Vance W Jaqua wrote:

The new Motor trend mag has a driver report  RX8- complained about
low torque - Vance

I am not surprised. I suspect he was not used to a rotary and a six
speed gear box and did not understand that one could not just floor it in
any gear above first and have it pull strongly away in the piston
engine RPM ranges.

I was thinking about that today. Instead of a six speed auto transmission
Mazda ought to think about installing a supercharger.

Paul Lamar

Robin Ream wrote:

Hi Paul,

    This is the first time in a long time we've heard you mention
"supercharger" in the same sentence with rotary applications.  -  We thought
you were a turbo only guy.  Now that you've opened Pandora's box, what are
your thoughts on supercharging a rotary (pros & cons)?

Thanks,
Robin

A car is different than an airplane. Car people expect to nail
the gas and have the car accelerate well regardless of the gear it
happens to be in. A mechanical drive supercharger achieves that better than
a turbo charger. A turbo charger has inertia and the turbine must
spin up to generate boost. This cause an acceleration lag in a car
but is of no consequence in an airplane.

Turbo chargers make some use of the 50% wasted energy in the 
exhaust to drive the compressor. Super chargers on the other hand 
must sap all of their required mechanical energy out of the engine 
it self. In other words if the supercharged engine generates 300 net 
HP something like 330 HP will be required to be generated by the 
engine. It is true that the turbo charger puts a bit of
back pressure on the engine. The ratio of net HP out to gross HP 
generated is much better I expect for a turbo charged engine.
This translates to less stress on the cooling system, the engine
itself and better fuel mileage. I don't have the exact numbers 
but Jon Lauter may have these numbers as he is assembling and 
selling supercharged rotaries for use in boats.

Many WW II aircraft engines used both.  The radial piston engine
had bad mixture distribution due to its vertical spider intake 
manifold configuration.  A centrifugal super charger with a 
carburetor on the intake side  was almost necessary to solve 
that problem. Other wise the lower cylinders would run much richer
than the upper cylinders due to fuel droplet separation
in the intake manifold. 

Recent developments in car supercharges has improved the efficiency
over the roots type and has incorporated an electrical clutch
between the engine and super charger so the super charger can be 
disconnected when the car is cruising down the freeway using
30 HP and the super charger is not needed. Saves gas. Not a 
viable option in an airplane as we need 150 HP or more
and boost at high altitude.

Paul Lamar
 
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