BMW-Bramo 323

Manufacturer: BMW
Developed: 1936
Type: 9-cylinder supercharged air-cooled radial engine
Number Built: ~5,500

Bore: 154 mm (6.06 in)
Stroke: 160 mm (6.30 in)
Displacement: 26.82 litres (1,636.8 cubic inches)
Length: 1,420 mm (55.9 in)
Diameter: 1,388 mm (54.6 in)
Dry weight: 550 kg (1,210 lb)

Valvetrain: Pushrod-actuated overhead valve
Supercharger: Gear-driven
Fuel system: Fuel injection
Fuel type: 87 Octane petrol
Cooling system: Air-cooled

Power output:
– 670 kW (900 PS) at 2,500 rpm at sea level for take-off
– 745 kW (1,000 PS) at 3,100 m (10,200 ft)
Specific power: 27.8 kW/L (0.61 hp/in�)
Compression ratio: 6.4:1
Specific fuel consumption: 0.348 kg/(kW�h) (0.572 lb/(hp�h))
Power-to-weight ratio: 1.36 kW/kg (0.83 hp/lb)

Design & Structure:
FUEL INJECTION – Maihak duplex feed pump draws fuel from supply tank through lines and combined cocks and filters, the deliveries combining to pass through de-aerator and thence to Bosch injection pump. This nine-cylinder pump is similar to that fitted to BMW 132 engine. Quantity-Control racks moved by oil servo-motor controlled by boost pressure. Changes in exhaust back pressure and (unlike BMW) in boost air temperature have no controlling effect. Metered fuel fed through soft iron pipes to Bosch injection valves in &ont of cylinder-heads. Askania automatic boost-pressure control unit as used on BMW 132 engine.

LUBRICATION - Scavenge and pressure pumps mounted as single unit on auxiliary gear box. Pressure oil passes into ducts in wall of auxiliary gear box and to edge-type filter provided with external cleaning handle and thence through non-return valve and cored passage in lower part of supercharger casing to all components. Drainage from all parts of engine to magnesium-alloy sump on underside of crankcase, scavenge oil being drawn through wire gauze filter in bottom of sump.

IGNITION - Dual Bosch magneto mounted on upper part of auxiliary gear box and provided with draught of cooling air through a duct. Two Siemens plugs per cylinder. Conventional ignition harness.

AUXILIARY DRIVES - Auxiliary gear box is a magnesium-alloy casting mounted on rear of supercharger casing. Drive taken from gear wheel formed on supercharger spring drive to gear of same size on layshaft, after end of which is machined with claws for inertia starter. Train of gears drive magneto, tachometer, oil pumps, vacuum pump, petrol pump, injection pump and generator.

COWLING AND BAFFLES - Three baffles of aluminum-alloy sheet to each cylinder, two side pieces and a head-piece, all closely fitting to the fin tips. Side pieces extend from push-rod tubes in front to within a few inches of center line at back of cylinders. Head piece fixed to rocker boxes and extends outwards to ring running round engine and itself in contact with external cowling. Inter-cylinder spaces filled by flat pieces extending to ring and through these are air intakes for magneto cooling, breather (forward side of supercharger impeller) port and starboard air heaters, generator cooling and breather from sump. There is no internal cowling behind engine except a deflector for warm air intake of supercharger. Large diameter nose cowling of aerofoil section attached by struts to reduction gear casing and crankcase. Remainder of cowling, extending to rear of oil cooler, parallel and hinged at top to give access to engine. No means of controlling air flow provided.

MOUNTING - Lugs on supercharger casing pick up nine points on mounting ring, through rubber bushes and bolts, which forms part of triangulated welded steel-tube structure terminating in four spherical joints for attachment to the airframe. A twin steel wire cable is wound round various parts of the mounting and attached by links to brackets high up on the airframe to prevent the engine falling out should the bearer break.

The Bramo 323 Fafnir was a 9-cylinder radial aircraft engine of the World War II era. Based heavily on Siemens/Bramo's earlier experience producing the Bristol Jupiter under license, the engine was not particularly modern and saw limited use.

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