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


Excuse me gentle people.  Has there not been extensive discussion on
this very list about the need to cool the incoming air/fuel charge by
use of inter-coolers to prevent all manner of undesirable results?
Heating the intake charge greatly reduces the amount of air/fuel that
can be ingested and burned in the engine with the associated reduction
in power.  It's called Boyle's law, not Boyle's suggestion.

I would also like to point out that boiling gasoline is difficult to
control and dangerous at best.  There is ample reason why such off the
wall devices have not succeeded in the market place, and it has nothing
to do with conspiracy theories involving oil companies and collusive
auto makers.  There is no such thing as a 100 MPG car that weighs in at
3000 LB and goes down the road at 65 MPH no mater what kind of
carburetor you put on it.  Hasn't happened yet, isn't going to happen
tomorrow.  If you want to fly behind an experimental petro-chemical
refinery do it on your own time and bandwidth.

Let us apply our efforts to more productive pursuits such at the wicked
cool planetary reduction that Paul has in mind, or a decent ignition
system that just works like the one driven off a sensor wheel mounted on
the E shaft, or the fuel injection system triggered in a similar
fashion.  Maybe after we have a fully functional and reliable system up
and running we can consider ways to improve the system by incorporating
simplification, reliability, and performance improvements.  Fix the
things that are broken, not the things that already work.

   Mark LaPierre

"It's called Boyle's law, not Boyle's suggestion."

I like that Mark. It is a great way of putting it.

Paul Lamar


Yes ,,, I like the last two contributions.

The beauty of a diesel engine is that it burns the fuel quite
efficiently, now matter how much gets dumped into the cylinders, and it
does this without a throttle-plate or tuned intake (I once even had a
diesel suck a white T-shirt into the intake and blow cotton shreds out
the the tail-pipe for a brief time - They will burn most anything! I
will not explain the idiot actions that were the cause of that :))

My understanding is that one of the reasons a diesel can run so
efficiently is that compression-ignition can ignite even the slighted
amount of fuel in the combustion chamber, and it is rather difficult to
"flood" a diesel.

Therefore ... finding an more efficient method to ignite the fuel
mixture in a gasoline engine is one reason I have often dreamed about
RF-powered spark plugs; ever since I first saw a Tesla-Coil running in a
physics lab 50 years ago and speculated that injecting a literal ball of
gas-plasma into the combustion chamber would be a great way to ignite
gasoline ...  Think of it as using a TIG welder to provide ignition
voltage.

R Bergland

You are missing something here Robin. Wet fuel in the recesses of
the combustion chamber will not ignite. It is too rich. You need
to heat it some how after it is in the combustion chamber hence
the hot rotor technique. In the diesel the hot air does the job.
The air is heated by compressing it. It is just not practical
to get the compression ratio high enough in a rotary engine to do
that.

We are also talking about two different things here. The fuel consumption
of the car and the fuel consumption of the aircraft engine. The aircraft
engine consumption is not a big deal as the BSFC is already .47.

However the car is running a BSFC of about .73 at cruise and the viability of
the rotary is at risk. It is far more important to fix the car first so
the rotary will stay around.

Paul Lamar