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
Paul.... I can be a friend here...
Gordon, I have built and flown many gyroplane hours on both. I currently
own the Mad Max Tandem LTC with a Sub 2.5L. (it's even for sale if you want
to go straight to flying!) Previously, I've built two other gyroplanes each
of those with 12a's that were ported as well as another that was a subaru
2.2l. NO QUESTION that the rotaries were more powerful (209, and 219 hp at
7500 rpm) and their weights were significantly less than the 2.5L Sub (about
40# lighter!). MY current ship's Sub has been intake polished, Cam shaft
ground, exhaust valves replaced, and EFI computer reflashed with a
different MAP. The Subaru stuff can be overseen by Don Parham in Oklahoma
(IF he hasn't been blown away by the storms!) Based on a rate of 13 gallons
per hour if I have the throttle wide open (5000 rpm), I'm only making about
175 hp. When I had the 12a's, one would eat at a rate over 14-15 gallons
per hour, the second would push all the way to almost 17 gallons per hour.
Any Subaru making more than 200 hp has been signficantly altered and/ or
turbo-supercharged... and as such will be finicky and should ALWAYS be
suspected as a failure in the making.
My 2.2L made it to 800 ish hours before it was sold.. still running fine.
BOTH rotaries were sold past 400 hours each and running fine... the current
subaru 2.5L is at 385 hours and seems to be clicking along... Paul will
tell you it's an exhaust valve time bomb... I tend to agree, but the hours
for the subaru seem to be flying longer than any GM or Ford engine (even if
significantly altered!). Engine outs are always the MOST dreaded sound in
aviation... but when they happen in gyroplanes, we aren't NEAR as worried as
fixed wing applications. So... yes, the subaru 2.5 is heavier... mine is
HEAVILY modified and seems to be making about 175 hp. However, it is using
the EFI that was in the automotive application (with a modified/ flashed
chip) so tuning is a cinch! The rotary is simplistic, burns a touch more
gas, but has power on demand. I would ONLY recommend using a planetary
PSRU... please don't even think of a spur or belted redrive. That's just
too much horsepower for those other systems!
IF you are ready to fly NOW, I have my tandem ship with Sub 2.5L that is for
sale! Contact me off of the newsletter at
garybuster@gmail.com!!
Gary Buster
T25 East Texas
I would tear that soob down and check the rods and crank for cracks.
A gyro is safer as you usually land almost anywhere.
Paul Lamar
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