gmcjetpilot
Well Known Member
Great post as usual
For peak power @ 2250 RPM, ROP BSFC is 0.556 at 200hp or 18.5 gal/hr. 0.556 BSFC is great at peak power, actually better than a Lyc at peak power? I'd have to see it in a plane flying.
For ECON power @ 2100 RPM, LOP BSFC is 0.444 at 168 HP. WOW! A Lyc can run nominally at .42 econ but at 75% power. At 65% a Lyc can get 0.38 BSFC. Taking normal econ of .42 v .444, that is 5.7% worse for the rotor, which is better than the 10% difference I'd expect. But the Wankel G-200 is at 84% power! WOW! We shall see.
Second, they show at 2100 RPM (assume @ prop) for best LOP BSFC. At that RPM, from ROP to LOP, you get 16.8% better BSFC for 11.8% less HP! The .444 BSFC @ 168 HP is 12.5 gal/hr. That is crazy great. I would just have to see that in real world tests.
From the .556 (peak power @ 2250 rpm) to .444 BSFC (LOP @ 2100 rpm), gives 25.2%!!!!!!!!! That is incredible. I'd just have to see it. I hate to be suspect; these numbers are extremely fantastic! I wounder if the low RPM is an issue in the way Wankel pilots fly? It sounds like you need a prop designed to be efficient at 2100 RPM or 2250 RPM max? I see what Tracy was saying at RWS, about the Van's fly off, that RPM was too high for the Wankel. The Lyc can run low RPM's as well, which also helps a Lyc and it's prop efficiency wise.
Piston engines can run LOP very nicely but no where near 16.8% improvement from peak power to LOP at one RPM. LOP might give you 4% better BSFC in the Lyc. Fantastic numbers and hope they turn out to be true in real world flight.
You can see your overall block fuel econ can be shot, if you don't run ROP too much. Not leaning on either engine, Lyc or 13B, will cost you at the pump. The claim to fame I hear is the Wankel can run LOP all the time? OK.
The data is nice because it does show the difference in HP as I have said. People look at just less fuel burn but there is a cost in HP and of course speed. A Lyc can be dialed back to low power (65% or less) and leaned to just short or roughness or LOP for great econ.
HP for HP, LOP or not, I still think piston engine for all its oldness has some awesome properties. That is all I am saying. Clearly some fly offs are needed. Dan C's econ air race on April 5th was pretty good. Dave L's turbo wankel RV-6 made a nice show of it, but it was 7th out of 9 in fuel econ. Good yes but not better. The top half or 4 econ finishers (all Lycs) had an average GPM of 17.6 mpg. The rotary was 13.3 mpg. That is 32% difference! Somewhere there is a disconnect from data to real world and Mistral wants us to believe they have solved Wankel fuel inefficiencies. I hope my suspicion is belayed and I am wrong.
Again the caveat is racing is not real world flying but its good data, since most RV's fly their planes more aggressively then in econ mode.
Here is the basic numbers for the Lyc no magic LOP. If you believe the numbers above (which the took off their web site?) than the Wankel is better than a Lyc in every way. I don't believe their numbers, but I stand to be corrected. If they ever get any out to the market (cert or amateur) we shall see. If I was buying a new Mistral from my Piper I would get a lawyer to put it in writing for a guaranteed fuel burn.
Bill I love your post and respect your opinion. Great info. That is cool info. I would make a few comments. The first being these numbers are unbelievably good, two or three rotor. Not that I don't believe them, just that they are fantastic numbers. I'd need to see it in a plane. Where did you get this. Is it on their web site?http://img382.imageshack.us/img382/4978/powerandfuelconsumptionen7.jpg
http://img241.imageshack.us/img241/9444/powerandtorquefo7.jpg
The reason for the comments about LOP operation is that the rotary has proven to run well LOP to an extent that piston engines won't even run there. certification testing for the G300. (300 HP 3 rotor). I find it interesting that three rotors is only 200HP. So if two rotors is that 133 hp?
Bill Jepson
For peak power @ 2250 RPM, ROP BSFC is 0.556 at 200hp or 18.5 gal/hr. 0.556 BSFC is great at peak power, actually better than a Lyc at peak power? I'd have to see it in a plane flying.
For ECON power @ 2100 RPM, LOP BSFC is 0.444 at 168 HP. WOW! A Lyc can run nominally at .42 econ but at 75% power. At 65% a Lyc can get 0.38 BSFC. Taking normal econ of .42 v .444, that is 5.7% worse for the rotor, which is better than the 10% difference I'd expect. But the Wankel G-200 is at 84% power! WOW! We shall see.
Second, they show at 2100 RPM (assume @ prop) for best LOP BSFC. At that RPM, from ROP to LOP, you get 16.8% better BSFC for 11.8% less HP! The .444 BSFC @ 168 HP is 12.5 gal/hr. That is crazy great. I would just have to see that in real world tests.
From the .556 (peak power @ 2250 rpm) to .444 BSFC (LOP @ 2100 rpm), gives 25.2%!!!!!!!!! That is incredible. I'd just have to see it. I hate to be suspect; these numbers are extremely fantastic! I wounder if the low RPM is an issue in the way Wankel pilots fly? It sounds like you need a prop designed to be efficient at 2100 RPM or 2250 RPM max? I see what Tracy was saying at RWS, about the Van's fly off, that RPM was too high for the Wankel. The Lyc can run low RPM's as well, which also helps a Lyc and it's prop efficiency wise.
Piston engines can run LOP very nicely but no where near 16.8% improvement from peak power to LOP at one RPM. LOP might give you 4% better BSFC in the Lyc. Fantastic numbers and hope they turn out to be true in real world flight.
You can see your overall block fuel econ can be shot, if you don't run ROP too much. Not leaning on either engine, Lyc or 13B, will cost you at the pump. The claim to fame I hear is the Wankel can run LOP all the time? OK.
The data is nice because it does show the difference in HP as I have said. People look at just less fuel burn but there is a cost in HP and of course speed. A Lyc can be dialed back to low power (65% or less) and leaned to just short or roughness or LOP for great econ.
HP for HP, LOP or not, I still think piston engine for all its oldness has some awesome properties. That is all I am saying. Clearly some fly offs are needed. Dan C's econ air race on April 5th was pretty good. Dave L's turbo wankel RV-6 made a nice show of it, but it was 7th out of 9 in fuel econ. Good yes but not better. The top half or 4 econ finishers (all Lycs) had an average GPM of 17.6 mpg. The rotary was 13.3 mpg. That is 32% difference! Somewhere there is a disconnect from data to real world and Mistral wants us to believe they have solved Wankel fuel inefficiencies. I hope my suspicion is belayed and I am wrong.
Again the caveat is racing is not real world flying but its good data, since most RV's fly their planes more aggressively then in econ mode.
Here is the basic numbers for the Lyc no magic LOP. If you believe the numbers above (which the took off their web site?) than the Wankel is better than a Lyc in every way. I don't believe their numbers, but I stand to be corrected. If they ever get any out to the market (cert or amateur) we shall see. If I was buying a new Mistral from my Piper I would get a lawyer to put it in writing for a guaranteed fuel burn.
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