D-motor from Belgium

[Timberwolf]

Same mount as a jabiru. 2.9 gal/hr 80 hp.

http://www.youtube.com/watch?v=wxK_G...eature=related

Weight sounds optimistic, as does the fuel flow.

[N714SM]

After further looking at the d-Motor (LF26) I'm finding it quite interesting. Especially interesting when you consider the d-Motor is a flat-head design. It just doesn't compare to those flat-head engines last produced by Detroit around 1953. First, the LF26 is a short stroke engine (bore 103.6 mm/stroke 80 mm). Wild. Vastly different from my Grandfather's 1950 Dodge!

Secondly, it is very high compression (8:1) compared to the flat-heads last produced. The last Ford flat-head V-8's may have been juiced up to about 7.3:1 or so.

It took some low-speed torque to get those heavy cars moving smoothly back then; hence, a nice LONG stroke to produce a torque peak of say, 1400 rpm.

What would be MORE interesting, though would some real-world thrust testing.

[Av8r3400]

I saw this motor run at Airventure. Intriguing to say the least. I don't think I'm sold on the "flat head" idea, yet. But it did look interesting.

Lets see a few out flying and a support network established here in the 'States and we may be able to talk....

[Danzer1]

This one was also on my preliminary engine list, so I've checked into it a fair bit. Clarification of a few things already mentioned:

D-Motors site indicates a 1500 Hr TBO not 2000 and a 300 HR warranty.

The 125 Lb weight includes the oil radiator but not the cooling radiator or associated piping and mounting hardware. None the less, it still seems light, which makes me wonder if some internals have been reduced in weight which might affect longevity/reliability. I'm not willing to be the PAYing test pilot to find out.

The current price is 12,600 Euros plus 125 for crating plus shipping to you. So at today's rate 12725 Euros = $17,250 plus shipping from Belgium.

D-Motors HP & Torque curve are in metric units - DIN HP and Newton Meters torque. Factory rated at 91.7 HP @ 3000 RPM. This equals 90.5 US HP and 158.4 Ft Lb of torque at 3000 RPM. (Not very torquie - new word).

Also their site states "max" at 3000, but does not say you can run it there or if you can, for how long? They state 2800 RPM continuous. Which is 87.5 HP (US) and 164.1 Ft. Lbs of torque. Still not very torquie!

Fuel consumption is listed as 12 L/Hr (3.17 gallons per hour) at 75%. So is that 75% of rated or 75% of max continuous?

75% of 3000 = 2250 = 68.4 HP US and 159.7 Ft Lb torque
75% of 2800 = 2100 = 60.3 HP US and 150.8 Ft Lb of torque

This is a direct drive motor, so the engine rpm's are also prop rpms. In other words - you don't get any increased torque available as you would with a reduction drive/geared motor. It is what it is.

So it seems conceivable that it could be sipping fuel at those numbers. So the real question is, are those numbers high enough to get you where you want to be, when you want to be there - the way you fly?

Would be nice to see the full fuel flow data - one point is not enough to draw a line, no less a curve, so their single point is pretty useless. They had enough data to plot hp/torque curves - yet only publish a single fuel flow point - why do manufacturers do this? Every dyno I know of pulls the fuel flow numbers at the same time - so why don't they give them to us?

Anyway, this ones not for me either. But the LF39 6 cylinder that is in the works might. That one is not as far along though and I'm still not willing to be a paying test pilot for any engine manufacturer.

I touch on all this, because mostly what I hear is "rated HP" and it really doesn't matter! It is always at an unusable point in the curve and never close to where anyone is going to fly it anyway. Torque@rpm/fuel flow/prop diameter/prop pitch/LD ratio/altitude density - lots of real important variables & HP isn't one of them!

So, I'm still evaluating power plants.
Greg

[N714SM]

I have been watching the dollar get handed its lunch by the Euro slowly but surely over the last year. Not good.

D-Motor is quite the enigma from a marketing perspective. It's easy to get the impression that there is almost no interest in selling those things over here -- perplexing at best. BUT if you call or email Doc he will be happy to discuss the power plant and even provide you with some very interesting info you couldn't possibly find on the internet.

I like the idea of cooling cylinders with water. It works much better than air.

[Danzer1]

I too have been watching the dollar sink to the Euro, but because I am interested in the (still more expensive) UL 315is. Hopefully the cycle will reverse and towards the end of 2014, I'm hoping it will be much more reasonable.

As mentioned before, I threw the LF 26 out of the mix for my consideration as it simply doesn't have enough UMPF for me. However the LF 39 does and compares very closely to the 315is.

That said, I have looked further into the D-Motors and still have the following concerns (applies to either D-Motor):

Weight; I know virtually all manufacturers don't include all of the items required to operate an engine in their weights listed. Knowing that, I still can't see an operating weight near 125 pounds. Maybe for the core engine "with liquids". But this also has a radiator, oil cooler, oil reservoir, cooling reservoir, ecu and fuel pump, all mounted separate from the engine. I'd really like to see some users post actual firewall forward installed weights - my guess would be between 150 and 160.

Extended testing/reliability: There is still very little info about the LF 26 in operation and virtually none on the LF 39.

The above being important (besides the obvious reasons) because - after looking past the cool flat head design - it finally dawned on me that the INTAKE IS MOUNTED ON THE BOTTOM of the engine!

Has anyone ever seen a bottom mounted intake? If so, I'd like to know how well and how long they worked. Anyway, I've never seen one and so (being an ex engineer) it got me wondering - what could go wrong there?

Hmm:

It's next to and above the exhaust and muffler - MIGHT add some heat to the intake air - never good for efficient combustion. Maybe negligible though.

D-Motor says and I quote "When a valve of a sidevalve engine is not closing, you continue flying with less power and there won't be expensive repair cost"

What happens when the rings, valve seals etc. break in and over time wear and allow oil seepage? Where does that oil go? Where does the oil and/or water go if a gasket fails (head or intake)? Or head or block crack? In a conventional top mounted intake - it mixes fluids till it overheats and/or drips off outside the case and keeps running until there is not enough fluid left and/or it overheats and then it fails. IF water and/or oil can get into the bottom mounted intake (likely as there is a direct path) - I'd bet it would stop running pretty quickly.

So, I'd really need to see an extensive amount of time built on either of these engines before investing in one.

Just my 2 cents!
Greg

[Av8r3400]

The above being important (besides the obvious reasons) because - after looking past the cool flat head design - it finally dawned on me that the INTAKE IS MOUNTED ON THE BOTTOM of the engine!

Has anyone ever seen a bottom mounted intake? If so, I'd like to know how well and how long they worked. Anyway, I've never seen one and so (being an ex engineer) it got me wondering - what could go wrong there?

It's next to and above the exhaust and muffler - MIGHT add some heat to the intake air - never good for efficient combustion. Maybe negligible though.

Most certified reciprocating engines use an updraft induction system with the intake and exhaust below the engine. Lycoming engines even route the intake runners through the oil sump, with the carburetor bolted directly to the sump, to heat the intake charge lessening the likelihood of induction icing.



I took a long look at the D-motor at Airventure this year. It is a very interesting motor, to say the least, but I also am very skeptical on the efficiency of a flat head design in regard to combustion. Flow and swirl are major considerations on a reciprocating engine. If flat head motors weren't so inefficient, they would still be in use in the automotive industry.

[Danzer1]

Guess I should have been clearer - it's the bottom mounted intake without an oil sump that concerns me. All of the certified ones had an oil sump to collect the gravity flowing oil. This doesn't, it is a remote mounted tank firewall mounted higher than the engine, so the intake system is the only place for it to go if there was a failure/leak/seepage.