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D-Motor Company

D-Motor Company, Belgium

Late 2010 D-Motor Company is formed in Belgium to produce and market an engine which has been researched and developed over a period of many years. Its designs are based on existing and well proven technology. The four stroke side valve (flat head) boxer engine was developed using the very latest technology including multi-point fuel injection, electronic ignition and liquid cooling to give a maximum continuous power of almost 89 bhp.

The company uses the latest CNC technology to make sure that the parts are designed and built to the highest standards in aviation. Many bench runs and flight hours have been performed to make sure that reliability and durability of the engine is what can be expected from an aircraft engine.

At the moment (2014) the company has a four cylinder model flying and a six cylinder is almost ready for testing and flying. In 2016 some installations with the LF39 engine were nearing completion.

Engine Design

There are two products at the moment, the basic four cylinder engine, which is also available in a helicopter version with and integrated flywheel, clutch and freewheel. Their latest development is a higher powered version with six cylinders, suitable for the larger ultralights, LSA and experimental aircraft on the market today.

D-Motor LF-26

The engines are water cooled (no shock cooling), direct drive (no gearbox), fuel injected (no carburetor icing), and this is the interesting part: it is a flat head design where the valves are on the side of the engine and not on top. The other feature is that the bore stroke ratio is 1.4 to 1.

D-Motor decided to use large bore pistons with nikasil coated cylinders running at low RPMs with a high cubic capacity resulting in a high torque engine with less moving parts than a comparable high revving Rotax engine. These design decisions will lead to a lightweight, long service life engine.

Like in a Rotax this design uses a liquid cooling system with radiators (handy for safe cabin heat in the winter) but due to the simpler flat head there is no total extra weight involved. The ignition system is ECU controlled with dual spark plugs per cylinder. The lubricating oil is contained in a separate sump, as it is with a Rotax.

With side valves (although volumetric efficiency is a bit less compared to overhead valve engines): should one of these break and stop moving there will be no piston damage, but power will be available at a reduced level so you can land under control. Overhead valve engines will usually damage a piston (and more) due to the broken or stuck valve, with total engine failure and you may expect expensive engine / aircraft repairs to be the result.

LF 26

D-Motor LF-26

Below an overview of the four cylinder LF26 (2690 cm3) engine and its specifications, do note the low weight.

Technical Specifications

ModelLF26 4 cylinders
EngineFour cylinders, four stroke, liquid cooled
Displacement2690 cm3
Stroke80 mm
Compression ratio8:1
Maximum power91.8 hp (67.5 kW) at 3000 RPM
Maximum continuous power88.8 hp (65.3 kW) at 2800 RPM
Fuel type95 / 98 octane mogas or avgas
Fuel consumption12 liter at 75% power
Maximum torque220 Nm at 2500 RPM
IntakeMulti-point sequential fuel injection
Alternator25 Amp integrated
Electric starter1.1 kW integrated
IgnitionECU Dual
Installed weight58 kg (liquids included, battery not included)

A nice installation in a Jabiru as shown in this YouTube video from: D-Motor Australia.

LF 39

D-Motor LF-39

For the six cylinder LF39 (3993 cm3) engine the specifications are in the table below:

Technical Specifications

ModelLF39 6 cylinders
EngineSix cylinders, four stroke, liquid cooled
Displacement3993 cm3
Stroke79 mm
Compression ratio8:1
Maximum power130 hp (97 kW) at 3000 RPM
Maximum continuous power125 hp (93.3 kW) at 2800 RPM
Fuel type95 / 98 octane mogas or avgas
Fuel consumption18 liter at 75% power
Maximum torque300 Nm at 2500 RPM
IntakeMulti-point sequential fuel injection
Alternator25 Amp integrated
Electric starter1.1 kW integrated
IgnitionECU Dual
Installed weight78 kg

As this engine is still under development these numbers could change anytime, it would be a good idea to keep an eye on the website of D-motor Company.

A running version can be seen in the next YouTube video: Aero-TV: 6 Cylinder D-Motor.

Written by EAI.

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