As reported on the fastcar site, a centrifugal supercharger attached to a two speed automatic gearbox, promising 85% efficiency

Expensive, but one can expect the price to come down. Something to ponder

 

I already posted this in the general automotive section. It too had no responses.

 

Apologies I'll kill it if you like

 

The McCullugh that was to original Paxton used a two speed pulley setup operated by solonoid. That was the first two speed centrifugal supercharger.

And when you get 85% efficient centrifugal compressors you better call someone.

 

I always wondered why nobody developed a geared supercharger. The high rpm limit of the Renesis would seem to warrant the ability to have different gearing, so that you could keep the super in it's island.

 

ok .. i dont get the whole supercharger / turbo bs .. if you need high pressure air why not pick up a compressor with a can from home depot put a 7-10lbs limiter on the output and plug into the engine? so why? can someone set me straight here

 

****! Why didn't I think of that???

But, it would have to be a reeeeeeeaaaalllllllllly big can.

 

Yep...I have a Monty Python-esque picture in my mind's eye of the RX-8 totally dwarfed by a H U G E aerosol can on the roof

 

yea, you could tow it behind the car in a trailer

 

The can would be on the roof, the compressor would be in the trunk and the extension cord would be really really long.

-Mr. Wigggles

Ps. If it helps, think of an automobile engine as a 200 HP gasoline powered air pump that happens to have 3000 lb load attached.

 

Now to something completely different ...

So this supercharger with transmission has two speeds. Is that enough for a centrifugal? Don't centrifugals have about 1500 RPM sweet zone of operation? Wouldn't you need three or four gears for a car like the RX-8 or any high reving auto?

Also since when has any automatic transmission on anything led to an end product that was "85% effiecient"? Surely when the supercharger is switching gears its not going to be 85% efficient.

Also I would think you could have some really wild fuel management issues with Supercharger that switches gears at certain intervals combined with a driver who switches gears and modulates the throttle whenever he damn well pleases. Some whacky combination of the driver and supercharger behaviour could generate a sequence of events the fuel manangement doesn't know how to handle or wasn't tuned for. Replacing engines is very expensive trial and error tuning.

I think this two gear supercharger really is an OEM item and not well suited for the aftermarket world because the implementation will likely require some good coordination with rest of the car's electronics. Only the OEM is going to have that full control. Tuners trying to slap on something like this might be in for a risky venture.

-Mr. Wigggles

 

A single speed supercharger or turbo that's 75% efficient, is only that efficient at a small portion of it's operating range. The idea here is to get to that range early, and then as you pass it, to shift to high gear and get to that range again. This way you can get a better power curve across the rev range, and the centrifugal blower can be less peaky and the car can be more liveable on the street.

That's how I see it, anyway.

Take a look at a dyno for a Vortech or Comptec supercharged S2000. They make a little more power than stock up to around 6000rpm, then power rockets up from there. 2 speeds would allow for a peak in the lower rpms along with the one in the upper rpms.

Me, i'd just use a twin screw charger.

 

^^ Isn't it because of the VTEC that's causing the sudden boost in power?

 

I'm sure Vtec has a little to do with it. But Vtec is not some magical "turn your car into a supercar" device, it's just vvt. Slap a centrifugal unit on any engine and you'll see the same type of curve. I just used the S2k because of it's similar rev range.

 

I think the idea would be that the supercharger would switch gears consistently at a certain RPM (and maybe load). To make it a driver or "on the fly" controlled function would be pretty risky, for sure. To have it switch gears in the same situation every time would be controllable, I would imagine.

 

Holds interesting prospects for the future, but I'd rather see more stuff with axial flow superchargers in automotive applications.