|Type||6-cyl. In-line, water-cooled, diesel, piston engine.|
|Designed by||Louis Coatalen|
|Number built||prototypes only|
|Developed from||Sunbeam Dyak|
Design and development
Louis Coatalen, Sunbeam engine designer, started work on a diesel powered aero-engine, that would be suitable for use in airships, in 1928. Using his experience with both aero-engines and auto-mobile diesel engines, the result, given the company designation P.1, was based on the Dyak. Given the name Pathan, a prototype engine was displayed at the 1929 Olympia Aero Show, but attracted no orders.
Using the same bore and stroke of the Dyak (120mm x 130mm - 4.72in x 5.12in ), the Pathan was a water-cooled six-cylinder in-line diesel engine with a cubic capacity of 8.8l (537cu in). Rated to give 100hp (74.6kW) @ 1,500rpm the engine was fitted with a new type of fuel injection system allowing cold starts without other assistance.
Coatalen continued the development of Diesel engines after he left Sunbeam and returned to France, developing the Coatalen V-12 Diesel engine with limited success, due to the German invasion of 1940 halting further work.
Data from 
- Type: 6-cylinder, inline diesel engine
- Bore: 4.72 in (120 mm)
- Stroke: 5.12 in (130 mm)
- Displacement: 537 cu in (8.8l)
- Fuel system: Direct fuel injection
- Fuel type: Diesel oil
- Oil system: Dry sump, pressure fed
- Cooling system: Liquid-cooled
- Power output: 100hp at 1,500 rpm
- Specific fuel consumption: 0.169l/kW/hr (0.4 pints/hp/hr)
- Oil consumption: 0.0127l/kW/hr (0.03 pints/hp/hr)
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