Eccentric

Too late to preach the Mazda gospel...I bought an EJ25 Subaru today...

Do as much testing as you can on the ground. Read the recent issue of Contact magazine to avoid the limp home mode that caused some grief to others.

Of course there are. Do Mazda rotary engined cars have engine failures less often than piston powered cars?

 

 

I can comment on this one, having owned 5 RX-7s. The 86 to 88 NA 2nd Gen RX-7s with the EFI 13B, same vintage that is in my plane, tend to fail the same way: after about 15 years the coolant o-rings get old and brittle and start leaking. Combustion pressure slowly blows the coolant past the pressure cap, overflowing the catch bottle. You will know this is happening when you see the coolant temp slowly rising. Tear down of these 150k to 250kmile engines show very little wear.

For aircraft use teflon o-rings are used instead of the Mazda rings.

 

I'm building with a 20B NA as my target power plant.

 

 

Good choice. I have a turbo 13B in a real engine mount bolted to a mockup LEZ firewall, a project that I started in 2001. I decided there is just no room in a LEZ for the turbo and the heat that it generates. Not to mention the potential reliability issues, and detonation will crack apex seals. A PPort NA 20B will be quite a performer.

When I started this thread I was really hoping someone with some subaru knowledge would chime in. I'm working on locating one ...EJ-25 looks to be a good bet..

It's not a turbine, though, as it still uses the Otto cycle, rather than the Brayton cycle. The inefficiencies have to do with the large sealing are, imperfect combustion chamber shape, and incomplete burning and concomitant high exhaust temperatures, rather than the cycle used.

 

We've had these conversations before, it's always fun to revive them once in awhile.

The rotary can be aggressively leaned (I don't practice that yet, but Tracy Crook does). I believe the BSFC will always be a marginally unfavorable compared to water-cooled reciprocatings but may not be significantly different than air-cooled reciprocatings.

Since this thread is under "Model Specific - Long-EZ", I forgot to mention my page with some fundamentals for installing a rotary in a Long-EZ.

http://www.bridgingworlds.com/LEZ13B/LEZ13B.htm

What is there to "get"? While in theory, lower parts count may reduce failure rates, the data does not support the notion that rotary engines have failure rates any lower than any other engines.

 

There's nothing to "get". If you like rotary engines, that's fine - they seem to work well in aircraft, if you don't mind having to search for mogas (especially out west) and having slightly higher fuel burns than aircraft engines, but the implication that you will have fewer failures due to the parts count (and moving parts count) is not born out by the epidemiological data.

 

Marc, as a mechanical engineer don't you find the Wankel engine, that tends more towards a turbine (hence higher fuel burn) than a "reciprocating" (in FAA speak), an elegant machine? [i had to list my engine as a "reciprocating" even though there are no parts in my engine that do that].

Me being of the electrical variety, prefer the simple moving mechanisms with electronic control.

You are right in that the parts count alone is not an indicator of overall reliability, as most actual failures of both rotaries and reciprocatings are rare and not usually in the engine itself. (Except for those rare crankshaft, rod and exhaust valve failures).

Before swapping it out for a Lycoming, as Joe Hull and Bulent Aliev are doing with their COZY's.

I don't know that Gowan ever got his Long-EZ flying again with any engine. Maybe he did. I thought he bought a Vari-EZ to fly while he was working on the Long-EZ. But that was a long time ago and I haven't heard anything lately....

Joe suffered from a broken spark plug - IMHO he was using the wrong spark plugs. Bulent got frustrated with the EFI.

I've had almost no issues, but I took the lowest risk approach with my install.

I've always addressed this in 10,000 words (or less.)

Amazingly some people still don't get it!

I think I've got the highest time in a rotary Long-EZ at 675 hours.

http://www.ductedfan.com

Before me there was Ron Gowan who put a couple hundred hours on a rotary LEZ in the mid 90s.

I put a couple 3D files up on the web. Use at your own risk. No guarantee of completeness or accuracy. I may not leave them there forever

http://www.bridgingworlds.com/3d_ez_engine.dwg

http://www.bridgingworlds.com/psru_prop_cowl_lg4.dwg

I reserved an N-number, now how do I determine how to find or get a serial number, registartion number et al. Its not complete yet, so do I have to wait for the FAA to certify it as experimental? How about the radio licence? Thanks to all that might help, may be finished in a few more months. I chose 227CF, the military guys will understand.

 

Oh yes, and how do I know what plan number I have, can't seem to find a number on the plans and Rutan guys don't answer emails...

You don't need a plans number. As builder, you can assign any serial number you want.

I'm interested in learning more about your mount & experience. We talked at Canards de Mayo in Columbia (I'm the guy that followed you down the runway asking questions about your rotary install) and I was intrigued by your implementation. You mentioned that you were essentially running an unmodified engine off mogas and that you hadn't done anything special to adapt your rotary to aviation use.

 

What performance are you seeing with this, and what do you guess (roughly) it would cost to duplicate?

Hi Ben,

I installed my rotary back in 1997, at the time I couldn't figure out how to put shock mounts in, so I didn't. The engine and mount are bolted directly to the airframe. You can probably only do that with a rotary! I've been refining the design of a new mount on paper for years now. I decided I'm not actually going to build and install the new mount until I have to take the engine off for some reason. That hasn't happened yet, over 5 years and almost 500 hours since the engine was last installed. There are other rotary projects in process on other airframes with this type of mount design.

You would want more power on a Cozy IV than I have (approx. 145 HP). This can be done various ways: porting, supercharger, turbocharger, 3-rotor, etc.

You can do it for under $10k including a professional engine build, PSRU and accessories.

http://www.bridgingworlds.com/LEZ13B/LEZ13B.htm

If there is enough interest in this engine mount design for the Long-EZ, I might have it produced for sale by a professional welder.

Perry

Check out this map, you will see that obtaining mogas at airports in

the West is almost impossible.

http://www.chouby.com/apps/autogas.html

When I've flown from Oregon to Kansas in the past to visit family,

I've had to enlist the help of EAA members/homebuilders enroute in

Montana and Utah to help me get mogas.

I decided to start the Mogas Assistance Network, so people can

volunteer to help us experimental/mogas-stc pilots get mogas when we

travel. Members would be aviation enthusiasts who would have an

interest in seeing homebuilt airplanes anyway.

Go to this link and add your name, location, email, and closest

airport if you want to help us out.

http://www.frappr.com/mogasassistancenetwork

Perry

http://www.ductedfan.com

It's essentially identical to the wing on the original Cozy and the Long EZ. The Cozy 4 wing is larger.

 

The differences between the Berkut wing and the Cozy wing are tiny. Bigger ailerons, a straight trailing edge (got rid of the kink at BL 55.5) and winglets tipped out just a touch - just for looks.

 

Mark's right. Bigger engine, smaller fuselage, retractable gear, slicker cowl, lighter empty weight. No magic.

Ronnenberg's Berkut was parked next to my Long-EZ at Columbia CA. In addition to no lower winglets, it appeared that the upper winglets were a few inches shorter as well (maybe 3"?).