|
Here we go again!
Personally I think you cannot directly compare the
piston to the rotary.
However, what do you want?
a) Compare chamber volume?
b) Compare swept chamber volumes for one "stroke"
or all "strokes"?
c) Compare pumped volume per
crank-revolution?
d) Compare pumped volume for every chamber-once (6x
for a 2-rotor)?
e) Tracy, you are only partially right, now let's
talk 2-stroke piston: a 1-liter 2 stroke is still a 1-liter engine, allthough it
will have twice the power (in theory) as a 4-stroke (...and pump twice the
volume, but it still is a 1-liter)
Granted, the 4-stroke will pump the same amount,
but only pumps half of it out, the other half gets compressed and expands again
in the same cylinder...
f) Compare it 4-stroke or 2-stroke?
g) Want a good tax-measure, Mazda did
it!?
So, one would have to really go and define on what
basis you want to compare what....
I think the only real value to us is, how much
fuel/air does it use per time-unit to make horsepower and how much does it
weight while doing this and how long does it last?
E.g.: How much power does it make for how long with
20 gallons of fuel, compared to a piston?
Don't care about displacement/rpm/PSRU
etc.
Anyway, there is no doubt:
Rotaries rule!!
period.
Thomas J. :)
----- Original Message -----
Sent: Wednesday, March 22, 2006 4:54
PM
Subject: [FlyRotary] Re: Rotary - FWD
from Lancair ES List
Hi Mark,
Glad you are there to represent the rotraries. Sounds like the
usual misunderstanding about the displacement of the rotary is in play
there. Try to get them to understand that the displacement of a rotary
is rated in terms of the volume of fuel -air mixture that is burned
in 1 revolution. The piston engine takes 2 revolutions to do
burn its rated displacement. This makes the 2 liter 20B equivalent to a
4 liter piston engine. That is the source of Gary's HP calculation
error.
Tracy Crook
----- Original Message -----
Sent: Wednesday, March 22, 2006 11:59
AM
Subject: [FlyRotary] Rotary - FWD from
Lancair ES List
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
>
> ---
bjburr@mwheli.com wrote:
To Post a message to
the group, send it to:
Lancair_ES@YahooGroups.com
To Unsubscribe, send a blank message
to:
Lancair_ES-unsubscribe@YahooGroups.com
If you have questions for the group administrator, send
it to:
Lancair_ES-owner@YahooGroups.com
YAHOO! GROUPS
LINKS
--
Homepage:
http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net/lists/flyrotary/
|