Electric Superchargers...

[nhoj at cd.chalmers.se]

You wrote:
>
> From the "fluffy's stupid idea files"...
>
> We've all (or many of us) heard/read about the "electric superchargers"
> that have been marketed recently, these are devices which connect to the
> intake and blow in air - but they are electric powered.  They typically
> run for short bursts of time to provide just a little extra grunt when
> needed, and usually on naturally aspirated engines, especially diesels.
>
> Well, has anyone thought of doing this *right*?  Install additional
> alternator capacity to support running the unit consistently.  Put in an
> intercooler, etc. to support higher boost levels, like a real turbo.
> [snip]
> 4) No one else is doing it, so there must be some obvious problem that I
> haven't thought of.

There is kit for two-stroke motorcycles (dirt bikes, IIRC) that uses a crank  
mounted centrifugal compressor and one or more "secondary" electrical  
compressors. As I understand it, the electrical compressors are always  
runnging, and can be tuned to the optimum pressure. I think the centrifugal  
compressor doubles as an air filter, by the way...

I tried to get in contact with the company to discuss its application on  
marine outboard engines, but never got a reply. (I have a weak spot in the  
power band due to rather extreme port timings.)

I guess the main problem with an all out electrical system is that you're  
likely to need a high voltage DC generator, rather than beefing up the  
existing 12 Volt system. You'll also have mechanical losses from driving the  
generator. These losses, in addition to the electrical losses, will probably  
be a fair bit greater than the losses in a fully mechanical system.

Therefore, I think using an electrical compressor for a secondary stage  
makes much more sense.

Regards,
John Hornkvist