I think engine development is not for the feint hearted, regardless of budget. I know of another Junkers style opposed piston diesel project that was abandoned, and I think it was well pretty well funded. The programmatic problem is often time, meaning where there’s R&D money there may not be time. And then given some money and adequate time, a majority of new technology does not work well enough to go to market.
I’m curious to see what Lycoming’s 205 HP diesel is all about and whether they’d eventually want to sell it for GA. I’ve seen no info other than mentions in a couple of press releases. I’d assume they got DoD funding to develop it but have no idea if that’s true or if the thing is still an early demonstration prototype, to be developed at great expense with Army money over the next 20 years.
Things do get done when funding is available for longer periods. The Shell 100UL development might be a good example. Another is the current application of FADEC with altitude compensation, mixture control etc, which has been in fielded operation in some gasoline engined aircraft piston engined applications for about 25 years. One would hope that eventually there might be a spin-off for commercial GA, certified using the existing reliability database.
I telephoned Mr. Zoche junior today to ask him whether they will exhibit in Friedrichshafen. They have not decided yet, seeing it as a very distracting and physically demanding exercise.
He told me that they have been and they do work full time on the engine, it is not a hobby project. The focus is a diesel-electric variant which has a generator/motor directly in the shaft and allows to physically decouple the motor from the propeller which can be installed in different locations. It also allows the engine to double its power output for a limited time by adding batteries. In this case both the diesel engine and the generator/motor can power the shaft for double output which is useful e.g. for seaplanes at takeoff or helicopters.
The engine has accumulated over 7000h in the test stand. They have not taken investors before because there were several technical difficulties for which they were not convinced that a solution was even possible. They now believe they are past this point and are considering outside funding to speed up development. To put the slow progress into perspective, he made a few points that I can relate to:
- in the car industry, a new engine costs about 1b€ in development and takes about 10 years
- a Formula 1 team spends about 50% of its 200-300m€ annual budget on engines
- despite all effort, none of the countries in WW II managed to develop a new airplane piston engine that went into production (all were using pre-war engines)
- the only other concept coming close to theirs is DeltaHawk and despite the masses of money thrown at it, it is not there either and has a few fundamental issues such as being liquid cooled (which needs 3x the air mass due to lower delta-T and that means drag)
They very much see themselves in the tradition of Hugo Junkers. The goal for power at altitude is 15km just like the Jumo 205. Like Junkers, they are die hard pacifists (Göring confiscated Junkers’ company in his first month in office) and generally refuse to consider military applications. They’re doing the right thing and it will just take the required time until it becomes available is their thinking.
I think the potential is huge, not just in aviation. With the 2-stroke star layout, they can produce a very small practically vibration free engine which could be an excellent electric range extender. In airplanes, it allows constructing twins without large nacelles because the engine can remain in the fuselage with electric motors powering the propellers. The design will probably work well for up to 1000hp and could replace turbines of that size with similar weight but much better SFC. The Jumo 207 produced up to 2000hp (prototype).
It would be great to see humanity get back up to the level of technical knowledge it had in 1934 
A little research unearthed that the 205 HP Lycoming diesel ‘must be’ based on the VM Motori design they bought from Detroit Diesel 15+ years ago.
Here’s an old article: Link
PR says a 45 hr flight was completed a few months ago – no big deal except that it apparently indicates Lycoming has been funded to work on it again. It seems to me that Thielert ownership would now be ineligible to supply western military buyers, so Lycoming has been funded to restart development and took the job in spite of their GA business plan being explicitly based on development of 100UL.
300hp and 271 lbs??
Wow ..where can we sign?
That 1998 article you posted, Silvaire, has one underneath it entitled “Where do we go after 100LL?” which could have been written today
I think ‘where we’re going after 100LL’ is 100UL, because it’s the best technical solution. Diesels will be the very expensive, low volume solution for owners operating where there is no AVGAS distribution – like the US Army. Army programs have had terrific problems with engines BTW, first the Guzzi then the Thielert, and who knows how this Lycoming diesel will work out. At least they (the US Army) are spending money on GA applicable technology.
I kind of like the idea of my 150 HP O-320 being instantaneously good for 10% more power, or 165 HP… Especially so since a different version with higher compression pistons has already documented reliability at 160 HP.
Sooo… if one fuel has a different density… (and supposedly different mpg) how does one calculate range and endurance when mixing fuels?
@chrisparker – ETP calculation would become an interesting exercise ^^
Shorrick_Mk2 wrote:
Sooo… if one fuel has a different density… (and supposedly different mpg) how does one calculate range and endurance when mixing fuels?
Yes, this sounds really weird. 0.5 to 0.8 pounds per gallon is in more understandable terms: 0.060 to 0.096 kg/liter heavier. 100LL has a density of 0.718 kg/litre. So this new fuel will have a density of:
0.778 to 0.814 kg/litre. The strange thing with this is that Jet A1 has a density of 0.804 kg/litre. This new fuel could be heavier than jet fuel
