D-Motor LF26

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D-Motor LF26
Type Piston aero engine
National origin Belgium
Manufacturer D-Motor
Unit cost US $18,500 (2015)[1]
Developed into D-Motor LF39

The D-Motor LF26 is a lightweight liquid cooled, four-stroke, flat four, 2.7 litre petrol aircraft engine, produced by D-Motor in Deerlijk, Belgium.[2]

Design and development[edit]

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 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),[3] with a power-to-weight ratio of 1.46 kW/kg. Coolant fluids weigh 5 kg (11 lb).[4] 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 ohc 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 completely linear up to 3100rpm.[5] 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 ignite all the fuel in each power stroke.[6][7]


With the aid of funding from the Belgian government,[8] D-Motor has developed a derivative 4 litre flat-six engine,the D-Motor LF39, and this motor is claimed to produce 125 hp (93 kW) and to have dry weight of 74 kg (163 lb).[9]



Reference: D-Motor[3]

General characteristics

  • Type: horizontally opposed flat four
  • Bore: 103.6mm ( 4.1 in)
  • Stroke: 80 mm (2.91 in)
  • Displacement: 2690 cm³
  • Length: 611 mm
  • Width: 533 mm
  • Height: 382 mm
  • Dry weight: 58 kg with exhaust, radiator & external oil tank



See also[edit]

Comparable engines
Related lists


  1. ^ "Belgium firm offers Light Sport engine". AOPA Pilot: 40. March 2015. 
  2. ^ a b c "Kapelstraat 198 8540 Deerlijk - Recent information". D-motor1.vpweb.be. Retrieved 2012-08-14. 
  3. ^ a b "LF26 specifications". D-motor. Retrieved 26 June 2012. 
  4. ^ http://www.d-motor.eu/nl/specifications-38.htm
  5. ^ D-motor performance graph
  6. ^ http://myweb.tiscali.co.uk/speedex/index_files/Page2476.htm
  7. ^ http://www.secondchancegarage.com/public/585.cfm
  8. ^ "Kapelstraat 198 8540 Deerlijk - News". D-motor1.vpweb.be. Retrieved 2012-05-10. 
  9. ^ D-Motor publicity specification sheet, August 2014
  10. ^ D-Motor (n.d.). "X-air test plane". Retrieved 2 August 2011. 

External links[edit]