Hi Mart and all,
I am as well informed about Rotaries in aircraft or aircraftuse as roaming 2 forums about the matter permits.
At this time (unfortunately) no practical experience with Rotaries yet....
I only dismissed Rotary fuelburn as a concern comparing it to pistons.
Mistral matched and bettered the equivalent Lycoming numbers. Mistral published their dyno numbers to max. power. Lycoming stays quiet above 75%.....
Though the Rotary used to use more fuel, this is not true anymore. The RX-8 is at least even with the competition.
What I hear it is just incredibly hard not to floor the pedal and hear+feel the engine!
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You control the consumption and fun!
However the Renesis was specifically made for the RX8 and it seems Tuners/Racers have a hard time to find extra horses without a Turbo. The exhaust is too restrictive.
As the Renesis was developed for the road it surpassed fuel-consumption and emissions requirements for 2005 already in 2002.
So there is no real disadvantage anymore in that regime.
Of course the aviation rotary - Mistral - will be a totally different animal than the car version (Mistrals principal engine dimensions are identical with Mazda, although by today there are no interchangeable parts anymore....).
I think the last car that tried aircraft engines was Tucker - tried to use a Lycoming or a Franklin.
Can't really compare aircraft pistons with car engines either....
If you want to get detailed about displacement definitions, I recommend to visit Paul Lamar's site mentioned somewhere in my last posts.
There is various ways, depending what was the issue at hand:
# Mazda was ingenious to get the 2-rotor rated as a 1.3l (chamber volume 650cc) for tax- reasons
# Someone else made it a 2.6l for thermodynamics
# Some make it a 3.9l for swept volume of all chambers
How would you define it?
A 2l 4-stroke piston will pump 2l on one revolution, but only pump 1l
through the engine.
A 2l 2-stroke engine pumps 2l through everytime.
There is always arguments, depending on the viewpoint.
You are right the Rotary will never be a true diesel (Self-Ignition/Compression-Ignition), but the idea behind a Kerosene/Diesel/Jet-A burning Rotary in Aviation is not increased efficiency, but fuel availability.
As it is always going to be spark ignited the K-Rotary doesn't have to be as sturdy as a true diesel. Those torque-spikes from a diesel do need a sturdy (speak heavy) block!!
2-stroke oil in rotaries:
I really don't know where you picked that up!
It is true that some people that converted Mazda Rotaries for aircraft use do mix the fuel with 2-stroke oil, but this is not the rule. These individuals just feel it's easier than to mess with the original injection-pump, which takes the oil from the engine sump.
Others use a separate oiltank and the stock or aftermarket oil-injection pump.
Others leave the stock system alone, save for exchanging the crappy stock plastic lines for something better.
These plastic lines cause all the bad reputation, when they crack from old age and heat and start to leak, leaving the seals without oil. However you need a really old junker to find that.
If I ever get to build my own motor, i keep the stock system with a possible aftermarket pump, good lines and most important: good oil in the pan.
Synthetics are the rage.
The oil consumption is a fraction what a Lycoming throws out the breather on a good day!!
I doubt you would have to ever top off a well built Rotary between oil-changes.....
On one of the forums I just read about the imminent first flight of a Lancair ES with a Turbo-3-Rotor that was dynoed at 500hp - chamber volume is still 650cc.
So even if you are very conservative, a 4-rotor can easily hit the 600hp range and wouldn't even push it.
200hp from a 2-rotor without turbo is a good average....
Careful assembly and systems integration is of course mandatory - but there are good, sad and horrible samples with pistons just as many.
You mentioned pumping efficiency.
Once the Rotary is correctly tuned it will easily run at volumetric efficiencies higher than 1, and that without a turbo.
Of course that means you will have to run it at a specific rpm setting, but in Aviation in general and helicopters specifically this should not be a problem.
This only concerns pumping efficiency however - how the aerodynamics considering combustion work is a different game - one of the downsides of the Rotary.
If you are specifically interested in Rotaries for Aircraft, I really recommend you join the newsletters mentioned in a previous post.
As a primer go to
http://www.rotaryeng.net/ and start reading all the tech-papers about THE ENGINE!
For installation details scroll to the technical topics.
Warning: There is other ways to do things, what is posted is only one way, though well worked out!
For certified engines, you want to follow Mistral's progress closely!
http://www.mistral-engines.com/
Cheers,
3top,
