D-Motor

[geoffreywh]

D-Motor news. There is an update on the D-Motor website (at last) explaining their absence from the news lately. I really like the D-Motor for its simplicity and design. They have enlarged the 80hp motor (longer stroke) so it now puts out almost 100 at 3000rpm. The six (the reason for absence of progress) is now almost ready too having 135hp. They appear to have the flattest torque curve I've ever seen outside steam engines...I'm not ready to buy one yet....................but maybe not too far away...........Geoff

 

 

[Old Koreelah]

D-Motor news. There is an update on the D-Motor website (at last) explaining their absence from the news lately. I really like the D-Motor for its simplicity and design. They have enlarged the 80hp motor (longer stroke) so it now puts out almost 100 at 3000rpm. The six (the reason for absence of progress) is now almost ready too having 135hp. They appear to have the flattest torque curve I've ever seen outside steam engines...I'm not ready to buy one yet....................but maybe not too far away...........Geoff

Thanks for the update, Geoff. I like this engine.

Recent advances in engine management technology may give other previously discarded designs a new lease on life.

 

 

[greg stephens]

And it fits directly on a jabiru mounting, so don't need to reinvent the wheel.

 

 

[ducksrus]

Just viewed the d-motor video at www.D-MotorUSA.com also info at www.d-motor.eu This looks great ! 2700 cc boxer 4 cyl flat head side valve, fully water cooled, injected, direct drive 95 hp with a Jabiru mount, looks very simple and compact. I think this engine is starting to gain momentum, might be a good one to keep an eye on. 6 cyl on the way also.

 

 

[bexrbetter]

One thing that lets a Flatty down is large chamber surface area allowing large amounts of heat to escape rather than pushing your pistons down the bore and turning your crank with full efficiency.

 

This will lead to higher fuel consumption which may or may not be offset by the more aerodynamic smaller frontal area it can offer depending on people taking advantage of that or not.

 

I'm not a believer in going backwards so I'll put up rather than shutup

 

 

[xair1159]

I recently visited the D-Motor factory in Belgium and the huge investment they have made in CNC machines, dyno, flow bench and other plant shows these guys are serious about making a good product.

 

The side valve/flathead may be old style, but its high, flat torque curve is ideal for a direct drive, low rpm aircraft engine. The original flathead complaint of poor breathing isn't really a problem at 3000 rpm.

 

They have spent several years developing the engine and it has some very clever and subtle design tweaks - many modern techniques like flow visualisation weren't around when the original design went out of fashion.

 

I fly an aircraft fitted with a 2200 Jabiru and have also flown the identical airframe with the D-Motor. My Jab is a mid range hyd tappet version with a claimed 80hp and has been reliable but sadly lacking in power, so there is a huge jump in performance with the D-Motor thanks to a demonstrated 91+ hp. Comparing the published Jabiru curves with a D-Motor dyno printout shows roughly 10hp more at all revs from 2200 to 3000.

 

I have a feeling that in real life with the hyd tappet engines this is probably nearer to 15hp more.

 

My Jab 2200 installation weighed 68kg (I weighed all the major lumps) the D-Motor is at least 10kg less at 56-57 kg, both wet and ready to fly.

 

Ref the comments about efficiency and fuel burn, the D-Motor is actually better than the Jabiru thanks to the full EFIand the fact you are not running a carby excessively rich to try and cool the valves. If a valve fails or sticks in the Jabiru (not uncommon) one way or another it meets the piston, the engine is toast and you have a problem. Should the same happen in a flathead you just continue to run on 3 cylinders which should get you safely on the ground.

 

The first 25 engines are being delivered now. Yes, it is early days and hours have to be accumulated to demonstrate long term reliabilty, but I am impressed with the engine. Might be a s/h Jab 2200 for sale shortly.

 

 

[cooperplace]

I recently visited the D-Motor factory in Belgium and the huge investment they have made in CNC machines, dyno, flow bench and other plant shows these guys are serious about making a good product.The side valve/flathead may be old style, but its high, flat torque curve is ideal for a direct drive, low rpm aircraft engine. The original flathead complaint of poor breathing isn't really a problem at 3000 rpm.

They have spent several years developing the engine and it has some very clever and subtle design tweaks - many modern techniques like flow visualisation weren't around when the original design went out of fashion.

 

I fly an aircraft fitted with a 2200 Jabiru and have also flown the identical airframe with the D-Motor. My Jab is a mid range hyd tappet version with a claimed 80hp and has been reliable but sadly lacking in power, so there is a huge jump in performance with the D-Motor thanks to a demonstrated 91+ hp. Comparing the published Jabiru curves with a D-Motor dyno printout shows roughly 10hp more at all revs from 2200 to 3000.

 

I have a feeling that in real life with the hyd tappet engines this is probably nearer to 15hp more.

 

My Jab 2200 installation weighed 68kg (I weighed all the major lumps) the D-Motor is at least 10kg less at 56-57 kg, both wet and ready to fly.

 

Ref the comments about efficiency and fuel burn, the D-Motor is actually better than the Jabiru thanks to the full EFIand the fact you are not running a carby excessively rich to try and cool the valves. If a valve fails or sticks in the Jabiru (not uncommon) one way or another it meets the piston, the engine is toast and you have a problem. Should the same happen in a flathead you just continue to run on 3 cylinders which should get you safely on the ground.

 

The first 25 engines are being delivered now. Yes, it is early days and hours have to be accumulated to demonstrate long term reliabilty, but I am impressed with the engine. Might be a s/h Jab 2200 for sale shortly.

very interesting, thank you. The side valve certainly has advantages, and the ability to keep running on 3 is intriguing. How long could it safely keep this up? I would be grateful if you could comment on: (i) actual improvement in fuel economy, as a number, and (ii) all-up cost difference vs Jab 2200

 

 

[cooperplace]

I recently visited the D-Motor factory in Belgium and the huge investment they have made in CNC machines, dyno, flow bench and other plant shows these guys are serious about making a good product.The side valve/flathead may be old style, but its high, flat torque curve is ideal for a direct drive, low rpm aircraft engine. The original flathead complaint of poor breathing isn't really a problem at 3000 rpm.

They have spent several years developing the engine and it has some very clever and subtle design tweaks - many modern techniques like flow visualisation weren't around when the original design went out of fashion.

 

I fly an aircraft fitted with a 2200 Jabiru and have also flown the identical airframe with the D-Motor. My Jab is a mid range hyd tappet version with a claimed 80hp and has been reliable but sadly lacking in power, so there is a huge jump in performance with the D-Motor thanks to a demonstrated 91+ hp. Comparing the published Jabiru curves with a D-Motor dyno printout shows roughly 10hp more at all revs from 2200 to 3000.

 

I have a feeling that in real life with the hyd tappet engines this is probably nearer to 15hp more.

 

My Jab 2200 installation weighed 68kg (I weighed all the major lumps) the D-Motor is at least 10kg less at 56-57 kg, both wet and ready to fly.

 

Ref the comments about efficiency and fuel burn, the D-Motor is actually better than the Jabiru thanks to the full EFIand the fact you are not running a carby excessively rich to try and cool the valves. If a valve fails or sticks in the Jabiru (not uncommon) one way or another it meets the piston, the engine is toast and you have a problem. Should the same happen in a flathead you just continue to run on 3 cylinders which should get you safely on the ground.

 

The first 25 engines are being delivered now. Yes, it is early days and hours have to be accumulated to demonstrate long term reliabilty, but I am impressed with the engine. Might be a s/h Jab 2200 for sale shortly.

also, how noisy is it? thanks

 

 

[facthunter]

It is old configuration and has some disadvantages in theory. They were originally considered more reliable as a valve stem or collets could come out or spring break, and all the valve does is rise till it contacts the cylinder head, rather than drop into the bore and ruin everything. Bore distortion due to the positioning of the exhaust port, is one of it's main faults plus an inherent lack of efficiency due to the large surface area of the combustion chamber allowing heat to be lost that could have added torque.

 

The motor is more compact and lighter and cheaper to produce. The larger cylinder head gasket area and distortion are likely to cause gasket failure. We will see how they go. If it is well engineered it may find a niche. Most higher performance side valves would be liquid cooled as they are hard to cool evenly by air. the exhaust port to cylinder area being the most difficult. Nev

 

 

[bexrbetter]

The side valve/flathead may be old style, but its high, flat torque curve is ideal for a direct drive, low rpm aircraft engine. The original flathead complaint of poor breathing isn't really a problem at 3000 rpm.

.

It is old and it has problems, it's advanatages are size and weight (very tempting for this application of course), everything else is technically lower and any overhead valve engine can make a better torque curve hands down at any rpm point.

 

The poor breathing is an issue at any rpm beacause swirl and surface wetting can not be controlled therefore complete atomisation can not be had simply wasting a lot of fuel each burn. Dirct Injection would seriously help but this engine is port fed, certainly helps a little with atomisation but no cigar.

 

Iit has some very clever and subtle design tweaks - many modern techniques like flow visualisation weren't around when the original design went out of fashion.

Really? Sorry I can't see them, the valves appear to be equi-centered and the spark plugs are positioned poorly which annoys the hell out of me as they knew they had to have 2 for aviation so why not take advantage of that. I don't see anything special about the heads, no flame troughs, no swirl inducers etc, so I simply don't believe there is any modern takes on it - ceramic heads would have impressed me though.

 

Ref the comments about efficiency and fuel burn, the D-Motor is actually better than the Jabiru thanks to the full EFIand the fact you are not running a carby excessively rich to try and cool the valves.

Well lets compare a Rotax with EFI then shall we rather than a carby Jabiru? What's the concentration on comparing it to a Jabiru about?

 

Cooling exhaust valves and seats on a Flatty is a huge issue, you are just plain wrong to make that comparison to any OHV engine. Localised cylinder distortion and valve burning/seat distortion in Flatty's is a key reason as to why OHV engines came to be a prefered choice. How they have designed their exhaust valve seat area will be crucial and may make or break them.

 

If a valve fails or sticks in the Jabiru (not uncommon) one way or another it meets the piston, the engine is toast and you have a problem.

I'm not a Jabiru fan and am aware of some of their issues, but do you have statistics that valve siezure has caused piston failure leading to utter and complete engine failure on the Jabs or other? From what I have learnt and seen so far Jabiru's problems seem to be constant, costly and annoying but not killers.

 

If a valve fails or sticks in the Jabiru (not uncommon) one way or another it meets the piston, the engine is toast and you have a problem. Should the same happen in a flathead you just continue to run on 3 cylinders which should get you safely on the ground.

and all the valve does is rise till it contacts the cylinder head, rather than drop into the bore and ruin everything.

The side valve certainly has advantages, and the ability to keep running on 3 is intriguing.

These are blanket statements rather than factual. I have seen many a OHV engine drop a valve and continue running on with bits or the actual valve head imbedded in the combustion chamber or piston (plenty of evidence on the net if you look but of course the more dramatic failures are more common for their shock value) as I have seen them also break a piston and come to a very smoky stop (but still running). Anyone who thinks parts of a Flatty's valve head or stem can't get to the cylinder is simply wrong, safer yes for such things as spring breakage, but impossible? - absolutely not, so don't carry that sense of false security around.

 

Anyway, not against it, just putting up technical arguments and corrections about Flattys (hey it's Sunday morning!) and, as mentioned, they are disadvantaged but the lower frontal area and lower weight advantages may make up the differences and it may actually put it ahead of it's competition if done properly.

 

Does anyone have a price on these engines? Might all be a moot point if they want the world for them.

 

 

[damkia]

According to their site about 19000 Euro (AUD$23500-24000) plus freight etc.

 

Still needs radiators and other cooling requirements

 

 

[Downunder]

Thanks for your post xair1159 and assessment of the engine. At least you have BEEN TO THE FACTORY and FLOWN BEHIND ONE...........

 

As you own a Jabiru engine is would make sense that you would compare the D-motor to this.

 

 

[geoffreywh]

Too bloody right. Downunder........All the speculation in the world on the merits and failings mean nothing when compared to the practical demonstration of flying behind one. The Jab DOES HAVE a bad problem with early retirement. The D-Motor DOES HAVE an impressive profile. Time will tell all. I like the design, so there.

 

 

[facthunter]

I though most contributionshere did deal with facts around the side valve design. Some of us have a large experience with them. This is somewhat hard to get these days for obvious reasons. Whether someone "likes' or "dislikes " something is a matter of personal belief. The engine deserves to be evaluated and will prove itself or otherwise with time. The first american 'flat" engines were sidevalve. They are extremely compact and potentially a little lighter and essentially simpler. Valve guide wear should be less of a problem because the follower pushes straight on the valve stem in line with it. Nev

 

 

[bexrbetter]

Still needs radiators and other cooling requirements

Thanks Damkia.

 

And when servicing or your TBO comes up you will be at their mercy for parts, good luck when the nikosil lining need replacing too - that light weight comes at a proven financial risk. http://kustom-kraft.com/NEWNIKASIL.html

 

According to their site about 19000 Euro (AUD$23500-24000) plus freight etc.

What is with that price, this is supposed to be a simpler and easier engine to produce using less parts, so why isn't it cheaper? Don't understand it myself, why not base your design around proven commercially available parts such as a Lancia Gamma or Subaru 2.5 crank and rods amongst other choices and just whip up your own engine cases to suit requirements.

 

.All the speculation in the world on the merits and failings .

Ain't speculation Geoff, Flatheads were once the most common of mass produced engines and at one point made up 95% of all engines in the world, notice any around these days?

 

At least you have BEEN TO THE FACTORY and FLOWN BEHIND ONE............

10 minutes does not maketh an engine.

 

 

[Downunder]

10 minutes does not maketh an engine.

But it's an opinion and judgement a heck of a lot more substantiated than anyone else on this thread....

 

 

[bexrbetter]

But it's an opinion and judgement a heck of a lot more substantiated than anyone else on this thread....

Finished here except to mention that everything has it's place in the laws of physics and those laws can not be broken or bent by opinions.

 

Also read as "Don't shoot the messenger"!

 

 

[damkia]

???http://www.d-motor.eu/nl/price-37.htm

12600€ Roughly $15500 +Radiator ++Packing crate and Freight

Sorry about that, I was drooling over the 6 cylinder...

 

 

[damkia]

Forgiven...and Ditto... but at the price is about the same as the Rotax injected

but What IS needed is a around 100hp+ Diesel....

 

Can't imagine in a region where they relish in their diesel cars.. why there are not more effective diesel aircraft motors coming out of Europe

I agree...

There is a very nice little Mitsubishi turbodiesel (4N13) that fits into the ASX in some markets that would make a very good start. Alloy block, offset crankshaft (vibration and friction reduction) and a nice flat torque curve

 

http://www.mitsubishi-motors.com/en/spirit/technology/library/diesel.html

 

 

[xair1159]

Ain't it great to start a good discussion!

 

Some interesting and apparently well informed comments from a couple of people though.

 

To try and answer some of the points in no particular order:-

 

My "10 minute flight" was 2 hours as P1 on the production version and another 3 or 4 hours as P2 on a couple of previous versions.

 

They did try various head and piston configurations, I was shown a number of them in the scrap bin.

 

Different plug and valve positions were tried, again some samples were in the bin. I believe they found moving the plugs even a small amount made a significant difference.

 

Different types and makes of plugs were tried before settling on one used by Mercedes which gave a small but repeatable hp gain.

 

Exhaust valves are sodium filled to help with heat removal, inlets are usual style.

 

Fuel burn - I have an MGL Xtreme with fuel flow and cruise my Jab 2200 at 2500-2600 which gives me a genuine 80kts. Fuel burn is 13L/hr at 2500 up to 14 L/hr at 2600. I will try and get hold of similar accurate figures for the D-Motor, but from my flight I would guess at 11-12 L/hr for the same cruise speed.

 

One thing I did notice was that a well used engine that had been stripped for checking had remarkably clean heads and pistons. My Jab required a head job at 350 hrs due to rough running and failed hyd tappets and it was well coked up with burnt oil and from running rich on the factory supplied jetting. Perhaps EFI and valve stem seals have something to do with this?.

 

There are some tweaks which to my knowledge were never used on old flat head engines. (Showing my age, my first wreck of a car was a flattie).

 

Why not use Subaru type auto conversions - most are heavy. Having said that, the Viking looks interesting, but it is still heavy, which is a problem with a 450kg limit, plus possible CG problems.

 

Cost of spares / Nikasil - not knocking them, but as a Jabiru user, will these be any different to constant changes being made, many of which are not retro fit? Thin fin heads, different size and location for through bolts, hyd tappets, roller tappets, various cams etc. Any small volume manufacturer will have the same problem. Time will tell.

 

With the supplied silencer it is not loud (we have to pass noise tests here for certification) but the usual comment is that it does sound more like a "proper" a/c engine.

 

I would imagine D-Motor have ended up with the best compromise between power, fuel, heat, efficiency, cost etc. etc. Aren't most designs of almost anything a compromise unless you have unlimited budgets and time? No one in their right mind is going to knowingly sell a poor design.

 

 

[bexrbetter]

Hi Xiar,

 

Nice post, thanks for taking the time for you're report.

 

That they tried different spark plug positions ending up with one generally where it should be yet the other exactly where it should not be and based on them being symetrical I find a litle odd.

 

Yes EFI or rather the correct fuel metering, has the ability to keep things much cleaner and increase ring and bore life through less bore-washing from rich mixtures and of course less carbon or soot build up.

 

Genuinely interested in the "tweaks" twice mentioned.

 

No one in their right mind is going to knowingly sell a poor design.

Sadly, historically far from the truth of the matter.

 

 

[facthunter]

With a carb equipped jabiru, the leanest cylinder is the one(s) that cause the others to use an excessively rich mixture and more carbon build up. More precise fuel metering would aid most engines. Individual cylinder injection is ideal. It's close to impossible to get even fuel mixture otherwise, but some do it better than Jabiru even though they have spent a lot of effort on it.

 

Best location of the plugs in a flathead motor are often found by experimentation rather than the theoretical best. The hottest parts of the combustion chamber should be burned first, in theory. Nev

 

 

[bexrbetter]

The hottest parts of the combustion chamber should be burned first, in theory. Nev

Indeed, so why is the other one disturbing flow, getting wetted and in the coldest spot?

 

 

[facthunter]

They should be close together if the timing won't be miles out with single mag ops. Putting the plug above the exhaust valve doesn't promote the smoothest running for some reason. This could be associated with mixture distribution and be less of a problem with injection. It's quite likely that the plugs should be a different heat range also because of their placement. In most aero engines they are wide apart in the combustion chamber , probably to reduce the total time to burn all the charge and thereby use less advance on the timing. Nev

 

 

[Bandit12]

One day Nev, you really have to share your aviation history with us all in a more complete sense. It really deserves it's own thread.