Hi Paul,

I enjoyed your site very much.

I am fascinated very much by the wankel concept. I am looking to buy a
cheap 1st
airplane running almost out of engine hours with the plan to replace the
engine by a
Mistral.  But I talked a lot to RX7-8 owners all saying that you need a
new engine every
100.000 km because of wear and tear. Why do you claim then this robustness
and longevity
in a wankel?

thx!

Rudy Berkvens
Wuustwezel
Belgium
Europe.

I can't explain it. Perhaps they are talking about the NSU RO80. Here in
the states the
Mazda's last 300,000 to 400,000 miles (not Km) if the cooling system and
oil supply is
taken care of. Thousands of 20 year old RX7s are still on the road. They
dominated 24
hour endurance racing in the 1980's and won the 24 hour Le Mans outright
in 1991. They
are still winning here in the United States in the Rolex GT class despite
severe
penalties on max RPM and minimum car weight.  Many Mazda Wankels installed
in aircraft
running at 75% full power are lasting hundreds of hours and in some cases
over 2000
hours. To my knowledge nobody has worn one out in an aircraft yet.

Yes they burn 5% more gas but that is more than made up for by the ability
to burn car
gas instead of more costly aviation fuel. When somebody builds a turbo
compound version
they will become the most efficient internal combustion engine of all
time.

Paul Lamar


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Good news!

I agree with the turbo compound statement.

No engine is so fit to be blown full of air at high pressure - even several
bars. The only point of attention is to get rid of all the heat. Working at
a higher temperature and pressure will increase efficiency largely and if a
second turbo is connected to an electric generator charging a supercapacitor
(no not a flux capacitor :-)) of say 5 megajoule which in its turn drives an
electric engine connected directly to the engine shaft, you will win
possibly 10% of efficiency. Ideal would be if the electric engine is mounted
before the combustion engine and that a freewheel exists between combustion
engine and prop so that the prop can be driven by the electric engine alone.
that electric engine, when the combustion engine fails, will be able to
continue delivering a limited power for a few minutes sufficient for an
altitude gain of +-1000ft allowing for a neat landing or drawing the BRS
safely -  on the supercapacitor's energy.  Thus combining an engine failure
backup system as well as an energy saving turbo compound system.
On top of that - but that is maybe more for cars who don't mind the extra
weight - part of the cooling heat could be fed into a small stirling engine
delivering power to the supercap too, thus regaining a few extra procent of
efficiency. That would total up to an  efficiency pretty comparable with
that of a reciproke diesel.

Why keep my ideas for my own? I don't have the money and means anyway to
realise them. Better share them with people who can.

Rudy Berkvens