Wankel rotary engine

[kyleb]

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If you have the money and want to get flying quickly I recommend you buy a FWF air cooled 4 banger installation, strap it up and go flight test and get it on.

If you want to try something different and have the patience and aptitude for it, I'd advocate the rotary over other auto conversions.

Dave, you make a lot of good points, but what is the real service history on Rotaries? IMO, that's where the theory and reality diverge. As far as I know, there really aren't any rotary fliers who have demonstrated the engine/PSRU/Induction/Ignition system to be a practical powerplant for aviation use.

Tracy Cook has a thousand plus hours on his airplane, but that represents several rebuilds, upgrades, etc. I'm not aware of anyone who has a rotary installation that was installed, debugged, and ran 500-1,000 trouble free hours. Who out there has done that? Any estimates of the total fleet hours on rotaries?

 

[Ted]

Dave, do you have dyno data showing a BSFC of 0.47 out of a rotary on boost at the powers you'd need for an aircraft? I'd like to see them if so, because I've never understood rotary engines to be efficient at all.

Depending on which Lycosaur/Contisaur you run, you'll typically be in the low 0.4s. The 300+ hp turbocharged variants may have trouble with this, but naturally aspirated (300 hp or less) it's simple.

There are a lot of different ways you can power your airplane. If I was going to build an experimental, I'd go with an automotive engine that I built up myself (which one would depend on the aircraft). However that's because I'm cheap, an engine guy, and wouldn't be able to buy a suitable Lycosaur or Contisaur that makes the power I want for less than $50k... and I'd want two of them.

 

[Henning]

Dave, do you have dyno data showing a BSFC of 0.47 out of a rotary on boost at the powers you'd need for an aircraft? I'd like to see them if so, because I've never understood rotary engines to be efficient at all.

Depending on which Lycosaur/Contisaur you run, you'll typically be in the low 0.4s. The 300+ hp turbocharged variants may have trouble with this, but naturally aspirated (300 hp or less) it's simple.

There are a lot of different ways you can power your airplane. If I was going to build an experimental, I'd go with an automotive engine that I built up myself (which one would depend on the aircraft). However that's because I'm cheap, an engine guy, and wouldn't be able to buy a suitable Lycosaur or Contisaur that makes the power I want for less than $50k... and I'd want two of them.

Over the years I've had a couple dozen Wankels on the dyno, all racing units, 2,3 & 4 rotor even a couple I've done, I've never seen better than .53, more typically .55-.57. Not saying it isn't possible, but I've never seen it done. I haven't done anything with them since RX-7 days so maybe with the upgrades in technology they're doing it now. I was going to try modifying the rotor some, but I didn't have access to the machines to make it practical. I though maybe if the cases were made of ceramic the efficiency could be improved, but I wasn't smart enough and don't know enough about ceramics to figure out how to keep them from wearing or from cracking if using a metal liner.

The one thing I always wanted to do was build a 6 rotor to run Top Fuel since the engines drawbacks don't really matter in that application and I think the design lends itself to extracting the most work from the fuel.

 

[Doggtyred]

Dave, do you have dyno data showing a BSFC of 0.47 out of a rotary on boost at the powers you'd need for an aircraft? I'd like to see them if so, because I've never understood rotary engines to be efficient at all.

the .47 is not for boost. 0.55 is more typical of boosted engines, as Henning has pointed out.

But most of us flying smaller experimental airframes should do just fine with 160-180 hp normally aspirated.

I dont personally have copies of the dyno data. I've looked at various charts, reports and claims over the years of dealing with rotaries. I've googled a lot. I will also recognize that the rotary isn't the holy grail, nor is rolling your own a solution for everyone.

Like I said... I'm drinking the coolaid... I'm just not drunk on it :wink2:

 

[cessna182b]

Was that the Orenda V-8? IIRC that was a big block Chevy.

At the 2007 AOPA Expo at Palm Springs, there was a C-182 with a V-8. Of course there were promises of performance!

I recall an EAA member who put a small block Chevy V8 in a Grumman Yankee. He never flew it that I know of (though it appeared nearly finished). He moved away not long after I saw it, so don't know how it turned out.

Dave

 

[Richard]

nor is rolling your own a solution for everyone.

Like I said... I'm drinking the coolaid... I'm just not drunk on it :wink2:

But you have the vices covered. I bet you run with wild wimmin too.

 

[Henning]

the .47 is not for boost. 0.55 is more typical of boosted engines, as Henning has pointed out.

But most of us flying smaller experimental airframes should do just fine with 160-180 hp normally aspirated.

I dont personally have copies of the dyno data. I've looked at various charts, reports and claims over the years of dealing with rotaries. I've googled a lot. I will also recognize that the rotary isn't the holy grail, nor is rolling your own a solution for everyone.

Like I said... I'm drinking the coolaid... I'm just not drunk on it :wink2:

Thing is, at the 160-180hp levels the liquid cooled auto conversions arent really cost or weight effective, not to mention time effective as you will have minimum of multiple hundreds of hours involved getting it set up and working reliably. Auto conversions don't really become effective until you get into the 300+hp range, and even then it's only $$$ effective on rebuild as install and PSRU costs will make the initial costs still higher (the engine costs will be about the same when done building the auto engine and then add the PSRU), and never time effective.

Consider that the majority of experimentals get flown less than 100hrs a year, you're looking at 20+ years before you're rebuilding that O-320 or O-360 which on an experimental you do yourself (if you can rebuild one engine, you can do any) for $12k. Figure in the mean time you did another $8k of repairs to it and that's $1000 a year to have that engine. I've not seen an auto install that operates for less annual cost in repairs & mods while they operate at less than half the reliability, and that includes the 3 aircraft I have seen with Wankels (2 Cobra LSAs in Aus with 2 rotor naturally aspirated which were replaced with a Rotax 912 and 914 within a year due to reliability issues and a Lancair IVP that had a twin turbo 3 rotor that was replaced with a Lycoming 540 J2BD within a year).

If you want something to fly, put an aircraft engine on it. If you want something to tinker with, play with engineering and show off your craftsmanship and fabrication skills, then do an auto conversion.

 

[Ted]

Thing is, at the 160-180hp levels the liquid cooled auto conversions arent really cost or weight effective, not to mention time effective as you will have minimum of multiple hundreds of hours involved getting it set up and working reliably. Auto conversions don't really become effective until you get into the 300+hp range, and even then it's only $$$ effective on rebuild as install and PSRU costs will make the initial costs still higher (the engine costs will be about the same when done building the auto engine and then add the PSRU), and never time effective.

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If you want something to fly, put an aircraft engine on it. If you want something to tinker with, play with engineering and show off your craftsmanship and fabrication skills, then do an auto conversion.

I'd say this is an accurate assessment for most people. You can get the costs down, but you have to be an engine guy who's capable of doing the major work yourself, which most builders aren't. Plus think about how much effort goes into an engine development program for a manufacturer (answer: a lot) and think about whether you can really do just as well on the first try. Probably not, although there are ways to make it better or worse.

 

[Doggtyred]

If you want something to fly, put an aircraft engine on it. If you want something to tinker with, play with engineering and show off your craftsmanship and fabrication skills, then do an auto conversion.

I can agree with that statement right there...

And I can think of quite a few who're showing off their LACK of those skills and dragging out their projects for YEARS as a result.

 

[Herman vanOoijen]

There was an article a couple of months ago (not sure exactly which month, I'll check tomorrow) in the EAA magazine about Mazda Wankel's. It was really good (IMO) and focused on how you can make them work in certain airplanes. It also focused on the fact that while they do work for airplane engines, it takes a lot to keep them cool.

Someday, I'd like to build a BD-4 powered by a Mazda of some sort. Could make it work for sure with a 13B or 13B with a Turbo. Not sure exactly how much power a BD-4 can handle.

May be you should talk to Max Lasscher, who built a Falconar named "Wunderbird" with a Mazda Wankel [http://www.rotaryaviation.com/Success Stories.htm]. We see this plane several times during the year here at 6B4 [Utica, NY] when Max L. visits friends in the neighborhood. The plane is of exquisite workmanship and the sound of the Wankel , at first, made us wonder what was propelling the craft.