Mazda Rotary - what are the issues to be overcome?

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RSD

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I'm fortunate that I've got access to one of the best Mazda Rotary engine builders on the planet, and we have been discussing the development of an engine package specifically built for homebuilt aircraft. But it seems like there is a lot of jungle drums and whispers stuff out there about exactly what are the issues that need to be overcome, and to make any project a success you first have to define the problem(s)

So I would welcome information from everyone on what exactly the issues are that need to be overcome -
  • cooling apparently is one of them
What else?

What we have defined so far as specs are
  • all alloy 3 rotor engine for lower weight and better cooling
  • engine will have one (possibly two) turbos
  • engine output will be 300 shp so that they work with the AutoPSRU 200Za
  • redundant ECU's
  • engine will be capable of being used in aerobatic aircraft
Any and all thoughts are welcome and appreciated
 

Vigilant1

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The PSRU has proven to be the biggest challenge for previous efforts to fit a prop to a Wankel engine. It has been done successfully (by PowerSport, and by others), but it has not been easy. The torsional vibration and torque pulses of the Wankel are certainly not an insurmountable issue, but PSRUs suitable for use in 4-6 cylinder engines have often not been suitable for use in Wankel engines of similar power.
 

AdrianS

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The PSRU has proven to be the biggest challenge for previous efforts to fit a prop to a Wankel engine. It has been done successfully (by PowerSport, and by others), but it has not been easy. The torsional vibration and torque pulses of the Wankel are certainly not an insurmountable issue, but PSRUs suitable for use in 4-6 cylinder engines have often not been suitable for use in Wankel engines of similar power.
The OP mentions a three-rotor engine, so presumably more but smaller pulses per rev than a twin rotor.
 

RSD

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We believe that the three rotor will be suitable when it comes to overcoming torsional vibration and torque pulses, a four rotor is better still.

Is Powersports still in business? Their website isn't.

AutoPSRU rate their 200Za unit as suitable for 300 shp from a Mazda Rotary so it sounds like they have tested it sufficiently to say that it is good for that - but we are open to other options if there is better out there.
 

RSD

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BTW if anyone has anything else that they would like to see included in a rotary engine package for aviation please let me know.
 

Vigilant1

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AutoPSRU rate their 200Za unit as suitable for 300 shp from a Mazda Rotary so it sounds like they have tested it sufficiently to say that it is good for that ....
That assessment requires hundreds of hours of realistic testing, then flight testing. That happens after some fairly involved analysis and calculation to rule out the obvious problems. You should ask to see their testing reports if they are claiming that they know their drive will work in your application. Don't wish this away or you'll be sorry.
 

rv6ejguy

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Agree. If a drive manufacturer hasn't run your engine type with a prop on a test stand or flown it in an airplane, they don't know if it will be reliable and free from TV issues, period. Further, the tests should be done with a prop having close to the same MMOI as the prop you'll run and recommend to customers.

I'd also look at the potential market size for 300hp class engines. The market is much bigger for 200hp class ones.
 

RSD

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I've only just got email functionality back again after a big upset at my ISP so I will ask them.

The 300hp model is needed for a new kit plane that I'm involved in developing, but we can certainly look at a 200hp model as well - it might even be possible to make a 200hp model that is direct drive.
 

rv6ejguy

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That's fine if you're developing for a specific market and probably best to confine the engine to one hp target. Designing and building an airframe plus doing an engine development project at the same time is a HUGE task. No point in diluting your time with a second engine project.
 

RSD

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Agreed - we will get our project sorted first then do other horsepower engines
 

rv6ejguy

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Get the engine built and on a dyno for testing soon and get one on a test stand with PSRU and prop soon after while you work on the airframe. You'll have some decent experience and time on the powerplant package by the time the airframe is designed and built. This will help give you and customers more confidence in the FWF stuff.

Since this is a clean sheet design, design it around the engine and liquid cooling from the start with a properly integrated, low drag radiator and oil cooling system. The turbo Wankel will have high oil cooling requirements as others have discovered.

Wish you good luck in this project.
 
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BJC

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BTW if anyone has anything else that they would like to see included in a rotary engine package for aviation please let me know.
I’ve only seen and heard a couple of rotary powered homebuilts. They performed well for the brief times that I saw them in flight, but they badly needed a muffler / exhaust system to eliminate the very irritating noise that they made. I realize that some may deem that to be insignificant, but I would not buy a kit or airplane that made such an irritating sound except as a dedicated race plane or unlimited aerobatic competition plane.

BJC
 

Vigilant1

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I’ve only seen and heard a couple of rotary powered homebuilts. They performed well for the brief times that I saw them in flight, but they badly needed a muffler / exhaust system to eliminate the very irritating noise that they made. I realize that some may deem that to be insignificant, but I would not buy a kit or airplane that made such an irritating sound except as a dedicated race plane or unlimited aerobatic competition plane.

BJC
That's very true of a normally aspirated Wankel:. The exhaust pulse is so energetic and has such a rapid rise time (no valve in the way) that they need a muffler. And not just any muffler, due to the heat. But the turbo does a lot to tame the exhaust note.

Conventional wisdom discourages, for good reason, the fitting of a newly designed powerplant to a newly designed airplane. Both undertakings are big tasks, but together the work and developmental risk is more than the sum of the two efforts--it is closer to being their product.
 
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RSD

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Conventional wisdom discourages, for good reason, the fitting of a newly designed powerplant to a newly designed airplane. Both undertakings are big tasks, but together the work and developmental risk is more than the sum of the two efforts--it is closer to being their product.
Agree totally - but a necessary evil in this case unfortunately as one of our design requirements for the plane is a FADEC or similar engine, and unfortunately something like a Lycoming IE2 is $120,000 which doesn't suit the project. One slight advantage to this though is that it will allow us to design the Mazda's cooling/airflow needs in from the get go.
 

Vigilant1

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Agree totally - but a necessary evil in this case unfortunately as one of our design requirements for the plane is a FADEC or similar engine, .
Well, no problem at all, as long as whoever set that requirement knows the implications ( in cost and time) and will accommodate them ( in funds and scheduling).
 

apmartin00

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The 300hp model is needed for a new kit plane that I'm involved in developing, but we can certainly look at a 200hp model as well - it might even be possible to make a 200hp model that is direct drive.
Ok, I'm going to try and be tactful, But your comment shows you really need to do more homework or your just going to be giving away your kids inheritance. I don't want to curb enthusiasm but from your posts I feel your looking at the rotary for all the wrong reasons. have you even gone outside & done market research and talked to some rotary flyers? You don't have to start from scratch, Search for and purchase an existing RV with rotary, get some experience with it before putting in your own firewall forward package and testing that for at least 1000hrs before even considering selling another half arsed package that just ends up giving alternative engines a bad name.
I built & fly behind a 13b Renesis & have a 20b ready for next plane. So I have a little experience in these, I love the rotary, and reckon it is a great aircraft engine and better than ever it was as a car engine. I built mine because I could, not because I ever thought it would be better or cheaper.
Everytime I hear someone say they want to use automotive engines because they cant afford a similar power Lycoming, I laugh, just shows naivety towards their project. basically power costs money. these also cost time. end result is similar or more, very rarely less.
As to your quote above, The only way you can direct drive a rotary is to have a ducted fan, that's been done, but not persisted with.
Andrew
 
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