look at a Comptech or Vortech supercharger; You'll see a single snail that looks for all the world like 1/2 of a massive turbocharger. It is, in fact, a belt driven turbo-supercharger (as opposed to an exhaust driven turbo-supercharger, or just turbo for short, which has two snails and no belt).

The big rub with electrical drive is the power and current that will be required. I don't have any real world numbers, but it takes more than a few horsepower to drive a blower. Look at a 2 HP electric motor, then imagine a 10 or 20 HP (or more) electric motor. We're talking BIG motors with massive current demands, especially when starting up from a standstill. I've seen the ads for the electrical superchargers that are supposed to add 1 HP, but I remain skeptical.

 

Check out Boosthead.com for electric motor driven compressor. Good idea, but right now battery technology limits unit to brief <15 second bursts of boost operation, then driving off boost for 'a while' to recharge battery. As battery and electronic capacitor technology improve, this %duty cycle will increase, and I expect this product to catch on. The base kit runs electric motor, therefore compressor, at fixed speed. So boost pressure drops as RPMs climb. I have thought of controlling the speed of the compressor by controlling the voltage going to electric motor. DC electric motors are very easy to control - more volts, more speed, more boost pressure and mass air flow. Seems like the voltage regulator circuit from an automotive alternator should be able to handle the high amperage drawn by the electric motor. This voltage regulator would replace the boost solenoid that throttles the wastegate on a turbo.

 

Thanks for catching that, I meant Rotrex not Autorotor. Rotrex are belt driven turbo chargers. They use off the shelf compressor housings.

I'll make the appropriate correct in my previous post so people don't get confused.

 

I hadn't seen the Rotrex stuff before, but their Web site says that they are centrifugal blowers. They don't *look* like conventional centrifugal blowers, and I could not find any drawings or descriptions of their internals. How do they differ from other centrifugal blowers (other than the patented "traction drive")?

 

No such thing as a belt-driven "turbocharger". All forced induction methods I know of (Roots, Lysholm, centrifugal, turbochargers, etc) are superchargers. A turbocharger is just a supercharger that is driven by a turbine. A belt driven turbocharger is redundant.