Once a month SZP opens the airport for visitors. Those of us with
unusual air planes open our hangar doors and people stroll by and ask
questions. Many are questions I have heard over and over again.
The rotary powered RV4 with the cowl off is prominent and draws a lot
of people,
I am scheduled to give a talk about rotaries at AusFly in Narrowmine NSW
Aus next week. To speed the process I am getting a large poster printed
with some of those questions.
Here is a preliminary version. Comments are welcome.
Paul Lamar
Paul,
You know far more about rotary engine durability than I do, but you
continue to bury your head in the sand when it comes to the fuel
efficiency of rotary engines--at least when it comes to cars. The fact
of the matter is that rotaries use 20-30 percent more fuel than
comparable, modern piston engines. That's why even Mazda has given up on
them. The proof of this is incontrovertible and as a rational engineer,
you should accept this fact. That shortcoming doesn't disqualify the
rotary as an aircraft engine, where its other virtues--light weight,
compact size, smoothness, and durability--might be more important.
Csaba Csere
The BSFC is now within 5% of a piston engine
The car problem has more to do with the gear box chosen by Mazda than
the BSFC of the rotary.
My RX8 is doing 3000 rpm at 80 while my 250 HP Honda Odysseys is doing
1800 RPM. This the same reason the 400 HP Corvette gets 25 MPG on the
free way. My 1994 Mercury Cougar was doing 1900 at 80 MPH.
At a steady 70 MPH the RX8 is getting 25 MPG. The same as my old RX2 and
the two RX7s I have owned. All had the wrong gearing.
All you need do is look at the OBD data attached.
Another factor is when the Mazda computer leans the engine and when it
does not. Leaning improves the BSFC. Honda circumvents the NOX
emissions laws by not leaning the engine during the smog test. The rest
of the time they lean it frequently. Nox is a big problem for diesels as
nox increases when running lean. Mazda never leans the RX8 engine no
matter what.
I have developed and patented a high speed MSD ignition system that I
hope will knock a few points off of the BSFC.
The exhaust valve, in a 4 stroke, waste 20% of the of the recoverable
energy in turbo compound use. The exhaust normally waste 50% of a gallon
of gas. Harvesting in F1 speak. A turbo compound rotary would therefore
become the most efficient IC in the world maybe short of some diesels.
The F1 hybrid scheme is not the most efficient for free way use,
http://www.rotaryeng.net/Oxford-TC-talk.mp4
If Mazda does not build a turbo compound rotary they are not informed.
Mercedes, Renault , Ferrari and Honda will.
We now have a RB 650 HP 2 rotor that weighs less than 200 pounds in a
time to climb project air plane. It has a controlled leak in the exhaust
manifold because there is too much energy in the exhaust. In other words
it would over boost the engine. This is in addition to the waste gate.
Mazda ought to hire me as a consultant. I would straighten them out damn
quick :-)
Paul Lamar
Paul,
The rotary has relatively short gearing because it has little low-rpm
torque and if the gearing were any taller, it would have no acceleration
in top gear--at least with a manual. Most of the other cars you quote
are non -porting and have automatics, so they kick down when you floor
the accelerator.
Also, there are other cars with similar gearing to the Mazda, such as a
BMW 335i. But that car gets better mileage--over 30 mpg at 70 mph--while
delivering far more performance--in a much heavier car.
As to the Honda leaning out during off-cycle driving, I don't know what
your car does, but such a calibration would be highly illegal and I
doubt that Honda, or anyone else, uses it.
Your turbo-compound rotary idea has merit, but it says nothing about the
efficiency of real-world rotaries.
Csaba
Of course. It does need an automatic manual. (Computer controlled hyd
shiifting}.
30 MPG verses 25 MPG is 20% not 30%.
My neighbour has an M3 and I will ask about the 80 MPH RPM.
The piston engine has millions of more hours of R & D.
Due to new apex seal materials the leaning angle can be increased
allowing a higher compression ratio or a better combustion chamber
shape.
I had the OBD II on the Honda and I saw a lot of situations where it went
way lean. The gov only cares about the arbitrary driving cycle and
they don't peer over the shoulders of the company EFI programmers.
From a software point of view it is easy to detect the silly driving
cycle.
The nox v BSFC situation was discussed in Bruce Briggs book War against
the Automobile.
Paul Lamar
What is not real world about turbo compound. CW made thousands
of R3350 TCs. A Super Connie could stay aloft for 24 hours.
Actually the exhaust valve was the Achilles heel. The head would
come off and take out the turbine. Rotary no problem no exhaust
valves.
Paul Lamar
"As to the Honda leaning out during off-cycle driving, I don't know
what your car does, but such a calibration would be highly illegal
and I doubt that Honda, or anyone else, uses it."
Csaba Csere
Hey Csaba, Looks like VW was caught doing just exactly that.
See the attached jpg.
Paul Lamar
Paul,
VW sure stepped in it and I think the EPA will make an example of the
company. As I pointed out, using different calibrations on and off the
emissions cycle is illegal. It was illegal when I worked at Advanced
Engine Engineering at Ford 35 years ago. I bet the Feds will be looking
at their gasoline engine calibrations as well.
There will be many opportunities for promotion in the VW organization
before this is over.
Csaba
P.S. I think that graph is for gasoline and not diesel engines. It's
also an old one. I don't think that HC rises so quickly with lean
mixtures anymore. Lean burn is now more stable with less misfiring and I
think it's possible, with an optimized engine to run leaner than 20 to 1
without misfiring.
----------------------------------------------------------------------------
The EPA rules on emissions need revaluation in light of MPG
issues. Perhaps that will happen if we get a president that
can think.
The rotary is particularly good at running lean. Apparently, due to
the rotating combustion chamber, the heavier fuel molecules are thrown
out towards the spark plugs. Running lean is very noticeable on lower
fuel burn in rotary aircraft use.
My hangar neighbour Klaus Saviour runs his piston engine at 50 degrees
advance and 18;1 at high altitude. (low manifold pressures) He holds
some MPG records in air craft at around d 52 MPG at well over 100 MPH.
He builds and sell the LES ignition.It is a multi-spark but very
complicated. I have no real details on how he does it.
Mine will spark six times every 5 degrees at 10,000 RPM. As you are
well aware that is harder to do with a rotary as each rotor fires
every rev while a 4 stroke piston fires every other rev.
The MSD is limited to 4500 RPM on a 4 stroke piston.
We are in competition but mine is much simpler and cheaper to make.
Here is a short video. Patent pending.
I am in the process of getting mine flying as well. We were going
to demo it in Australia at Ausfly but last minute problems with
the engine simulator prevented that. Then Robin got sick (no pulse or
blood pressure) with a rare disease and nearly died so we were stuck in
Oz for an extra week until she got better enough to fly home.
If you are in Ca around the 25th of Oct you are invited to our
25th wedding anniversary party.
Paul Lamar
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