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Lycoming or Alternative Which is MORE reliable?

Great post as usual

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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
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?

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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Another REAL choice

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?

These charts come direct from Francois the CEO of Mistral. He posted these charts in an e-mail to the aircraft rotary engine newsletter. Yes these numbers are great, and like you I want to see them verified in an independent test before I accept them as gospel. The Charts are for the G200 2 rotor. Francois says that the 3 rotor scales directly with just 50% more of everything. 300 HP in the 3 rotor, and corresponding increases in fuel burn. The 3 rotor actually compares a bit better power to weight wise, which is why I susppect they decided to certify it first. Since it will be up against Lyc 540's and other big sixes.

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.

<snip> for acceptable length sorry.

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.

Correct, that is prop rpm. Their reduction is 2.82:1 so that corresponds to 5922 engine RPM. If you remember some of my other posts George I mentioned that the rotary has a "sweet spot" at 6000 RPM there the engine has been shown to make nearly zero bearing load, in instrumented tests. The balance, compression, and exhaust work best there. It makes sense that if you waste the least HP to friction that the BSFC should be best there, so that makes sense. High RPMS are no sweat for the rotary either so everybody is spinning the engine up. Using 7000 as a redline won't make much stress at all.

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.

George, you aren't wrong at all. If you asked Dave Leonard if he had the most fuel efficient wankel running He would laugh and say NO WAY! Dave re scooped his cowl and put a none to clean chin scoop on it. It cools great, but Dave would admit it isn't even close to optomised for drag. Daves is a fine home garage engine job. He did eveything himself except re-trimming the turbo to make LESS boost. He does have Tracys EMS which does allow him to lean the engine. This ability to run lean seems to take advantage of the charge being forced infront of the plugs in sort of self stratification. Tracy says his was still running smooth at 18:1 air/fuel ratio on a wide band sensor. This was something truly unexpected. Mistral said it seems to corresopond to the "tuned" areas. This is an area that Mazda really hasn't put much work in because they are trying to get the engine to produce better HP and efficiency at LOW rpms for better mileage in a car. For aircraft we almost never see less than 50%. In a car the operational percentages are reversed. A street car rarely sees greater than 50% and then for only a few seconds.

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.

George, I don't believe the wankel will be better in every way. I am skeptical of presented figures as you are. There are several areas in which the rotary WILL shine and one of those will be reliability once the ancilliaries are properly worked out. The other is power to weight which everyone expected anyway. The reason I believe Mistral has the best chance of any non-conventional engine company is because most of their Board of Directors are pilots, and they truly understand what is needed in an aircraft engine. Their work is truly professional, meticulous, and at the same time they are excited about the product. Francois said that they kept a bottle of champaign cold for the day the tuning of the 2 rotor started breaking 200HP without excessive RPMs. They have a VERY advanced EMS which helps to get those numbers up. Their castings for the intake are simply a work of art. When you look at one of the engine/PSRU combos sitting on the bench your mind says AIRPLANE ENGINE. I think these guys would do well if asked to optomize a conventional engine as well. Their purpose built gearbox is a solid design, using straight-cut gears made for this planetary. They are using a fairly high reduction 2.82:1 so they have a low prop RPM to get good efficiency. Again this shows their engineers know how to get more out of the combination. My rooting for Mistral is pretty greedy on my part. First I will probably use one of their PSRUs if I possibly afford it. Second, if and when they succeed in certifing the rotary, I'll be able to show my insurance company that my engie isn't unique and hopefully get lower insurance rates! My contention all along hasn't been that the rotary is better, rather that it is just as good in most areas and allows us another genuine choice for our aircraft.
Bill Jepson
 
I am excited

I hear you Mr. Bill Jepson. The numbers are not fantastical unbelievable just really really really really good. If they can produce that in an airplane I will be very happy. I still think they face a issues with market, installation, cost and Lyc and TCM inertia. New small GA planes are pretty slim to nill. It really needs to be in a new plane installation. The idea of retro fitting an engine that cost $??,??? :eek: plus prop and installation will be hard. It's not like the Lycoming or Continent are terrible and parts hard or expensive to get.

I have to admit a three rotor Wankel is pretty sexy. The Mistral with their smooth flowing induction, serious looking not home-brew looking PSRU and pro Mil Spec installation and wiring is fancy snazzy.

As an incurable selective cheap skate, it has to be better and cheaper to turn me on. Not better but more money, not so much a turn on. A lot better and more money, than yea sure. They have not crossed the A LOT better to cost threshold for me. If I had lots of money I would consider a three rotor job, if they made it available to us RV folks. It would make a nice RV-10 engine, a tad too much for two seat RV's.

You go back to 2004 they had delivery dates, prices and performance on the web site. To be fair bringing a new engine to market, is really hard. The road to engine certification is littered with lots of engine projects. It does not mean they where bad, just all the challenges I listed are expensive and time consuming. In the end price matters. If they can't sell an engine with as good performance or better for less or same money, it's going to be hard. Since retrofit means major mods to systems, engine mount, cowl to name a few, it will be a hard sale. Lycs and TCM are in production and fairly cheap, especially Lycs due to competition from Lyc, ECI, Supr.

If Mistral goes for the experimental market, that would be great! The problem is people can buy used 13b from a junk yard (buy two or three they are cheap) and overhaul them. Than buy a bunch of RWS stuff (ECU, PSRU, Mount....etc) and have an engine for less than $16k with out much guess work. The Mistral three rotor engine is in a different class. I would try and find a three rotor Mazda (rare right) and home brew it from the get go. A PSRU might be an issue? The two rotor 13b's are too small for a RV-10 IMHO. It will fly, just not with RV IO-540 performance. From Dan C's Econ 111 mile Air race, showed Dave L's RV6 rotor pwr'ed bird could fly with the big boys. So I hate to suck enthusiasm out of the sails of rotor enthusiast. I just want people to be realistic and know all sides before committing. The more informed and experienced know all the pros and cons.

A newbie might believe some of the hyperbole that Lycs are dangerous and Wankel's are perfect and superior in every way.
 
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Wow George we have agreement!

<snip>
I have to admit a three rotor Wankel is pretty sexy. The Mistral with their smooth flowing induction, serious looking not home-brew looking PSRU and pro Mil Spec installation and wiring is fancy snazzy.

As an incurable selective cheap skate, it has to be better and cheaper to turn me on. Not better but more money, not so much a turn on. A lot better and more money, than yea sure. They have not crossed the A LOT better to cost threshold for me. If I had lots of money I would consider a three rotor job, if they made it available to us RV folks. It would make a nice RV-10 engine, a tad too much for two seat RV's.
Hey George, guess what I have in my shop? Answer: A 3 rotor 20B and an RV-10 kit!

<snip>

If Mistral goes for the experimental market, that would be great! The problem is people can buy used 13b from a junk yard (buy two or three they are cheap) and overhaul them. Than buy a bunch of RWS stuff (ECU, PSRU, Mount....etc) and have an engine for less than $16k with out much guess work. The Mistral three rotor engine is in a different class. I would try and find a three rotor Mazda (rare right) and home brew it from the get go. A PSRU might be an issue? The two rotor 13b's are too small for a RV-10 IMHO. It will fly, just not with RV IO-540 performance. From Dan C's Econ 111 mile Air race, showed Dave L's RV6 rotor pwr'ed bird could fly with the big boys. So I hate to suck enthusiasm out of the sails of rotor enthusiast. I just want people to be realistic and know all sides before committing. The more informed and experienced know all the pros and cons.

A newbie might believe some of the hyperbole that Lycs are dangerous and Wankel's are perfect and superior in every way.

I think you are hitting the market nail exactly on the head George. I have long believed that the way to get acceptance of a new certified engine is to first sell to the experimental builders. After you gain acceptance and prove good performance figures regular aircraft companies will take you seriously.
I personally strive to keep the hyperbole to a minium. I have NEVER felt that Lycs and other certified engines are dangerous, quite the opposite, I feel that they have earned their placement in the market through long service. My focus is to educate some of our other people that a rotary engine, when properly engineered and installed ISN'T dangerous. My knowledge shows me that many engine types CAN work. We must approach the design work with our eyes open. I am always aware that my engine package will be an example, good or bad, for the use of alternate engines as a power source.

Bill Jepson
 
The whole world is watching....

Bill;
I agree with your last sentence about being an example that others will notice, particularly if something goes wrong.
I'm sensitive to the issue, as a builder of an RV8 with an 'alternative' engine, I hear comments. I observe reactions to aircraft taking off with 'alternative' engines, usually negative comments about the sound and then ad hominum insults etc.
If our planes fly fine we don't get alot of credit, but if we have any kind of failure, the 'alternative' engine will promptly get mentioned.
I do a lot of 'double-triple idiot checks' and have other open minded poeple look at my 'plant' for possible failure modes and poor engineering.
Mainly I get a lot of blank looks and glassy stares.
 
Bill;
I agree with your last sentence about being an example that others will notice, particularly if something goes wrong.
I'm sensitive to the issue, as a builder of an RV8 with an 'alternative' engine, I hear comments. I observe reactions to aircraft taking off with 'alternative' engines, usually negative comments about the sound and then ad hominum insults etc.
If our planes fly fine we don't get alot of credit, but if we have any kind of failure, the 'alternative' engine will promptly get mentioned.
I do a lot of 'double-triple idiot checks' and have other open minded poeple look at my 'plant' for possible failure modes and poor engineering.
Mainly I get a lot of blank looks and glassy stares.

Quite true. I have had a number of ATC guys in the tower state how great my Subaru sounds however so there are a few open minded people out there. Show some traditional engine guys my engine and the blank stares and dumb questions fly- so it that the turbo? Ahhh, nope that's the air filter...:(

There are plenty of Lycoming powered RVs performing uncommanded descents to terra firma every year but when an auto engined one comes down- we get all the headlines. Gee thanks. Power loss accidents are never fun no matter which engine you fly. It's a good thing to learn what caused them alright but always best to wait for the official word before starting the finger pointing.
 
It is a big deal

Quite true. I have had a number of ATC guys in the tower state how great my Subaru sounds however so there are a few open minded people out there. Show some traditional engine guys my engine and the blank stares and dumb questions fly- so it that the turbo? Ahhh, nope that's the air filter...:(

There are plenty of Lycoming powered RVs performing uncommanded descents to terra firma every year but when an auto engined one comes down- we get all the headlines. Gee thanks. Power loss accidents are never fun no matter which engine you fly. It's a good thing to learn what caused them alright but always best to wait for the official word before starting the finger pointing.
Ross I don't have an opinion about fly-by engine sounds of an alternative engines. I guess its personal preference, but if someone doesn't care for it, than they're not open minded? :D


There are plenty of Lycoming powered RVs performing uncommanded descents to terra firma every year but when an auto engined one comes down- we get all the headlines. Gee thanks.


I don't follow the logic or sentiment. What happens to an engine and installation that has only a handful examples (or one or few 100 equivalent installations) flying, an incident or accident is a big deal. I would think you would want to know the reason why. Is it not part of the alternative engine joy, the fact they are rare, cool, different, custom? That also means alternative engines are often untested or involve new (custom) applications/installations. There is some risk that goes with that, if we are all being honest.

I disagree with your comment that there are plenty RV's with Lycs losing power every year. Do you have any facts? The NTSB data does not support that at all.

To be blunt, if I limit my search to Lycs in experimentals there are almost NO Experimental's that have lost power due to mechanical failure. Compared to all alternative engines, Lycs are superior statistically in experimentals, when it comes to loss of power. If you look at loss of power due to ancillary systems the Lyc is clearly superior statistically with its old fashion mechanical fuel and ignition systems.

The high time Alt engine & gear is my only be 500 hours. The highest time engines are in the 1000 hour or may 1,500 flight hour range. Lycs have millions and millions of flight hours as a fleet (every few years!). When it comes to standard, nothing is as standard as a Lyc and its installation. That's a big advantage. That's not a put down of Alt engines, which stands on their own ground and relative fleet size.

To mention Lyc in the same breath with Alternative engines as some reason or justification for alternative engine failures is faulty logic. It's not relevant to the safety of any alternative engine. Alternative engines need to stand on their own, not look to the Lyc. I understand the Lyc is the gold standard and a bench mark to aim for.

There's NO feeling good about any accident, alternative engine or not. Its just irrelevant to play the blame game on Lycs. So if a Lyc fails does that make it better for alternative engines? I just don't get it. Personally I don't point at any accident for a "Gotcha!". I look at it to learn.

The Egg engine and unique prop in a RV-10 airframe, a rare combo, was involved in a tragic accident. There aren't may of these six bangers flying much less in that airframe, so YES IT TAKES ON MORE IMPORTANCE IF A RARE BIRD GOES DOWN.

I guarantee if the first of new kind of Lycoming or Continental to come out in decades, had an engine related accident, it would make the news.

The new certified / prototype diesels that quit due to a battery issue in that "Diamond twin" made news. It's new and fairly untested so its big news. Let say in 20 years from now there are 20,000 diesel Diamond twins flying, it will not be big news if one falls out of the sky.

Alternative engine guys need to stop bashing Lycs to support a decision to fly what ever you want. Vice verse, the petty bashing of alternative engines is silly stuff you all should ignore as well. Personally I like the sound of a P&W radial the best. The main charter we all have is to make flying as safe as possible regardless of the engine we fly behind.
 
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George,

That is probably one of the most well reasoned posts I've seen regarding the whole "engine debate". I just stay out of it because I think people on both sides just get crazy stupid. People throwing data all over the place out of context and entirely useless (on both sides), so on and so forth.

I chuckle when I see people using "data" to support their decision either way. Pick your poison, stick with it and don't worry about trying to convince others. Do what is best for YOU - period. I fly behind a Lyco because it's best for ME, but not for everyone. Some people even choose to fly behind turbines, diesels, wankels, franklins, subies, etc.. They are still people, they are still homebuilders, they are still customers, pilots and some are even friends of mine. That doesn't make them bad people or me a bad person for not going alternative. It means we each chose something different. It means I don't have the patience, skill or courage that Ross does to research, design, develop and ultimately test my own setup. I'm barely a capable pilot with the stuff I fly behind now, much less trying to be a test pilot!

I always want to know what caused any crash, no matter what the engine because I have lost good friends who were flying behind both Certified type and Alternative engines. I do have to agree overall that regardless of the Lyco / Subie / Wankle sounds....nothing beats a nice round engine!

Anyway, good post.

Cheers,
Stein.

PS - Ross....I haven't seen that crazyweird congolmeration of Tempest /Napier /DC4 /Bristol "data" post again for a couple days now, aren't we due another post of it?!?!? All in fun, I promise! :)
 
Sounds and Choices

Stein,

You always post something well reasoned and usually amusing.

People sometimes do get upset about the smallest things. I was merely posting that there are SOME traditional engined guys who will admit that my Subie sounds ok, if different. Most seem genuinely interested- or perhaps amazed that it does work. Other pilots seem to have the view that the idea of a car engine in an aircraft is nuts or scary, much like the view some certified aircraft pilots have of our RVs. So I used the phrase "open minded" to describe those who don't fly auto conversions but can appreciate them.

When it comes to sounds, well that is subjective like looks for sure. An R-3350 pumped up to 80 inches rounding the pylons at Reno sounds good but doesn't make the hair stand up on the back of your neck like Strega's Merlin at 125+ inches and 3400 rpm- the nicest sounding engine in the world- IMO.

I can't say I'm fond of the sound a 4 banger Lycoming RV makes with twin pipes- kinda coarse but I do fancy the sounds of twin TIGO-541s in synch on a PA31P (fond memories) or the race Continental and Lycoming sixes in the Sport Class. That's good music!:)

My hangar neighbor next to me owned a beautifully clean Citabria for many years powered by an O-360 "fish boat motor" (his words). He is importing an RV7 to replace it next month from Texas as he has had RV envy really bad after watching me taxi by all the time and having a flight in the 6A. The RV7 will share his space with a Buick V8 powered, one off replica Spitfire which looks extremely authentic and sounds very close to the part too. I consider Tim open minded with his choice of aircraft and power plants. You certainly wouldn't have an O-360 in a Spitfire replica!:eek:

I can't wait to do some more formation work and shoot some pix and video when Tim gets the -7 up here. I'm glad that Tim has a "fish boat motor" powered RV so I have someone to play with- even if I won't be able to keep up with him.:(

It's the flying experience that counts for most of us, not what turns the fan up front. I know Tim is really going to enjoy his RV- not sure how much he'll fly the Spit now!
 
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