The rotary engine suffers from high BSFC at low loads.
   Low loads are the name of the game for automotive engines.
   GM found back in 1978 that the temperature of the rotor face had
a strong   effect on the low load BSFC. A 9.8% improvement in the
BSFC   was possible with a hot rotor at low loads. Higher rotor
temperatures gave   lower fuel burn at low loads. However if the
rotor was not   cooled at high loads the cast iron over heated.   GM
got a patent in 1976 on a hot rotor face insulated from   the rest
of the rotor. Here is a pdf on the 3,995,602 patent.   The SAE GM
paper on the subject was 780419.

   The obvious solution is to control the temperature of
   the rotor as a function of the load on the engine.

   The amount of oil cooling on the rotor is now controlled
   by a ball and a spring that opens at a certain RPM.
   RPM is not the problem. Engine load is the problem.
   A way can be found to cut off the oil cooling to the
   rotor at low loads regardless of the RPM. In other
   words run the rotor face as hot as possible at all RPM's.

   One mechanical way of doing that is insert a stationary tube
   in the center of the e-shaft that moves back and
   fourth controlled by a servo that senses engine
   load and cuts off the cooling oil supply to the
   rotor. A peice of cake for todays computer controlled
   engines. In fact it need not be controlled by a computer
   or electrical servo but by a simple air servo connected to the
   intake manifold pressure.

   Patent applied for :)

   Paul Lamar

   Sounds like it should work ... however ...

   Common sense (which often fails me) tells me that something else
is   really going on in during the compression/ignition cycle that
is not   addressed by the GM research. I find it hard to believe
that somehow   the gas charge "knows" about a 100 degree temperature
difference in a   metal surface that is whizzing for the briefest
instant during the the   ignition/combustion process. It all happens
in about 0.01 seconds. By   far the majority of the the gas-charge
is separated from the rotor   surface by only only a fraction of an
inch, but this fraction of an inch   amounts to millions of
molecules of separation. That seems like miles to   me in my
microscopic world-view. And the theory is that what would   appear
to be a barely significant temperature difference in the middle   of
a thermodynamic inferno is going to somehow extract 10% more energy
 out of the reaction ?????? I dunno???

   In defense of the theory, the operation of glow-plugs come to
mind, and   of course, pre-ignition due to a build up of combustion-
chamber deposits   can really affect the fuel burn. But these
examples relate to very high   temperature surfaces. Back about 1970
I had a little Ford Bronco that   would start running really rough.
A few times I was forced to pull off   onto the shoulder of the road
and remedy the situation by dribbling   coffee from my thermos
bottle down the throat of the carburetor as I   raced the engine to
help the beast "clear its sinuses".

   So yes, combustion is/can be influenced by surfaces, but at 300
   degrees?

   I have often wanted to experiment with extremely high-voltage, perhaps
   radio-frequency spark plugs. (RF currents are not dangerous to
humans,   since the molecules in our bodies are to sluggish to
respond to the   signal as they do in direct currents.) So by
applying a huge RF voltage   between the upper and lower plugs one
might be able to get very   efficient ignition to occur. The design
problem I have not yet solved   is what the nature of the combustion
chamber and rotor surfaces would   need to be to force the RF
electrical discharge to either arc across the   surface or create a
blast of plasma through the gas-charge rather than   jump back into
the housing metal for part of its journey to the other   spark plug.
Ceramic engines? Maybe.

   Patent soon applied for :)

   R Berglund

   There a lot of other things discussed in the SAE GM paper but
those, in the   opinion of the GM engineers, could be addressed with
high pressure direct   injection. It had mostly to do with the raw
fuel wetting the walls of   the combustion  chambers including the
compression chamber and the exhaust  chamber.   Mazda addressed some
of those issues with the RX8 and how it recycles   raw fuel with the
side exhaust ports.

   IMHO it is just a matter of time before this problem will be solved.

   Paul Lamar

     Cell phones are 900Mh, Virg

  Here is how to have your modified 2.5 rotor RX8 get 50 MPG at a
steady 65  MPH using an AIXRO one rotor kart engine mounted on  the
back of the stock RX8 differential.

  First read this. http://www.rotaryeng.net/RX8-TC-eng3.html

  Here is a cheaper and quicker way of testing this concept. Get an
AIXRO Kart  engine and mount it on the back of the RX8 differential.
Remove the stock  rear cover. Use a second pinion gear and run the
AIXRO only at cruising  speed with a one way clutch to disconnect it
at lower speeds.

  Assume 30 inch tire. That is 94.248" circumference so that is 7.85
feet in  circumference. At 95 feet per second or 65 MPH that is 12
revs per second or  720 RPM times 4.77 is 3434 engine RPM.

  So you need a 2.17:1 planetary reduction given 7452 RPM for the AXIRO
  engine. That is
  also 114 revs per mile per hour or 96 MPH at 11,000 AIXRO max RPM.

  BTW for those on here that have not yet heard a Mazda 13B 1991
Turbo II  engine  more or less stock went 229 MPH at the recent Reno
air races in a RV6  experimental  airplane.

  Paul Lamar

  Hi Paul,

   I happen to have a very good friend across the Pond (remember, I
am in  Europe) who is running a prototype rotary engine on extremely
lean burn with  Dynamic Spark Ignition. Somkinda radiofreq you know.
BSFC is extremely low  but confidential information so if I tell you
I'd  have to kill you. I won't  do that. Very low BSFC indeed. But
today is Christmas: put your spark plugs  to rest and light up your
candles. (Funny: in french they are both called  "bougies").

  I wish you a merry Christmas Paul . And I wish merry Christmas to
all the  readers (and contributors in particular) of Rotaryeng.net

  Randolph in Paris

  Microwaves can boil water. Why not fuel?
  Brilliant idea.

  Paul Lamar
  --

   Smokey Yunick did some sort of fuel boiling thing years ago,
 pumped the   exhaust from a V-8 back up through the intake manifold
to really heat   things up.  Made all sorts of power and economy
claims for it but then I   never heard anything more.

   Hmmmm, I knew Google would find something:
   http://www.rexresearch.com/yunick/yunick.htm

   Anybody in the group who can shed some light on this?  Could it be
   applied to a rotary engine?

   SD

  I think it needs to be boiled in the combustion chamber. I think
hot  Mixture would merely condense on the cold walls of the intake chamber.
  Mazda already heats the intake side of the rotary engine.

  http://www.sbir.gov/sbirsearch/detail/72100

  www.rotaryeng.net/Adiabatic-rotary.pdf

  abstract:

  A CONSIDERABLE AMOUNT OF R & D WORK HAS BEEN DONE FOR THE WANKEL ROTARY
  ENGINE APPLICATION TO AUTOMOBILES, PLANES, ETC. RESULTING IN SIGNIFICANT
  PROGRESS. THE PERFORMANCE, RELIABILITY AND DURABILITY THAT THE
WANKEL HAS  DEMONSTRATED, HOWEVER, FALLS SHORT OF THE POPULAR DIESEL
ENGINE. THE  ADIABATIC, TURBOCOMPOUND CONCEPT THAT HAS BEEN
DEMONSTRATED FOR THE DIESEL  IS THOUGHT TO BE MORE BENEFICIAL TO THE
ROTARY ENGINE. PHASE I IS CONCERNED  WITH AN ANALYTICAL STUDY OF AN
ADVANCED WANKEL ENGINE WHICH WILL INCORPORATE  ALL THE ESSENTIAL
FEATURES OF AN ADIABATIC DIESEL ENGINE. SOME OF THESE  FEATURES
INCLUDE EXTENSIVE USE OF CERAMIC WEAR COATINGS, TURBOCHARGING AND
COMPOUNDING, HIGHER COMPRESSION RATIO AND FASTER COMBUSTION.

  Roy Kamo

  www.rotaryeng.net/Adiabatic-rotary.pdf

  There is also a group in England working on an adiabatic rotary.
  http://ceramicrotaryengines.com/

  One thing that has not been tried to my knowledge is
  bringing out the  exhaust a considerable distance
  from the  exhaust ports to further heat the intake
  side. You do this with a valve that blocks the normal RX8 eng.
  side exits and diverts the exhaust only at low power levels.

  Paul Lamar

Had the enjoyable experience to sit and talk about many
unusual engineering devices some years ago at Sun-n-Fun,
with retired engineer John.

One was the Pogue carburetor which totally vaporized the
fuel charge.  Claims of 100 MPG.  do a google search

John commented  that if you heat gasoline to 1240F (?) or more
the vapor WILL NOT condense back to a solid, which the Pogue
did by using exhaust heat. Any solid droplets were recycled
until vaporized...

  How would we utilize for a Rotary?  How about wrapping the fuel
line around the exhaust pipe and using a propane "carburator" as
a fuel mixer?  Too much risk for an unplanned explosion?  How to
get the engine started in the first place?

Dan F


You could start on liquid fuel. There has been people try the coil around the
exhaust and in a can with exhaust through it. It is hard to get the fuel ratio
correct. You would also have to use a silicone diaphragm in the mixer. They
are available from Impco. The problem is to keep it in a vapour state. Also as
Smokey described, a homogenous mixture is required to keep detonation at bay.
To much heat in  the intake and the density is reduced which kills power. To
get power and economy Smokey's system needs to be experimented with. I see no
reason it would not work on a rotary engine. Gasoline needs to be heated to
about 450F to totally vapourize. There has been people try putting a tube in
the gas tank and using a carb without fuel as the throttle for the fuel vapour
for mixture ratio bolted on the fuel tank. A hose then ran to the carburettor
air filter to supply the fuel. Good mileage reports but eventually the tank
was full of heavy oil like diesel. The vapourization point for it had not been
reached so it stayed in the tank. Gasoline is a witches brew of hydrocarbons.
some vapourize readily at room temp and some require 450F, the rest are
somewhere between.
For AC use the economy increase sounds great. The extra heat under the cowl
needs to be contained or distress to resins is going to be a problem. This
increases weight. The weight could be offset by the reduction in fuel
required. Also remember the intake manifold is required to be surrounded with
a heat muff with exhaust gas to achieve the final intake temp of 450F. Carbon
build up in the heat muff and carbonization in the intake manifold would need
to be monitored.

Dale Davies