engine

[Torkel]

John Slade, can you tell how much your engine weights including cooler,and also use of fuel for diff. hp setting, I have heard that the rotary use a lot of fuel, otherwise very reliable. I have search info on this on diff. forum but can`t find it.

[John Slade]

Hi & welcome,
With the turbo, coolant and oil, oil coolers, radiator, intercooler and other accesories I think the 13B weights in at about 360lb. I don't have a clear idea of fuel burn yet, but it's clearly not ridiculously high. Other rotary flyers (Tracy Crook) have reported similar fuel burn to Lycomings. Since I'm using auto gas rather than 100 low lead the net cost per mile is much lower with the rotary.

[ShaleDC]

I'm no expert, but tests have shown that a well-leaned Mazda Rotary engine will produce the same hp/lb fuel as a Lycoming when running rich.

In terms of fuel burn alone, it is an indisputable fact that the air-cooled lycoming is more efficient. By leaning the Lycoming, it WILL BE more fuel efficient than a well-leaned rotary. However, you have to consider overall lifecycle costs. Running lean of peak with a lycoming will reduce your TBO, at significant cost, which may exceed the fuel savings. Once you consider all life-cycle cosst, including installation, maintenance, overhaul, fuel options (93 vs. 100LL), then the Mazda rotary appears to meet or exceed the cost efficiency of the Lycoming.

Turbocharging the Mazda rotary allows you to increase the overall fuel efficiency, at increased install/maintenance cost. A FADEC system that allows you to constantly run lean-of-peak (like the MISTRAL engine) is another way to maximise fuel efficiency. These two options will likely allow you to approach and meet average Lycombing fuel efficiency in most applications.

[Dust]

Originally Posted by ShaleDC

Running lean of peak with a lycoming will reduce your TBO

Not from the reports i have read. running rich causes crap to condense out of the exhaust and coat the exhaust valve, causing wear, running lean stops this and reduces wear. I personally vacuumed this stuff out of my engine when i removed the exhaust

[Marc Zeitlin]

Originally Posted by ShaleDC

.... Running lean of peak with a lycoming will reduce your TBO.....

I agree with everything you wrote except this one sentence. Everyone should read Deakin's articles on Avweb at:

http://www.avweb.com/news/columns/182179-1.html
http://www.avweb.com/news/columns/182176-1.html
http://www.avweb.com/news/columns/182583-1.html

In which he debunks this myth (as well as many others, and gives a wealth of useful information on how to treat aircraft engines).

[ShaleDC]

hmmm. Well as I don't own an aircraft, I can't speak from personal experience on Lycoming TBO.

Perhaps the origins of the myth are in that some people don't lean correctly, leading to detonation, burned valves, etc... Cooling on many GA aircraft is very shoddy, with wide dispersion in temps between cylinders. Lean of peak on one cylinder isn't neccessarily LOP on the others.

My impression has been that the Rotary is much more forgiving of the inherent inaccuracies of EGT/CHT sensors and their temp dispersion, allowing safer LOP operation.

(Of course, with poor cooling and unreliable EGT/CHT sensors, running rich is no guarrantee of TBO either. Those problems are going to manifest themselves in clogged valves, etc...) The real issue isn't the core engine, it's the complete install package and operator feedback/response.