Eric,
Is that fuel burn ratio's 13.1:1 to 13.4:1 at WOT?
George (down under)
George,
13-1 at WOT is pretty close number. We will have more dyno, test
stand, and
in flight data in the coming months.
Eric Barger
I know this is probably picking nits, but I'd like everyone to think
about mixture (fuel-air) in terms %power (or best-power) instead of
throttle position (re "WOT" in this message). Throttle position -
especially on the rotary which runs well over a wide range of mixture
settings, is only a portion of the description or power output.
WOT should be thought of as "best volumetric efficiency" not "best
power" - though best power generally happens at WOT.
So, it sounds like Eric is saying that he sees his engines making best
power at mixtures around 13:1.
Side question Eric: Does your engine test setup allow easy inflight
setting/adjustment/control of the fuel-air mixture? As has been
discussed here in the past, this is critical for optimizing engine
performance (efficiency) lacking some kind of really smart FADEC system.
Regards,
Matt-
Matt,
I agree, I asked the question as I thought best power for the rotary was
12.65:1.
I intend running a carb with a wide band O2 sensor and a digital display
monitor/readout.
No good having a leaning knob, unless you can see what the fuel air ratio
is - my opinion only FWIW.
George (down under)
Matt,
Good input as it relates to VE and WOT. We tune our ECU using VE
correction
with a desired lambda as a base map. Our ECU has an external Barometric
sensor allowing for altitude comp without having to do any in flight
adjustments. One note about A/F mixture in a charged cooled rotary engine
the incoming A/F is cooling the rotor so you use this to provide cooling
as
well as desired and or optimum power. This is one variable we have that is
not in the Mazda rotary due to the oil cooling.
Eric Barger
Eric,
The charged cooled rotors may be a variable and I see it may be an advantage
in cooling - however I can't see any advantage in heated fuel for best VE.
In fact I would suspect VE to be down due to this design configuration.
What can you tell us about the pros and cons of charge cooling the rotor
specifically.
George (down under)
George, (down under)
There are surely tradeoffs in charge cooling, the advantages are no oil
cooling hardware, the VE goes up as load is applied due to the additional
Air fuel ratio passing thru the engine. The Charge cooled track and or
intake length increases the torque and flattens the torque in this engine is
flat from 3000-8000RPM. The path naturally atomizes fuel due to the passing
thru the rotor. Some of the above benefits are opinions and speculation due
to the inherent differences in our engine compared to the Mazda and the fact
that these above stated characteristics show a major difference in
performance characteristics out of a very similar sized engine 650cc/rotor.
I hope this provides you some answers.
Note: The engine loves cool air, full load, and alcohol as stated above the
VE gets better as you introduce anything that cools the rotor and or the
intake charge.
Eric Barger
Here is some early stuff I have on the engine.
--
Paul Lamar ...No rotor no motor.
BTW from the looks of the EGT curve there is a lot of unburned fuel in the
exhaust. I would pump more hi pressure air into the exhaust and build a
turbo compound
configuration to get the best out of this engine.
Also Eric look into making the e-shaft out of hydro formed thick wall 4340
tubing.
It will save you a lot of machining cost.
--
Paul Lamar ...No rotor no motor.
These old sweep tests, pictures and drawings are from the previous group and
are not accurate. We have all the above on our website and will begin to
update it with our GEN II engine release and also we will begin to have
third party testing and validation to support any numbers. The EGT in our
engine never runs over 1550 or so, this 1701 plus again is from an old pre
RotaMax Ohio testing group.
Eric Barger, President
Phone 419-694-3000 x 222
RotaMax Inc.
15152 Twp Rd 190
Arlington, OH 45814
Fax 419-694-1401
www.rotamax.net
Here is another tidbit of information you might be interested in. Could save
you some heartaches down the road. The Midwest, now Diamond, engine also uses roller
bearings on the rotor. They are not a charged cooled rotor design but they
are an air cooled rotor design. Roller bearings are necessary as both engines do not
use a pressurized oil system to feed oil to plain journal bearings. Air is physically
pumped through the Midwest rotor to cool it. This pump consumes HP so the BSFC is also
impacted.
What Midwest found out was the roller bearings had to be hand fitted at close
tolerances as non uniform G forces were acting on the rollers. These forces caused
skidding of the rollers with early failure. Here is a sketch of what goes on.
Paul Lamar
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.
