Jabiru had their 8-cylinder engine on display at Oshkosh in July/August and
they were taking orders at an introductory price of US$15,600. If I
remember correctly, delivery would start in January. The numbers on the
engine are very impressive, so it will be interesting to see what the user
experience is. Like you, I am not impressed with the 4-cylinder Lycomings.
I usually fly a Cessna 172P with a Lycoming O-320. Compared to my brother's
Cessna 172B with a 6-cylinder Continental O-300, the 172P is a flying
"Relaxerciser".
My feeling in regard to most auto conversions is that they need to be
derated some from their claimed power rating. One check that I use is to
calculate the brake mean effective pressure (BMEP) in psi. BMEP=150.8*T/V,
where T is the maximum torque rating in ft-lb and V is the volume
displacement in cubic inches. This formula applies to 4-stroke engines.
Most naturally-aspirated engines fall in the BMEP range of 140-150 psi, so
anything larger should be viewed with suspicion. Supercharged/turbocharged
engines will have a higher BMEP so the formula is not a good check on those
engines.
You can also work the formula in reverse to calculate a torque from a BEMP.
If I want to calculate the torque at maximum power, you should use the low
end of the BMEP range. So at maximum power a 2.5-liter (150 cu. in.) engine
would produce about 140 ft-lb of torque or maybe a little less. Another
formula gives the rpm of that condition: N=5252*P/T, where N is the rpm and
P is the horsepower. The 2.5-liter engine would be screaming at 6750 rpm to
produce 180 hp. Do you want to fly behind an engine that has to turn 6750
rpm to make its rated power? Perhaps I have ranted too much, but this is a
long-winded way of saying that the claimed power should be derated in
aircraft applications. By the way, the 2.5-liter engine in my car is rated
by the manufacturer at 170 hp @ 6250 rpm and it has a red line of 6750 rpm.
Check the numbers.
My feeling about the Subaru EJ-25 is that it shouldn't be pushed beyond
about 160 hp. However Subaru has a new 3.0-liter 6-cylinder engine that is
the same size and weight as the EJ-25. This is not the older 3.3-liter
6-cylinder engine. The 3.0-liter engine could probably make an honest 180
hp in an airplane. In a few years there may be enough of them to see a few
conversions.
It is good to hear that you are making good progress. I plan to keep a
close watch on the Jabiru engine developments. Best regards,
--
Roger Cole <rcole927@earthlink.net>
Elite 709
----------
From: Gregory Gordon <cosglo@ozemail.com.au>
To: murphy-rebel@dcsol.com
Subject: Re: Diesel engine option
Date: Mon, Nov 4, 2002, 3:49 AM
Dear Roger,
Like you I am building my tail kit, although my progress is moving along
nicely. I also have been thinking about an appropiate engine for my Elite. I
am not too "fussed" about a Lycoming, due mainly to the overall initial cost
and then the ongoing cost of parts. A month ago I flew from my home
(Sydney, Aus.) to Bundaberg, the home of Jabiru to have a look at their 6
litre, Jabiru 6600 engine. I was impressed. At this point in time, the
engine is been trialled in a 3/4 scaled experimental Spitfire aircraft. This
aircraft moves along at 200kts plus; but it is very early days yet. I was
advised that the factory will be trying out the engine in an RV 6 soon. The
packaged price is very good; The engine complete with starter, muffler &
dual electronic ignition is Aus$23,000; they will have a complete fire wall
forward component kit for the Elite/Rebel for Aus$5000; this includes
cowling, engine mount, oil cooler, propellor(fixed pitch wooden), spinner &
miscellaneous items. But I say again that it is very early days!!!
I have also looked at two Subaru packages based upon either a EJ-22(160hp)
or the EJ-25(180hp) using a SUB4 PSRU. The SUB4 agent here in Australia has
a new engine package based upon the EJ-25 and the SUB4 PSRU for about
Aus$13,000. Both these engine can easily be turbo charged. So there are some
good alternatives to the Lycoming.
Kind regards,
Greg Gordon. Elite 724E
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