Lets talk about diesels.

Discussion in 'Firewall Forward / Props / Fuel system' started by Terrh, Oct 17, 2019.

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1. Oct 17, 2019

Terrh

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There aren't any recent diesel-specific threads, and I've got diesels on my brain right now.
What I don't want in here, is "diesels are a stupid idea". If you think that's the case, please just move along.

What I would like to discuss is:
Available diesels in N.A. (or mail order from china) that might prove suitable in a homebuilt aircraft. Say from 50 to 200HP range.

Mazda has a recent one - the "skyactiv-d" that is all aluminum, extremely light weight (can't find numbers though) and should be available in junkyards cheaply within the next few years. Reliability is still an unknown, and so is figuring out how to make the computer work outside of a car, or using an aftermarket computer on it at all.

The Chevrolet cobalt also came with an all aluminum diesel recently - though I can't find much about it.

I've looked into the recent chrysler/mercedes V6 diesels and think they're too heavy to bother with, it really looks like straight-4's are the only automotive option with any sort of reasonable weight.

Anyone know of any air cooled options? Or other motors, please link to them/discuss their merits and potential issues in here.

2. Oct 17, 2019

BBerson

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3. Oct 17, 2019

Hephaestus

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4. Oct 18, 2019

galapoola

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According to that, 320 N⋅m (236 lb⋅ft) at 2,000 rpm. This probably could run direct drive with a proper thrust bearing. Wonder how much it weighs?

5. Oct 18, 2019

Hephaestus

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6. Oct 18, 2019

PMD

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At the risk of violating the OP's original premise for posting: An automotive diesel engine conversion for homebuilt use is not a great idea. Let's be honest: Thielert blew a lot of millions down the drain showing why even a company with deep pockets (empty ones now) and strong engineering background end up when using a 4 cycle 4 banger with a massive gearbox that is extremely difficult to make tolerate the torque reversals and harmonics of 180 degree spaced power pulses. What is needed at the 100-200HP range is a genuine bespoke aircraft diesel. A converted 4/4 auto engine, IMHO, is a really bad idea - even if Continental (Thielert) and notably Austro (Didamond) have production, certified versions. Two big problems: they are too heavy and they are too expensive (for the real world where most of the airplanes we own, fly and build are worth only a fraction of the cost of such an engine).

When we look up the scale where the big activity is (200-400 HP) SMA engines are to my mind as close as you can get to hitting right on the mark, but you can't yank a little Lyc out and hang the monster 305, you need to be looking at Skylane gross weights and a 6 banger boat anchor under the hood before you can slip over to Soloy and drop **** near a quarter MILLION  to hang it on. EPS has really gone to the head of the list for the over 350HP market, but while they have enough power pulses to be able to use a metal prop (note: not something a 4 banger diesel CAN do!!) check the weight - STILL going to be a stretch to squeeze it into and Aerostar (but what a fantastic thing a 800HP 702 would...sorry....WILL be!!!!!)

So, here we are with relatively small pockets with 100HP market dominated by what has become an expensive and complex SI engine (Rotax family) that can't burn a safe fuel (i.e. diesel or Jet).

One of the AVIC fully owned subsidiaries (forget their name off the top) is about to launch a 150HP 4 cyl opposed (boxer) aircraft diesel with a drive reduction that is IIRC lighter than an 0-320. Worth noting that China owns by far the largest portion of actual aircraft diesel production, so don't ever forget they (with horrid avgas availability) are THE driving force.

IMHO, the ONLY real promise at 100HP is opposed piston diesels. They already have a gear train, no problem at all to put a thrust bearing in the mix to drive a prop and ANY speed you would like. Far, far simpler, can be Rotax light with ease, MIGHT be able to be built cost effectively (simple design, very low parts count). These are 100 year old technology, not new stuff, but as high speed small engines, THAT is where the new developments are and need to be. Sadly, the only 3 banger around was bought up by Chinese (Superior) and after a big intro splash - passed into oblivion. My forecast is that SOMEONE will step up to that plate and go where nobody has yet arrived and bring this technology into our little corner of the universe.

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7. Oct 18, 2019

Terrh

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PMD, I appreciate it. I just don't want this to turn into a naysayer fest is all.

There are maybe some light-enough options. The modern auto diesels are all aluminum and while I'm sure they're heavier than an aircooled gas engine, they should be light enough. Even adding 100lbs of engine and losing 100lbs of payload wouldn't make an airplane unusable, yes it would suck but it would still work.

The Smart 3cyl I had forgotten existed, they are cheap and abundant here, and apparently have been used with success in germany. I feel like the biggest hurdle with modern automotive diesels will be finding a computer to control it and eliminate the emissions stuff. It would obviously be bad if an airplane demanded a regen mid flight.

The new GM diesels - I'm excited that they come in the terrain/equinox, I'd love to find out how much they weigh. They should be extremely abundant within a few years, and someone will probably find a way to unlock the ECU quickly.

I've got the machine shop and the tools/engineering skills to build a PSRU, and am wanting something for a winter project this year or next.

8. Oct 18, 2019

Terrh

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Anyone know anymore about flyeco? No website updates in a long time. http://www.flyeco.net/
I do wonder how they are getting 80 reliable HP out of the engine, that's double the output of the early ones. Even the "best" ones (800cc) are 53 factory HP. I'm sure they can make that amount of power all day long, but much beyond that I'd start to wonder.

9. Oct 18, 2019

Hephaestus

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With the current ecu options, this isnt a huge challenge. Its not mechanical changes required most of the time now its plugging in a non factory ECU and setting it up to work the way we want. Imagine this discussion in the 70s and trying to adjust & tune a mechanical hpop and injectors to get the needed changes.

Id love to see more development of the om660. They seemed to pop up and disappeared almost immediately. Not sure if the market just wasnt there or its just the turnaround time on installing a fwf package?

10. Oct 18, 2019

sming

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Hello, I believe you've heard of the gaz'aile project? It flies with a 53HP 1.4 diesel engine from PSA. Prototype flew with a Isuzu TC4-EE 1.7 from Opel. Current development is 100HP 1.6 HDI, still from PSA.
Mechanical injection pump with custom belt PSRU with rubber donut for harmonics damping. At least 50 gaz'aile are flying, not all with diesel. I believe no PSRU failed yet...
http://gazaile2.free.fr/indexAnglais.php
http://gazaile2.free.fr/englishInformations.pdf
I've started (kinda. made one piece, the firewall plywood plate) building one, and live in the same town as the designer, so feel free to ask questions if you don't find enough information in english.

On your side of the pond, an article in Kitplanes: https://www.kitplanes.com/alternati...xrKLTslKjULQ0Q45Y9_QXMoThbXxMyGCxzz8Rq0v98Xmk

Coming back to the 3 cylinders smart engine: It's been tried here, with the Greenelis project (https://www.aerovfr.com/2016/03/le-retour-du-greenelis/). It's a gaz'aile fuselage with different wings and a retractable monogear, built to race in the CAFE foundation 2011 Green Flight Challenge. They couldn't overcome the torsional vibration problems of the 3 cylinders with a design based on the gaz'aile one so good luck if you go down that road!

Last edited: Oct 18, 2019
11. Oct 18, 2019

sming

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What ECU options ? I've been doing quite a lot of research and I cannot find something Megasquirt like for diesel ECU. Options are Bosch Motorsport for 6K€, the Motec M1 of Raptor project fame is more than 4K€, and what you will find with google is always around 2-3K€ or equivalent. The cheapest I've found was 1.5K€ and I'm not sure it was really available. If you got something, I'm all hears!
That's why Serge Pennec convert the HDI engines to mechanical injection. It's doable by homebuilder and your engine will run until it runs out of fuel or until the pump fail, quite safe if you ask me...

12. Oct 18, 2019

Hephaestus

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Maybe im wrong on the diesel front. None of the options are dirt cheap - but I'm pretty sure there are a few megasquirt derivatives that'll do some level of diesel.

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13. Oct 20, 2019

Terrh

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I don't think that there's any options for diesel ECU's short of reflashing OE ones. Not that that should be a problem, as long as an aftermarket flash for it exists. Or in the case of non emissions diesels, maybe nothing at all needs to be redone.

14. Oct 20, 2019

cheapracer

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Just in case you weren't aware, 1 pound of carbon fiber weighs the same as a pound of aluminium, that happens to weigh the same as a pound of iron. Just because something is made of 'X' material, doesn't mean a thing about it's weight.

So how about next time you "can't find the numbers", just don't post guessed nonsense thanks, as I prefer a discussion based on factual information.

"extremely light weight" aluminium 2.2 turbo-diesel Mazda @ 480lbs
'god darn heavy' cast iron Ford 5.0 V8 @ 460lbs

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15. Oct 21, 2019

Geraldc

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DV6 Diesel motor as used in Peugeot Ford Toyota modified for Airplane with reduction drive turbo and oil weighs in at about 110kg or 240lb for at least 100 hp.
Skyactiv-D may be less because it has the compression ratio reduced to 14:1 saving 66lb 30kg over cast iron block and exra weight savings in rotating parts etc.

16. Oct 21, 2019

cheapracer

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The weight of the Mazda Skyactiv-D is 480lbs, so yeah, maybe less than 2 x DV6 engines. Likely that includes air con and steering power pumps, and flywheel, but still heavy.

The Subaru Diesel weight is well known at 175kgs/380lbs, that's stripped down for aircraft, ready for PSRU, which I would suggest the Mazda is close to also stripped to bare requirements.

Then you need to add cooling systems, water air and intercooler and PSRU weight, so 40 to 50 lbs.

17. Oct 21, 2019

PTAirco

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I have had the idea of Diesel aircraft engines simmering away at the back of my mind for decades now. I really think that two stroke diesels are the way to go. It instantly eliminates one of the major drawbacks of diesels: power to weight ratio. Plus it simplifies things mechanically . It's almost a no brainer.
NASA did a study on two stroke diesel engines for GA, you can find it if you Google it. Extremely interesting.

https://ntrs.nasa.gov/search.jsp?R=19800011788

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18. Oct 21, 2019

stanislavz

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Some more info on that moder aluminium diesels - they are designed with minimum compression ratio, to allow mechanical simplification (two compression rings in place of three, aluminum block, etc.. ) PSA tried this without lowered compression on their 1.4 which is used on gazaile - and it had some torsional problems with engine. Later engines were made from cast iron...

Another ready to use small diesel in sub 100 hp is fiat 1.3 jtd. At least 4 banger..

I would use a subaru boxer with same lowered compression, to relieve load on parts.

19. Oct 21, 2019

Terrh

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Where did you find the Skyactiv-D weight?

Which generation and displacement skyactiv-d engine is it for?

I still think the GM MDE will be a better route to take then this one, but the weights on both is currently unknown as far as I can tell.

Last edited: Oct 21, 2019
20. Oct 22, 2019

thjakits

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Hi all,

AFAIK - the Skyactive-D has NO sparkplugs. It reduces cylinder compression pressures and high pressure fuel dispersion to make a better/cleaner burn. Less pressures result in less weight for the engine and the dual turbo (incl. variable vane tech) make it a smooth and quiet engine...

However - it is made for cars... so the requirements are different to aviation.

At the end - I believe the way to get around to use Jet-A is to convert "gas engines" to burn "spark ignited Jet-A".
Basically existing engine structure could be used - NO higher compression pressures than in a gas engine - multiple-spark ignition concurrent with fuel injection into the cylinder - with todays very-high-pressure fuel system and presently used injectors it should be possible to disperse Jet-A - just like Diesel - into easily ignitable very fine mist.
If the compression ratios were to stay below self-ignition levels, a controlled/designed burn/flame-front should be possible with present tech...

We know that gasoline engines do a decent job - I think available technology can enable the use of Jet-A in similar engines....

I think it is never going to be easy (...especially financially...) to adapt a car engine for aviation duty, diesel or gas. People try to lower weight and squeeze out x2 or more of the design-cruise-power of that car engine - and that's where things become "interesting/complicated".
The application closest to Aviation power-use-profiles would be Marine applications and power generators.
There are nearly NO engines that got picked from cars and put into boats. Any and all similar configurations are just that: A V6 is a V6 or a V8 a V8, but there it ends. If you compare Marine-designs, they are usually very much sturdier, heavier and a LOT more expensive! Except for a few short hours in a racing application in a small boat you won't find "car engines" on the water...
[I hear Jet-boat-racers, the small 2-seaters on twisted circuits are fond of Lexus V8s...]

A more practical approach to see the capabilities of a specific engine towards constant power output would be to look at gen-packs! Usually the speccified power output is some 15-20% LESS than advertised in the car brochure!!

So - if you want to apply this, one would need a 400 hp engine and reduce USE to 3020 hp max!! (...you still got the 400 hp available for short sprints, just like in the car!)
That's what Robinson did in their piston powered helicopters! Take a big, but already low-power airplane engine and reduce power usage another big % - 260hp engine derated to 225hp for 5 min and constant 205 hp. That's how these engines now last longest in the Lycoming lineup.... - I still got the 260 hp if the situations asks for, but at least in helicopters, if you are not out of "....a situation" in 45 sec, you won't get out....so, the transmisison can take 260hp just fine, just not for unlimited time...

Going this way with TRANDITIONAL Diesels is not going to work, because of the involved weights...

So - why not try to go the other way and use a lightweight "gasoline piston engine" and make it use Jet-A...

Maybe I am not aware of possible problems - spark plug errosion or carbon buildup or ???

Cheers,

thjakits