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Originally Posted by Rotary10-RV
John,
I speak only with regards to Mistral here, you are simply wrong. They are certified the engine. The FAA would be a bit upset about misleading fuel claims in a POH. I'll give you the benifit of the doubt here and say your comments are made in ignorance, rather than being malicious. I have followed the development of Mistral's engines on several rotary oriented sites and they have been very up front about how they improved the fuel flows and the HP in their engines. Some of the changes they made that ran counter to the "accepted wisdom" as well. Their willingness to share their dyno results has been a great help. That Mistral has agreed to sell some of their very well made parts to homebuilders, (and more importantly DELIVERING those parts), speaks volumes about the quality of their organization.
Bill Jepson
Rotary10-RV
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Bill, I appreciate you and your comments but show me. Promise from an engine supplier for aviation is like a used car salesman with a bad combover and plaid jacket, no offense to Mistral. Their intentions and integrity may be without question, but promises are made to be broken to rock a tired cliche'.
They claim or hope to certify their engine, it has not happen as far as I know and are not making breath taking headway. In fact it may never happen. I hope it does, but if it does not happen, that would be par for the course. Also they promise that they will sell parts to homebuilders means....... what? More promises. The landscape is littered with the latest greatest engine to every fly, that never did. Again not taking a shot at Mistral, only the history of their for bearers in this business. The track record is so poor I would advise NO one buy into any unproven engine package until it is flying and tested, with independant flight test (Van's, Cafe Foundation). If it was good they would invite outside parties to verify their numbers. That will not happen I predict.
Sorry if I sound paranoid, but "You are not paranoid if they really are out to get you."
Also they will have to "certify it" in an airframe, a certified airframe, all good but I think they are way off from that.
Reality check on fuel economy. The Mistral is based on Mazda parts as far as I know, nothing NEW or unique, a Mazda Corp rotary engine, with some external changes or mild porting or modification. Never the less the basic design is Mazda. I don't know of ANY Mazda claiming as good or better fuel efficency. In fact they Wankel is inherently terrible. They have a long way to even get parity to a Lycomimg despite their claims.
The Mazda does OK with fuel economy at altitude in the Teens with a turbo. So if you are going turbo (I would with a Rotary) and always fly in the supplemental O2 breathing altitudes you might get close to Lyc fuel burns. However takeoff and climb you are going to still pay a price.
I suspect their claims are enthusiastic (hopeful). They allude to improving the aerodynamics of the installation package, but sounds like excuses. When ever I hear
actual Wankel fuel burns, actually measured by independant party, they are high. This is always followed with excuses and talk from Wankel'ers about "Oh well the ECU was not optimized" or other such nonsense.
The fuel economy of of a Wankel engine is deep within the basic and inherent design. Take a RX8 late model sports car, the only Wankel vehicle you can buy today. A friend has one: Gets terrible actual gas millage (reported EPA milage, reported 5 MPH less than equivalent 220HP sports cars both city/hi-way and his does not get that), Oil Burn - about 2 qts (into injector) between oil changes (he actually caries oil bottles in his care, I can't remember when I added oil between changes to my cars). Again Wankel fans will say the ECU is not optimized.....please the engineers at Mazda did every thing they could to get the best milage it could get. The sports car with similar gas milage 18/23 is the Nissan Z-car with 80 HP more. Facts are facts.
It may be turn of the century technology but 4 cycle Otto cycle internal combustion piston engines are fairly efficient compared to anything else. (Actually they are all inefficient but that is about the best we have behind diesel.)
The Wankel rejects (wastes) such hot high speed gas, it's suited for a turbocharger. However that adds complexity and weight, whose benifit is best exploited at high altitudes. That's not how I fly in my RV (local, acro, formation and 20% high cross country). In a RV-10 may be a better choice if all you do is fly high with O2 bag on your face or up the snaazola. Of course you can turbo a Lyc. Look at the new Mooney or Piper Malibu and their FL250 dual turbo, inter-cooled Lyc performance. High compression and turbo charging is a way to add efficency. I have lots of past experience with turbo planes flying freight and CFI'ing. Let me just say, I am glad I did not own any turbo plane. The turbo was a big maintenance item. It was a neccessary evil for performance. There's no such thing as a free lunch; you have to pay for performance. The idea of cheap alternative engine with turbine power is a dream. The famous aerodynamic principle of lift and speed is a function of money is pretty true.
I don't understand folks denial of actual rotary engine fuel burn numbers. Time and time again the facts and flight test show that the Wankel is thirsty. It's a technical marvel, but gas economy is NOT its strength. The other down side is oil use and noise. Other than that, they are cool.
Personally I don't care for ECU's but Tracy I recall has tried to address this with a redundant ECU unit he sells. Nice engine but no econ engine? NO. Mistral redundant ECU looks very and aerospace quality. Hat off, what I see is nice, no doubt.
I doubt Mistral can make a breakthrough in gas milage with basically a stock Mazda design. Even if they started from scratch, the design and principles of the Wankel to date are such they burn more fuel per HP. Unless there's a radical improvement to Dr. Wankel's design, it ain't going to happen. Again fly high and turbo charge you Wankel's to get the best possible fuel burn, but down low not so good (by a significant amount).
No offense or desire to rain on any one's parade intended, but that is they way I see it after watching the progress of Wankel's for +30 years. Just a piece of wisdom, don't fly behind a power plant or components that have not been shown reliable. Even Eggenfellner and RWS rotary engine parts have a track record, Mistral? Hope they do what they say, but I would wait. To date the best "engine conversion" is converting +$20,000 for a Lycoming (+$30K for RV-10 builders).
See ya there!
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