The D-Motor LF26 is a lightweight liquid cooled side-valve four-stroke flat four, 2.7L petrol aircraft engine, produced by D-Motor in Deerlijk, Belgium.
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Design and development
This direct-drive aero-engine is unusual in two respects: it is very oversquare with a bore:stroke ratio of 1.295:1, and it has a side-valve valvetrain. The designer determined that since maximum continuous power output (65.3kW) was to be developed at only 2800 rpm, the extra weight and complexity of overhead valves would be superfluous. The resulting engine is compact and lightweight, with a dry weight of 58 kg (128 lb), and a maximum power-to-weight ratio of 1.09 kW/kg (wet; coolant fluids weigh 5 kg (11 lb)).The engine uses fuel injection, so carburetor heat is unnecessary. Lubrication is by dry sump, with an external oil tank. Dual ignition is used, each cylinder having twin spark plugs sited between the valves and the piston crowns.
Unlike an engine which uses ohv to be capable of high revs, a feature of the slow-revving side-valve arrangement is that the engine does not suffer high frictional losses, so the power curve is virtually linear up to 3100rpm. An inherent disadvantage of the side-valve design is the relatively inefficient shape of the combustion chamber; but there remains potential for squish to promote turbulence of the fuel/air mix, and the low rpm means that the flame front is able to ignite all the fuel in each power stroke.
In its page "Concept and advantages of the D-motor", the company claims:
Variants
With the aid of funding from the Belgian government, D-Motor has developed a derivative 4L flat-six engine,the D-Motor LF39, and this motor is claimed to produce 125 hp (93 kW) and to have dry weight of 78 kg (172 lb).
Applications
Specifications
Reference: D-Motor