A Little Eggenfellner History

[SvingenB]

Well, it is only a couple of years ago that 10,000 faulty certified ECi cylinders had to be replaced after 800 h on certified Lycomings with 1800 h TBO. After 50 years, and they still haven't got it right It was FAA that finally issued the requirement for replacement, and the customers had to contact ECi in Texas themselves. How many experimentals are still flying with these cylinders without even knowing about it?

In contrast to Lycoming and Continental, Thielert has a constantly updated user database. For isntance in 2005, 80 clutches were replaced by Thielert, free of charge by sending out mechanics. The engine computer together with the customer database enabled Thielert to sort out other possible problematic clutches based on three incidents within hours, and contact all the customers within 48 h, all the 80 clutches were replaced within one week (If the FAA/EAA had to be involved, this would have taken months). They could do this without first investigating the cause of the error. They only knew that the three engines of concern had recently had a clutch overhaul, and so had the other 80. Later they found that the error was due to several people using wrong cleaning agent when overhauling the clutch, leading to a chemical reaction of the surface which changed the friction number. This is the same support principle as RR, GE and PW uses together with most car manufacturers. Why aren't Lycoming using it? Why do Lycomings, a 50 year old design, cost so much as they do when they are not offering something even close to this level of support?

Things happens to everyone, but to achieve 3000 h TBO can only be done in full openess and close cooperation with the customers. Thielert is doing this, Lycoming is not.

I cannot say anything about the gearbox of the Thielert, but it looks like the whole package originally is designed with very small margins to get the weight down. The engine itself (the 1.7 L) comes from a MB A-type that in the car only produces 90 HP max. In the airplane it produces 135 hp continous. The 2.0 is probably much better (or easier to get right) and it also has a lighter gearbox. A clutch is probably needed. This is a diesel with a tremendous torque (very high power peeks) at low RPM. It probably has 200 Nm already from 1200-1300 RPM, or maybe the FADEC limits this?

There are some other diesel conversions in the 100 HP range meant for the uncertified market. eco-motors. 1.4 L TDI engine (PSA? VW?) with 80/100 HP to be used as a replacement for Rotax. Compared with Rotax it weigh 24 kg more or approx 30% more. eco-fly (why this eco-xxxx ? ). This is a converted smart engine, also as a replacement for Rotax, but it doesn't look like much is happening there.

Then there is the Raptor. A turbodiesel made from the ground up to be an aircraft engine, but have not been flown. They claim 105 hp at 81 kg at 2800 engine RPM. At 2800 RPM, only 1.55 L and no intercooler, this is hard to believe, but who knows.

I would place the Egg well below the eco-motor regarding technical complexity, more in the class of the hundreds of BMW conversions flying. When Jan makes a conversion with the new diesel Subaru incl a gearbox that can manage the diesel pulses, and within weight limitations making it flyable, at the right price (preferably way more economically than a gasoline engine), then we can start comparing the Egg and the Thielert. With the same logic, the Egg (existing gasoline conversion) is probably at least just as good as the Thielert is today

[rv6ejguy]

Thielert's level of support does not get rave reviews in either the TAC story nor by operators or Diamond dealers. Tardy response, long wait for parts and even arrogant attitudes have been mentioned. My understanding is that Diamond is often handling the problems with the customers directly.

You'd never want any sort of clutch to be used near the max torque output of an engine to couple to the gearbox. This is a sure invitation to speedy failure, especially using a limited travel loading device for the disc.

Thielert is examining plenty of fragged parts coming back to them so they should be able to assess failure modes and design fixes.

In the case of the clutch problem here- yes the problem was detected by auto switching of the FADECs with a crank sensor code. Removal of the sensors revealed metallic parts and rust dust. Diamond authorized the removal of the PSRU to have a deeper look. Good thing the FADECs have decent diagnostics- this saved a thrust loss a few hours down the road.

Contrary to popular belief, diesel engines do not produce staggering torque levels because they are diesels, they do it because they are heavily boosted. Take away the turbo and this engine would be lucky to make 110 ft./lbs.

[SvingenB]

Originally Posted by rv6ejguy

Contrary to popular belief, diesel engines do not produce staggering torque levels because they are diesels, they do it because they are heavily boosted. Take away the turbo and this engine would be lucky to make 110 ft./lbs.

A diesel without a turbo is like an airplane without wings A gasoline engine only increases power when turbocharged (with intercooler preferably), a diesel increases both power and efficiency. Still, on low RPM (idle), the turbo is not producing any boost, but the torque is much higher than a gasoline engine due to the 18:1 compression ratio instead of 9:1. Anyone with manual transmission and a diesel engine driving at rush hour for work can subscribe to that. No need to use the gas pedal, only clutch and brake. Without a turbo, the torque usually peaks at 1500-2000 RPM and decreases sharply after that. With a turbo, the torque on modern diesels also peaks at 1500-2000 RPM (although at a much higher value than without a turbo), but stay there untill 3-4000 RPM or even higher.

The original engine used in the Thielert now (2.0L Mercedes for the A-class, the A200) has 140 hp at 4200 RPM. Max torque is 300 Nm, and this is constant from 1600-3000 RPM. The gasoline powered version (2.0 L) also has 140 hp at 5750 RPM, but a max torque of only 185 Nm at 3500 to 4000 RPM. The turbocharged 2.0 L gasoline engine has 190 hp at 5000 RPM, but "only" 280 Nm torque at 1800 to 4850 RPM. The engine controller of the Thielert is probably nothing like the original from MB, but this gives a rough picture to compare a turbo-diesel with a normal gasoline engine of same displacement.

[DanH]

Think about it gentlemen. Mean torque means almost nothing in the context of this clutch and clutch's purpose in the system.

[SvingenB]

Originally Posted by DanH

Think about it gentlemen. Mean torque means almost nothing in the context of this clutch and clutch's purpose in the system.

That was what I was thinking about. You explained earlier about angular vibrations, ressonance and power pulses at low RPM. A diesel with larger pulses must be harder for the gear than a gasoline engine. How much, I am not sure, but certainly larger.

[Rotary10-RV]

Hi Guys,
Don't you think we might start a Thielert thread? I love the idea of a good diesel, and I think that Thielert has the engineering horse power to make the engine function properly. It does seem that aircraft diesels are an idea whose time has come for GA. The original thread though was about the history of David and his approval of the Eggenfellner Subaru. There are several aircraft diesels that are worth discussing on their own merits. Lets start one.
Bill Jepson

[SvingenB]

Originally Posted by Rotary10-RV

Hi Guys,
Don't you think we might start a Thielert thread? I love the idea of a good diesel, and I think that Thielert has the engineering horse power to make the engine function properly. It does seem that aircraft diesels are an idea whose time has come for GA. The original thread though was about the history of David and his approval of the Eggenfellner Subaru. There are several aircraft diesels that are worth discussing on their own merits. Lets start one.
Bill Jepson

Good idea The more I think about it, the larger my headache becomes when fuel cost will be reduced by 50-70 % by going diesel. Here in Europe, we are almost to the point where a similar hp turbine burning Jet fuel would be cheaper to run than a O-360 burning AVGAS (if we have not crossed that point already).

[CraigC]

Being an EAA'er for a long time, and an A&P even longer I can see the benefit to pushing the envelope. Nothing good comes from staying inside the box. We would still be riding horses to work (and might be again soon!) if nobody tried something new. That being said, there should be in bold letters a warning to any that want to buy these engines. They are not for the inexperienced and faint hearted. I really would not care if every jet jock and throttle actuator from here to wherever bought an experimental engine. It is just that, experimental. Taking something designed for 2 dimensional road use and putting it in the air with positive and negative g's, different cooling airflow than planned, and different hot spots for accessories are just a few of the major issues I see. And, I don't see where using fighter pilots and airline pilots as standout early adopters really helps the case of safety. Unless they are engineers and can design their own test program and know what they don't know and how to find an answer it won't help.

[janeggenfellner]

Taking something designed for 2 dimensional road use and putting it in the air with positive and negative g's, different cooling airflow than planned,

Very true but your statement does not at all account for the 16 years I have been flying nothing but Subaru Aircraft engines.

Jan Eggenfellner

[CraigC]

Jan,

I did not say it should be outlawed. Just that there are still big "what ifs" to find. That was also true of early aircraft engines of all types. There is a lot left to learn on adapting these kinds of power plants to aircraft. As long as those that use them understand that every hour they fly is a flight test, more power to 'em. For those that think you can hook up, mount up, and blast off IFR over bad terrain and all kinds of weather I would say, good luck, be careful. Sixteen years is a start...

Very true but your statement does not at all account for the 16 years I have been flying nothing but Subaru Aircraft engines

Sixteen years is good. When there are 100,000 subies flying and they are hitting TBO with failure to success records as good as the legacy engines, that will be cool.