Hey Guys,
I thought I
would forward a post from the Lancair ES list concerning rotaries
(oldest post on the bottom). There are very few rotary powered
Lancairs, so I’m kinda the front man on this one by default. I may
come to some of the Fly Rotary “experts” for help if I get in a corner,
but so far, everyone’s been polite and its been a fun exchange.
I’m sure there
is more to come.
Mark
Steitle
Lancair ES –
N/A 20B
From:
Lancair_ES@yahoogroups.com
[mailto:Lancair_ES@yahoogroups.com] On Behalf Of Mark R Steitle
Sent: Wednesday, March 22, 2006
8:41 AM
To:
Lancair_ES@yahoogroups.com
Subject: RE: [Lancair_ES]
Rotary
Gary,
First, it is
not my intent to flame you or anyone else. I only strive to
educate. I don’t know just where your calculations are off, but
obviously something is amiss. Mazda rated the N/A 13B 2-rotor
engines anywhere from 160 to 180 hp. The 2.0L 3-rotor was only
produced in a turbo model (20B-REW) and was rated at a very conservative
299hp. The new RX-8 Renesis engine (a 1.3L n/a 2-rotor) is rated
at 238 hp.
Attached is a
hp/torque chart from the Mazda 26B 4-rotor engine that was used in the
Mazda LeMans race car, and won the LeMans in 1990. It shows that
it produced 675hp at 9000rpm. That is over 150 hp/rotor.
While this engine was a peripheral-ported engine, it also was
normally-aspirated. Mazdatrix recently dyno’d a N/A
peripheral-ported 13B for Paul Lamar at 250hp @ 6000rpm, running a
carburetor. That is an easy 125hp/rotor, and 250 hp from a 195#
engine. (While 6000rpm might sound high, keep in mind that the
crank turns 3X the rotor speed. So, when the crank is turning
6000rpm, the rotors are only going
2000rpm.)
Also attached
is a dyno chart by Atkins Rotary showing a turbo 3-rotor producing 375hp
at 6200. This is in the rpm ballpark of where you would normally
operate a rotary airplane engine running a 2.85:1 gearbox, such as the
RWS model RD2-C. It should be noted that the rotary’s lowest
bearing loads occur at 5900 rpm. So, 6200 is very close to the
“sweet spot” as far as bearing loads are concerned.
Turbo’d
rotaries can produce an incredible amount of power for their size.
500hp from a turbo-charged 13B in not all that unusual. That would
correlate to 750hp from a 3-rotor at the same boost. So, 580hp at
7000 is well within reach of the common man. A Velocity builder in
California (Al Glitzen) recently
dyno’d his N/A 20B at 275 hp @ 6000.
In the early
days of the rotary, they were beating the pants off of all the
competition, so the SCCA came up with an equalizer formula to make
racing fair for all participants. It effectively doubles the 1.3L
displacement and treats it is a 2.6L. If you compare the airflow
of the 1.3L rotary engine it pumps as much air as a 2.6L 4-stroke piston
engine would. So, the SCCA considers the displacement to be 2.6L
for the 13B and 3.9L for the 20B. Maybe this helps explain why
they produce more hp than your calculations would
indicate.
As you pointed
out, one of the most attractive features of the rotary is its soft
failure modes. If they’re running when the failure occurs, they
will usually keep running until they are shut down, then they will
refuse to re-start. The 13B has only 3 moving parts, two pistons
and a crank. Pistons are cast iron and the crank is
bullet-proof.
For more
information, check out the ACRE (AirCraft Rotary Engine) web
site at www.rotaryeng.net.
Mark
Steitle
From:
Lancair_ES@yahoogroups.com
[mailto:Lancair_ES@yahoogroups.com] On Behalf Of Gary Casey
Sent: Tuesday, March 21, 2006 10:06
PM
To: Lancair_ES@yahoogroups.com
Subject: Re: [Lancair_ES]
Rotary
I should
probably take this to the rotary engine list as they seem to
have napalm ready to flame us "disbelievers", but
here goes: A
naturally aspirated 2-liter Mazda engine, according
to my
predictions,
would produce about 160 hp at 7,000 rpm. Under boost,
and I don't know whether
this one is running 39 inches (Hg?) manifold
pressure or more likely 10
psi boost, which would be about 50 inches
Hg, I would predict a power
output of 275, maybe a little less. This
roughly correlates to 275
hp for the last twin-turbo RX7, which ran
to about 8500 rpm.
The claim below is 580 hp, or twice my prediction
and about twice the best
specific output from Mazda. And then the
580 hp at 7,000 would be
equivalent to a torque of 435 ft-lb, which
is higher than the peak
torque stated (386 ft-lb).
All that is not to say it wouldn't make a good engine
for the ES. It
would tolerate 50 inches of manifold pressure and
7,000 rpm quite
well
and that would produce 275 hp. With some effort the turbo
setup
could be
matched to give a critical altitude of 10,000 ft. Power
would probably fall off to
maybe 200 hp at 20,000 ft, still
respectable. The thing that always bothered my
about the rotary
option is the relatively high fuel consumption, maybe
10% higher than
a
piston engine. The thing that is attractive is that there
are
very few
catastrophic failure modes. They will keep running with a
broken apex seal and even
with no coolant.
Gary
Casey
On Mar 21, 2006, at
9:30 AM, <fpbjr2001@yahoo.com> wrote:
> ed
> the rotary is a 20b. a 2 liter or
120 cu. in.
>
engine.
> we have an IVO
prop on it to get us through the 40hr
> test. we are going to look at the MT prop at
sun-n-fun
> and we have a
prop that chuck diaz has designed for
> the rotary community. we are going to ground
test it
> before another
guy flight test it.
> paul
brannon N117ES
>
>
--- erosiak@comcast.net wrote:
>
>> Paul,
>>
>> What is the cubic inch engine size of the
rotary,
>> and what
prop will you use??
>>
>> Ed Rosiak
>>
>>
>> -------------- Original
message
>>
----------------------
>> From:
<fpbjr2001@yahoo.com>
>>
>>
>>
>>> From:
<fpbjr2001@yahoo.com>
>> To: Lancair_ES@yahoogroups.com
>> Subject: RE: [Lancair_ES]
Someone talk some sense
>> into me!
>> Date: Tue, 21 Mar 2006
15:22:13 +0000
>>
>
>
---------------------------------
> bryan
> no! no! we hope to be a little
better than piston
>
speeds.
> we
did dyno the engine. 39" mp (10 lbs boost) it
> made 580 hp @7000rpm and 386ft/lb torgue @ 5400
rpm.
> we will
turbo normalize with 3 lbs boost or 33" mp
> and make about 330-350
hp.
>
paul brannon N117ES
>
>
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