Dear Paul,

I have been reading many of the articles on your website, they are
very informative. I have been looking for a good engine for a heavy
duty gyroplane, and I was told a Subaru EJ25 is a good choice.
However, I have not been convinced. I would think the 13B would be a
much better choice. I owned a RX7 for many years, and when I sold it
after an accident it had well over 150,000 miles and the engine was
in perfect shape.

I have a couple of questions and hope you can help me out. First of
all, do they make brand new rotary engines? If not then we can only
buy old cars for the engines which is not easy to do in my country as
cars must be destroyed after 10 years. Second, how does the power
to weight ratio of the rotary compare with that of the EJ25? The data
I got just got me very confused. The power for the EJ25 ranges from
165hp to 300 hp. This sounds rather strange, and with such power
range the EJ25 could have rather high power to weight ratios too.

Best regards,

Gordon Gao

Mazda stopped production this year but they do that from time to
time as the market is currently saturated. They did that in 1995 but
started up again in 2004. There have been 2.5 million sold world
wide so there is no shortage of engines.

The rotary is in no way comparable to a piston engine. There are no
stresses in the rotary that lead to metal fatigue unlike a piston
engine. A 300 HP Subaru is a hand grenade. If you are not killed by
the shrapnel in the explosion the resultant crash will do it. :)

http://www.rotaryeng.net/What-is-a-rotary-engine4.html

http://www.youtube.com/watch?v=QOwb8QRHrMY


Paul Lamar


Does it fit a so powerful engine with such a lightweight flying
machines a Giroplane? I'ts just a question form a 100% novice, the
Austro engine with 40 KW sound good for that kind of Autogiro, that
probably with an engine so big would spend all the power just taking
up the engine weight.Can you give me some feedback?

Thanks, best regards, salut +

Jose Gros-AymerichE-28033 madrid, Spain

I don't understand the question.

Gyro's require high power as they are basically a powered parachute
:) They are in a continous state of auto rotation so to speak. It is
a brute force approach to flying.

Paul Lamar

Thank you Paul. For the 13B MSP, the 247 HP that people talk about
is sustained power?

GAO, Gordon

Yes.  One must re think what you know about internal combustion
engines. A rotary is more akin to an electric motor. There are thousands
of 100 year old electric motors still working every day.

In a rotary, just like in an electric motor there are NO REVERSING STRESSES!
It is reversing stresses that do the damage in the piston engine.

Paul Lamar