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Isotta Fraschini Delta

Isotta Fraschini Delta was a 12-cylinder inverted-V aircraft engine that is a fairly rare example of a large air-cooled inline engine. these engines tend to have cooling problems with the rearmost cylinders. It produced about 750 hp in common versions, although others were rated up to 900 hp. The Delta was not widely used, although it could be found on a number of production aircraft and some advanced prototypes.

The engine included a number of otherwise advanced features. For instance, the valves were powered by dual overhead cams driven by power shafts at the rear of the engine. Exhaust ports were arranged to exit toward the middle of the engine, one cylinder bank being the mirror of the other, allowing the piping to be ganged below the engine nacelle.

Manufacturer: Isotta Fraschini
First Run: 1927
Type: 12-cylinder air-cooled 60 degree inverted vee
Bore: 132 mm (5.197 in)
Stroke: 160/165 mm (6.299/6.496 in), with main and articulated rod
Displacement: 26.685 Litres (1,628.44 in³)
Length: 2000 mm (78.8 in.)
Width: 840 mm (33.07 in.)
Height: 883 mm (34.76 in.)
Dry weight: 510 kg (1,111 lb)
Components:
– Valvetrain: 2 Poppet valves per cylinder, sodium cooled exhaust valves, double overhead camshafts.
– Supercharger: single stage single speed centrifugal type supercharger, gear ratio 9.8:1
– Fuel system: 4*Isotta Fraschini downdraft carburetors
– Fuel type: 80/87 octane petrol (aviation gasoline)
– Oil system: dry sump, 2 scavenging, 1 pressure pump
– Cooling system: Air-cooled

Performance:
Power output:
– Rated power: 750hp at 2,600 rpm at 4,000 meters
– Take off power: 770 hp at 2,600 rpm
Reduction gear ratio 0.64:1
Specific power: 0.47 hp/in³ (21.5 kW/L)
Compression ratio: 6.4:1
Specific fuel consumption: 270 grams/hp*hour maximum, 250 grams/hp*hour cruise (70%)
Power-to-weight ratio: 1.485 hp/kg (0.67 hp/lb)

Variants:
The Italian engine designation system includes a suffix indicating major components or attributes. The most common were R for Riduttore - reduction gear and C for Compressore - compressor/supercharger, followed by a number indicating the rated altitude in hundreds of metres, two speed superchargers were indicated by a double figure such as 10/34.

– Isotta Fraschini Delta R.C.21/60
– Isotta Fraschini Delta R.C.35
– Isotta Fraschini Delta R.C.35 IS
– Isotta Fraschini Delta III R.C.40
– Isotta Fraschini Delta IV R.C.17/50

Applications:
– Ambrosini SAI.107
– Ambrosini SAI.207 prototype
– Ambrosini SAI.403 prototype
– CANT Z.515
– Caproni Ca.313
 – Caproni Ca.314
– Caproni Ca.331
– Caudron C.714 (C.760) prototype
– Henschel Hs 129 prototype
– Reggiane Re.2001 prototype
Sources:
Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989.
Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1989.
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