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4 stroke engine..
Hey there all


The limited experience I've had with rotary engines has mainly been with ultralights and microlights but I think some of the learnings can be transposed to rotary wing aircraft.

Main problem we encountered in Australia was to do with cooling systems. With the microlight it wasn't too bad but in taxi the temps would creep up. Once in the air they were fine and as previously commented here they appeared to run well in regards to vibration in a variety of attitudes and flight envelopes.

In ultralights the temp was more of a noticeable problem with cooling systems requiring a booster fan while taxiing etc. Once airborne then the issue was not of significant concern.

As to fuel, using the Mazda engines we did not notice a significant reduction in fuel usage when compared to an equivalent 4 stroke. A point to be explored is the fuel system itself though. I've noticed in a couple of posts people dealing with vapour issues.

Would be interested in hearing more if the heat issue could be addressed and depending upon power output.

bryancobb - 10/28/2011 11:57 AM
Well .....The FAA wouldn't give him an airworthiness certificate, so it's a boat anchor.

This calls for some ULTRALIGHT MENTALITY!
Because its a helicopter application it would have to be a fan cooled radiator. So instead of the variation of cooling in an airplane during takeoff and cruise this engine will be force cooled at all times. Fan and rad will be sized to provide adequate cooling.
I'm with both Bryans on the 2-stroke issue. People flinch away when you say 2-stroke engine, because their lawn mowers break down!
But I had a lot of excellent 2-stroke Japanese motorbikes, and that was BEFORE CDI ignition and fuel injection.
I think it will be no problem to use this engine. It is almost all aluminium. It is smooth. If you had a radiator much like one on an air conditioner unit outside. Slide it over the engine and around the Main rotor shaft. Mount hard to the main rotor shaft, fan blades that spin opposit, then i think it would never have a cooling issue. I dont think you would anyways. Because it is not mounted inside of a tight cowling with IR heat reflecting back to it, it should not heat up more than it could handle.

Also, one book i have says that when comparing fuel numbers, the rotary is more fuel efficient. Also, it said that NASA says this engine can get more that a 3000 hour TBO. No one has been able to make that happen yet. With all of the new metal alloy's, we could build the three moving parts out of a very strong and very very light. With that, it could be spun at very high RPMs to generate large amounts of horse power per weight. They suggest that you could have a football sized motor producing well over 100 HP. But, no one has needed to do this just for cars.
The only thing holding me back to order a Mosquito is the 2 stroke engine. Hopefully a 4-stroke or Rotary engine option will be available soon.
MGL - great thing about experimental is you can modify to your hearts content -- buy now, modify later least you'll have fun while you wait
I personally do not feel comfortable with a 2 stroke engine, the inconvenience of mixing oil into the fuel, radio noise and other reasons. No point in building and then modifying. I have built airplanes, one with a 4-stroke Suzuki car engine conversion with custom SDS EM-4 EFI and ignition. I am an airline pilot and have been exposed to aviation (General, Commercial and Experimental) all my adult life. I had my share of engine failures, fires and forced landings (all on certified aircraft). So maybe my approach towards engine choice and risk assessment is more conservative. Just my personal preference.
Not implying that MGL is anything but a stellar/smart guy, but folks of average intelligence and mechanical ability can operate a 4-stroke powered helicopter, safely.
It HONESTLY takes a person with lots of experience with 2-strokes in Jet-Skis, Ultralights, Motorcycles, and/or R/C Aircraft, to fly a 2-Stroke powered helicopter, safely.
I would personally prefer a 4 stroke in a Mosquito, because well, that's what I was taught at school. The WyoTech Automotive Courses that I took, understandable, don't go much further than simple theory covering 2 stroke engines. The other reason I'd prefer a 4 stroke is the relative cleanliness of them, when compared to 2 stroke engines. Now, please don't mistake me for some green nut, but I do believe that if there is something that can be implemented reasonably, to make something run cleaner, then it should be done.

As far as a rotary goes, I believe they are great engines, but I do have to wonder why they're not more widely used? I do know that they are horribly susceptible to over-revving, but apart from that, I'm not sure.

Either way, I think alternate engine options really should take a back seat to the development of an EFI solution.

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