Audi are perfecting the electric supercharger!

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At first I thought it was a truly electric supercharger, with virtually no parasitic mechanical loss, which it looks like it is. That could give the immediate throttle response a supercharger tends to have.

From the diagram, it looks like it still has the exhaust-driven turbocharger.

I wonder if the supercharger is meant to handle slow speed/light throttle while giving the turbo charger (which could be a lot larger now) time to spool up.

Even if you didn't combine it with a turbo, a free-standing supercharger on a small engine could make it feel a lot more muscular at low/moderate speeds, with less risk of cooking the oil from the heat a turbo produces.

If placed on a hybrid for example, it could give some serious low / moderate speed punch while diving through holes in traffic or for passing. Then have the electric motor for miserly mileage in stop/go city cycle driving.

Just musing into a happy New Year....
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An interesting problem. I don't know what the typical power in a turbocharger itself is (i.e. the power required to compress the incoming airflow) but I suspect it quite a few horsepower. It helps to look at the engine as an "air pump". For example, a 2L engine spinning at 4000 RPM should be moving on the order of 150 CFM (if my rough calculations are correct). To take a 150 CFM airflow and compress it to say 10 PSI requires quite a bit of power.

That's why those "electric turbochargers" for sale on ebay mentioned above (I know, you were being funny
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, I didn't even know they were selling them) are a waste of money. At best they're just "windmilling" in the airflow, at worst they add a pressure drop to the intake system IMO.
 
No problem with parasitic loss; just attach a two stroke motor driving an electric generator to generate the electricity; the two stroke, of course, will require a special spec oil.
 
The electric supercharger has been the "holy grail" of power adders for 100 years. Not until recently has the technology been available and fully capable, of driving a compressor with enough power, in a compact enough package, and to have enough battery power to do the job.

A 3 phase, compact AC motor, a controller and a very "energy dense" battery will be part of such a package.

What many people don't understand is the actual HP required to drive such a compressor. In race cars, it's commonly said that the turbocharger shaft is often carrying close to the same HP as the engine's crankshaft! (not really true, it's substantially less) But, it does illustrate a point. There is serious power being transfered from the turbine to the compressor! It's not just 4 or 5HP.
 
But you still have to carry around a battery to power it all the time.

Some years ago, somebody managed to make some acceptable dyno gains by powering the compressor side of a turbocharger with some high speed electric motors to "supercharge" his engine. The downside? The weight of the 3 Optima batteries in his trunk to power the fool thing.

I wondered why he just didn't use the electric motors to drive his undriven wheels. De-facto on demand AWD.
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My response is ugh, that's going to be an abortion of a design to fix stuffed into the nose of an Audi.

Why make something so simple, so complicated? I rather have slightly slower throttle response and more simplicity.

Something like an 06 or 07 E320 CDI will crack 40mpg on the highway, is peppy enough, and is SIMPLE! Diesels are so ruined.
 
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The only engine I've seen numbers for is the 1951 Alfa Romeo Alfetta. It had a dual stage supercharged 1.5L straight eight. It would put down 425 hp to the wheels. The superchargers used another 175 horses. If you compare the hp used by the supercharger to the net hp, that 50% figure is not too far off. I have no trouble believing that a more modern engine may equal that 50% by that method of comparison.

Ed

P.S. The blocks for those engines were first used in 1938, 1951 being the final use of them after the war.
 
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I think it's a cool thing, and could definitely be done. I don't see why it could not simply use a, or multiple, capacitors and run off the power of the car's alternator (making more power than a regular alternator, obviously). They share the same belt in regular SC compressors, and I imagine that it would take maybe 3-5bhp to power the SC, rather than the current 10x than that, or more, it takes now.
It would really be ideal for a twincharged setup, utilizing a large turbo and small supercharger configuration. The electrical power required to spin even a twin screw type (would be ideal for this application) pushing just 4-6psi or so would not be un-doable at all, and feeding that into something along the lines of a moderately large Garrett turbo would result in linear boost progression all the way to a sky high redline, a constant minimum boost pressure which would negate pretty much every downside to turbo motors, and the engine would be extremely efficient AND produce seriously large amounts of power due to the benefit of a near zero "power cost" to drive the FI setup. I would probably run a pair of intercoolers, a small one between blowers and a large front mount post turbo, and I could see an easy 200bhp+ per liter of displacement.
Imagine a 2L I4 setup as such, making 400-450bhp from the factory, and getting 38-44mpg!

Would be very tuner friendly, as the constant boost pressure would allow a significant amount of room for tweaking the turbo and consequently shifting the power curve in either direction, faster spooling and more responsivewith less peak, or more top end with a llittle longer wait for the turbo to be making full boost.
 
Originally Posted By: nleksan
I think it's a cool thing, and could definitely be done. I don't see why it could not simply use a, or multiple, capacitors and run off the power of the car's alternator (making more power than a regular alternator, obviously). They share the same belt in regular SC compressors, and I imagine that it would take maybe 3-5bhp to power the SC, rather than the current 10x than that, or more, it takes now.


Thermodynamics.

It would take more power to turn the alternator to generate the electricity to power the electric motor than it would take to just turn the supercharger.

Assistance by the capacitors would help, but you still have the additional weight of the capacitors which will negate some of the gains. There is still an overall increase in parasitic draw and more weight to carry.

You can't get something for nothing, you can't win, and you have to lose.

I like the idea of using a small electric motor to help spool up a turbocharger, but not driving the supercharger. The exhaust is still driving the turbine, just has a little assistance to get spooled up.

I really wonder why they haven't used a motorscooter CVT to drive a centrifugal supercharger. You could vary the pulley diameter mechanically or have a program that allowed full variator adjustment at appropriate times.
 
During the early 90's a company introduced an electric turbocharger (actually a supercharger) for a few two-stroke Detroit Diesels....the name was Turbodyne....still shown on the internet.

We tried a couple of them to get away from the terrible acceleration lag on 6L71 DDEC's. The electric super provided boost pressure so the DDEC control would add fuel.
 
Consider my point above. Superchargers need massive amounts of power. A 12V car battery "might" have 40 Amp Hours max capacity, and only 1/2 of that is practical.

The math:

Note 746 watts=1HP. but 1000 watts is required to make 1 real HP.

Car battery has 12x20=240 watt/hours

So, a car battery can make 1HP for a few minutes. Not nearly enough for a supercharger! But can a car battery make the required 100HP for 15 seconds??? The answer is absolutely not. That would require 100,000 watts for 15 seconds, or 8333 AMPS at 12V.
 
^^^That's the principal reason the mfgrs want to raise the voltage in cars electrical systems.

It could also reduce the weight significantly...
 
IIRC, the electric super required an extra alternator to power it and that was the weak link. I'd have to dig up the original papers on it but (again if I remember correctly), it only ran for a couple of seconds each time. It was basically used to "fool" the electronics (provided an alternate pressure boost) to enable the turbo boost sensor to begin adding fuel.

The original configuration used the turbo boost sensor to minimize fueling until adequate boost was present to prevent excessive exhaust smoke upon acceleration. While the system did indeed limit smoke, it also slowed take-off so much that buses could not make it through a traffic signal before the signal turned red again. The electric super provided boost pressure that signaled the ECM to add fuel and the additional air and fuel allowed the bus to accelerate normally.

It did work very well when it worked but it was very short-lived due to reliability problems.
 
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