Using truck diesels for Beaver-type large Bush planes. Perfect match?

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sming

Well-Known Member
I was watching this pretty interesting and entertaining series on a duramax by Banks power and remembered this thread, so, there it is:
711 HP @ 3300 rpm, that would work direct drive!

PMD

Well-Known Member
Most of the correct answers/comments have already been posted. The Orenda (Trace) 600HP V8 was aimed directly at the ag engine, DHC-2 and DHC-3 market. There was a conditional approval given to the Beaver installation. It weighed maybe 100 lbs. more than the AN-14B installation, but had much better power and fuel consumption, so a fantastic tradeoff. In my days sitting between a pair of 985s, we would never have considered an engine swap as there were endless new engines in the can for just over ten grand a pop, and the airplanes themselves were very cheap. Today, with the supply of Pratt's and avgas drying up, and the value of the airframes going through the roof, it DOES make sense to look at alternatives. That said: note that Trace is tits up, so nobody taking it seriously on the gasoline side.

The light and medium truck diesels I have a LOT of experience with. NONE are anywhere near the power/weight potential as an installed engine with drive, cooling, etc. What IS very true is the limit of any modern diesel is its mechanical strength, as you can make any level of power you want with ease. The idea that an ancient design such as the GM 6.5 is nonsense, that is a pre-chamber, indirect injection engine, and even in their lowest power level and lightest use usually end their lives because the main bearing webs are cracked. I could write a book (I have written several articles) about the design deficiencies of the IHC DT444 (i.e. 7.3 Ford Powerjoke) as I have had to make them run in trucks at continuous power levels similar to what a 4 to 6 place airplane would need. They don't last long at all under such conditions.

Someone wrote about the German diesels, and yes, they DO have some potential (Audi 4.2 V8 for example, and similarly their 3.0 V6 TDI). Those two ARE light enough to be candidates for 300 and 200HP conversions, but still, they are automobile engines not really well suited for aircraft use. Take a moment to remember that using a M-B diesel in Diamond aircraft took Thielert out of business. Worth noting that in that sub-300 HP range, there is already a SMA at 230/260, but check the installed price in a C182 for a Soloy conversion - something approaching a quarter million bux!! The real possibilities for a 985 replacement diesel are right around the corner: the 460 CID 6 banger being certified by SMA just below the right power range at 350-375 or so, the fantastic 8 cylinder EPS also nearing certification at an initial power level (of 375 maybe 400?). What IS common to ALL of these certified or near-certified diesel engines, though, is they are all extremely expensive and heavier than their equivalent gasoline piowered targets.

Forget the truck engines: if you want a prediction that we can come back to in several years - the ONLY diesels that will be able to cover the 400/500 HP class and come in light enough to install in existing airframes will be an opposed piston, 3 cylinder/6 piston design. Not having the weight, size and heat loss of a cylinder head is what tips them over the line. Would have been impractical/unlikely until the current level of HPCR tech brings them out of the '50s/'60s closet and thrusts them to the front of the line. For some interesting reading, google "Achates Power" and you will get a few glimpses of the future.

Doggzilla

Banned
HBA Supporter
Thielert actually did really well until the recession screwed everything up, as it did for countless others. They got bought by Continental and the 2.0 liter diesel is still available.

In fact, they just flew a 310hp that is scheduled to be available near the end of 2020. The Continental CD-300.

Doggzilla

Banned
HBA Supporter
Also, GM released a new block for the 6.5 to address the cracking and cooling issues. I believe it was around 1997.

Anyways, those issues arent anything that cant be fixed. There are plenty of companies capable of producing better blocks for lighter weights.

TarDevil

Well-Known Member
Thielert actually did really well until the recession screwed everything up
Well...300 gearbox intervals was the bigger culprit.

PMD

Well-Known Member
Yeah, it was the gearbox more than the economy for Thielert, no doubt there.

The indirect injection engines (i.e. 6.5 GM) have no chance of approaching the efficiencies of a HPCR (High Pressure Common Rail) engine. The main issue is accuracy of timing (a less than miscibility pressures, entrained air means wild inaccuracies of lower pressure diesel fuel systems), followed by the inability to "rate shape" (make inection duration fit the desired MEP curve) and finally lack of the kinds of pressures it takes to get good atomisation (something like 25,000 psi now). It was easy to get big power from direct injection diesels in years gone by, but looking at the plumes of smoke from a tractor pull (or looking in the mirror of my own 6.5 and 7.3 trucks) gives you an idea how poorly combustion was controlled. Modern HPCR engines can make dizzying levels of power with very clean combustion. Just drive any one of the big 3 2020 one ton diesel pickups and you will get that message (fell it but not smell it).

All of those things play into how "boing-boing" 4 strokes work, but work even better in a uniflow 2 cycle, especially with opposed pistons (archetcture of bore/stroke and lack of cylinder head exceptionally good for such a diesel). In case it is not intuitive: the two opposed pistons allow ideal bore/stroke ratio without excessive piston speed. the lack of cylinder head means far, far better gas flow potential and no waste heat radiated from a structure that is simply not there.

PMD

Well-Known Member
In fact, they just flew a 310hp that is scheduled to be available near the end of 2020. The Continental CD-300.
Yes, Frank Thielert started on that project a LONG time ago (IIRC, bot the 4.2 V8 and 3.0 V6), and that was one of the things that killed his business (that, and the gearbox life). Adding Continental and AVIC to the mix should mean this engine will be done correctly and suported fully. I believe the CD-300 already has EASA certification. Haven't seen the nubers yet, but strongly suspect it will suffer from some of the SMA/EPS/CD135-155/Austro170/180 problems - far more installed weight and cost than an equivalent legacy Cont/Lyc air cooled engine.

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timberwolf8199

Well-Known Member
What about some of the smaller diesels out there now? I don't know much about them but I've heard claim on the internet that the new ford 3.0L can produce 350 hp and 600 lbft with a weight under 600lbs (505 lbs for engine w/ oil, plus coolant, etc). Supposedly possible with just an emissions delete and a tune.

Also, I thought it was interesting to hear billski's perspective. My grandfather used to work for International and the version I heard from him was that the specs were changed after the development was essentially finished. That International told Ford it wasn't designed for it, but that they decided to move ahead with the new ratings on the existing design with a few tweaks to get the output they wanted.

B100

Well-Known Member
I just checked some numbers...

Ford Scorpion Diesel - 450 hp, 1100 pounds wet. Doubtless the cooling, induction, and exhaust can be lightened up some. It will still need a suitable prop bearing set to carry prop thrust and gyroscopic forces so add some wieght back in for that;

Wasp Junior R985 - 450 hp, 653 pounds wet.

Maybe someone else's 450 hp diesel is lighter, but it sure looks like there is a big weight penalty for this combination. I give much better chances to the GM big cube LS engines with a decent PSRU as a suitable replacement for the R985.

Billski
You want a good diesel for those specs ? Europe is the place ...perhaps this one would do the job ...as is or with a chip/remap ?
4.2 V8 TDI CR 235-257kW -
dimensions
length: 520 millimetres (20.5 in), mass: 255–257 kilograms (562–567 lb) CTEC: 283 kilowatts (385 PS; 380 bhp) at 3,750 rpm; 850 newton metres (627 lbf⋅ft) at 2,000-2,750 rpm

PMD

Well-Known Member
Gee, I get so wound up when this topic comes up, I think I completely forgot to mention EPS.

The 4.3 litre "flat V8" uses Euro (BMTroubleyou) tech/geometry to make an easy 320 - 450 HP. Two comments: at launch (385HP) it will be heavier than an same power 540 and even heavier than an IO-720 (circa 600 lbs. for all of the foregoing). The thing one needs to appreciate about ANY diesel is that you can have more power at the same weight by simply adding more air and fuel. The limit is the structural integrity of the engine - which for aviation use is set at considerably more conservative values than a truck or car. EPS now mentions that their new engine is intended and capable of reaching the 450 HP level - so there you go, a diesel that meets the exact power/wt ratio of an AN14B.

Now, let's address the Viking PT6 conversion of the Beaver. It involves stretching the airframe to get CoG right - and increase cabin volume and gross weight to 6,000. WAY more power than the P&W recip, but at a million  more, it is simply not the same airplane at all. If you just bolt a PT6 on the nose (as others have done) you CAN make a direct comparo. The turbine...under IDEAL conditions can burn as little as 0.67 lb/hp/hr. Problem is: Ideal conditions are no where near the altitudes flown in a Beaver - and turn down performance (i.e. operating at less than ideal load) on turbines is horrible. Real world, I doubt anyone has ever seen .75 lb/hp/hr from a turbo Beaver. That is about TWICE what a diesel can do (an inefficient diesel with a cylinder head...won't even get into opposed piston diesels at this stage). So, think of the EPS engine when it gets certified at 450 HP in terms that it needs to carry 1/2 of the fuel of a PT6 powered same plane. Hmm. Also, the EPS engine will come in a bit over a hundred grand, so let's call it $200 installed. Not bad. A HELL of a lot less than a PT6. And, yes, PWC stuff is reliable, but wait until you check out the price of those mandatory hot section and other periodic maintenance bills! So, very, very soon (EPS expects certification this year) you CAN hang a certified engine (at 385 right now) on a Beaver (or in my wet dreams, a pair of them on a Beech 18 and an Aerostar). You won't have to rip the Cummins out of your 5500 Ram. And it will be as good as or better than a turbine powered one of equivalent horsepressures. (again, note that the Viking DHC2T is a different airplane - and a very, very good one at that). PMD Well-Known Member Oh...and I didn't go anywhere near the automotive drop-in for the purpose: Audi did a 6.0 litre V12 in Euro versions of the Q7. Just take it out of the box, hang on a re-drive (yeah, I know, none exists) and there you have it. A dirt cheap, dead reliable and easy 500++ HP for a homebuilder. Of course, you could take the easy way out and just buy a RED V12 diesel, EASA certified at 500 HP and all up weight of 700 lbs. for something around$200k.

There is a LOT (and a lot more you don't see) going on with diesel aircraft engines...for very good reason.

thjakits

Well-Known Member
...that would be the RED A03 - 12 cyl...
I think there is also a RED A05 - 6 cyl.... not sure it is real yet, but at least on the drawing board - basically a 1/2-A03....

thjakits

wsimpso1

Super Moderator
Staff member
Log Member
4.2 V8 TDI CR 235-257kW - dimensions length: 520 millimetres (20.5 in), mass: 255–257 kilograms (562–567 lb) CTEC: 283 kilowatts (385 PS; 380 bhp) at 3,750 rpm; 850 newton metres (627 lbf⋅ft) at 2,000-2,750 rpm
Hmm, 627 lb-ft at 2000 rpm is 239 hp, 627 lb-ft at 2750 rpm is 328 hp. At 2000 rpm, that is pretty anemic for hauling a Beaver about. At 2700 rpm, you might be OK, but an 8' prop for such a beast is supersonic. To get to takeoff power of 385 hp and 3750 rpm and a reasonable 800 ft/s tip speed, you need the prop down around 1900-2000 rpm. That is a reduction ratio of 1.9:1

Any idea what a durable 1.9:1 PSRU that will handle that level of power, torsional vibration, and gyroscopic moments will add to the mix? You can not just connect the gas engine drives for more modest vibration to this diesel, it has about triple the torsional inputs that a normally aspirated LS engine has. This experienced powertrain engineer is guessing more than 100 pounds, if you can find such a beast for it. So this still is approximately 100 pounds heavy as a drop in.

Then there is the issue of length. How do these engines compare to an R985 from firewall to prop flange length?. If they are heavier and/or longer from firewall to prop, you would also have to do something significant to balance the thing as well.

When you get a suitable diesel engine, PSRU and deal with the weight, length, etc, let's revisit cost again. Until then this is just dreamland.

Billski

PMD

Well-Known Member
Couldn't agree more with Billski. Length (configuration) and weight with re-drive is why auto conversion engines (such as Thielert) don't work all that well as retrofits. Keep in mind: the PT6 has a completely different set of problems, and the Viking solution is to literally make a different airframe to suit. No to easy to move the wing forward to compensate for a V12 though. None-the-less, the Orenda/Trace V8 was installed in both Beaver and Otter airframes without (I think) any major changes.

BRW: IIRC one of the selling points to do the Beaver STC for Orenda was that the naturally aspirated gasser had better climb and speed at altitude than the PT6, never mind a HECK of a lot better fuel consumption. Of course, most Beaver pilots considered any time they were above (most of) the trees they were already high enough.

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AIRCAB

Well-Known Member
I was watching this pretty interesting and entertaining series on a duramax by Banks power and remembered this thread, so, there it is:
711 HP @ 3300 rpm, that would work direct drive!
Why not go with Duramax. The Beaver has a STC for GM gas engine (Trace).