frank barbot wrote:
Hello,
I am working on engine conception (and a part of production) for
7
years, in
the past on gasoline and automotive and aeronautic applications.
I am now working for Mistral engines, with a base of Mazda
rotary
engine
13B
for aeronautic application.
So i would like to participate to your discution as a member.
I already do have a question.
The oil going to the head of rotor and apex seal coming from the
"secondary
volumetric" oil pump, through oil injectors, is mixed with air
coming
from
the inlet manifold. When is this flow usefull, what is his
fonction,
can
i
suppress this in certain condition ?
This question is very important for me, i am dimensionning a new
lubrification system dedicate to our application on that
function.
Best regards
Frank BARBOT
Welcome Frank. I'll repeat what I just said to Francois.
I don't have much on the pneumatic part other than what is in the
shop
manuals which is also not much. Mainly checking the one way
valves.
I think they function when the pressure is lower in the intake
chamber
than atmospheric. As far as I know no positive air pressure is
used
to assist the oil injection. Mazda main thrust on the design is
to reduce the quantity of apex seal oil as much as possible to
reduce emissions. A small positive displacement pump may be all
that you
need. Use a separate tank for the 2 cycle apex seal oil with a low
oil
warning light.
Here is one I made quite some time ago. I used off the shelf gear
pinion
stock for the rotors.
Paul Lamar
Frank,
I don't know if what I say will contribute anything BUT someone on
this
discussion group ( I can't remember who) said the 'oil metering
pump' was
a
two stage pump with a small amount of oil in Idle and fully on
(100:1)
just
above idle.
This may be different for the later Series 6 and RX8 models as they
are
electrically controlled metering and as Paul said the emphasis was
on
emissions control. Personally I would measure the out put at
different
RPM's, while running the engine on pre-mix.
Now having said all that, a recent trip to my local engine builder
mates,
informed me that they couldn't put an aftermarket engine management
system
on a Mazda, without first replacing the 'oil metering pump' with an
earlier
model manual pump- why! because there wasn't a Engine Management
System
manufactured to cater for 'oil metering'- why! because no other
engine
required this facility and it was a system for Mazda alone.
Is this the case with the Mistral Engine Management System?
George (down under)
Frank's job is to design the system for Mistral.
Paul Lamar
Mistral's DEM system can electronically manage electro-valves
precisely
metering the oil. Frank wants to know if he can do away with the
pneumatic
system in this set-up. I must admit we don't know as we have not
worked on
this system so far because it works fine... except that it's bloody
expensive to manufacture and to install (we are talking of copper or
steel
lines replacing Mazda's nylon line Paul "loves" so much for their
durability! :-) ).
Cheers
Francois (across the pond)
I looked it up in the RX8 Service Highlights manual. Ironically I have
more info
on the RX8 than any other 13B. The function of the atmospheric air
supply
and the one way air valves in the injectors is to prevent the intake
chamber from sucking
oil out of the injection lines when the pressure in the intake chamber
is below atmospheric
which will happen big time if the throttle is closed while the engine is
still turning at significant RPMs. Definitely an emissions issue.
Probably
not a problem in an air craft engine. If the the oil is mixed with the
fuel
before injection that too would solve that problem. In other words no
direct injectors.
The PCM changes the electronic stepper motor metering pump according to
engine speed, engine
coolant temp and the amount of intake air. The fail safe mode is; the
injected
amount of oil is minimized and oil is injected only according to engine
RPM. The failure
of the stepper motor can be sensed by the PCM. The PCM then limits the
amount of
fuel and hence the RPM and the power the engine can generate. Again a
fail safe
emissions issue since too much apex seal oil does nothing except
increase the
Hc emissions. In other words a limp to your car dealer mode :)
Aren't computers wonderful? :)
Paul Lamar
Ben Schneider wrote:
I don't know too much about them, but how does a 2-cycle oil injection
system work? (as on a snowmobile) Would something like that work, as you
would still have a seperate oil tank, but it mixes with the fuel before it
enters the engine. Perhaps more simple, and maybe less complicated? Just a
thought.
Ben Schneider
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