Isotta Fraschini Asso XI

The Asso XI was a family of water-cooled, supercharged V12 piston aeroengines produced in the 1930s by Italian manufacturer Isotta Fraschini, and fitted on a number of aircraft types built by CANT, Caproni and others.

Design and development
Isotta Fraschini produced a long series of engines with the name Asso (Ace, in English). The Asso XI R.C. was an upright, liquid-cooled V-12 engine with maximum power output in the range 670 - 725 kW depending on the degree of supercharging. There were two variants, differing only in their supercharger speed: the R.C.40 ran at a little over 10 times the crankshaft speed and enabled the engine to maintain a rated power of 623 kW to an altitude of 4000 m whereas the R.2C.15 held 655 kW to 1500 m with a supercharger gearing of 7.

All variants of the R.C.40 had much in common with construction of the earlier Asso 750 R.C., though they had two, rather than three, banks of 6 cylinders and 4 rather than 2 valves per cylinder. Cylinder barrels were machined from carbon steel with flat-topped heads and valve seats. Each barrel had a separate sheet steel water jacket. Cast aluminium head blocks were bolted to each of the two banks of 6 cylinders, providing valve ports, guides, coolant passages and camshaft supports. The pistons were also aluminium castings. The crankshaft was a 6-throw design with 8 plain bearings and a double row ball thrust bearing between the front two. The connecting rods had bronze bush little ends and white metal big ends. The crankcase was cast in two parts, the upper one with the housings for the crankshaft bearings.

Variants

 * Asso XI R:(R - Riduttore - reduction gear)
 * Asso XI R.C.:(C - Compressore - supercharged)
 * Asso XI R.C.15 :Supercharger speed 75/7 times crankshaft; rated power at 1500 m.
 * Asso XI R.2C.15:(2C - second supercharger gearing) Supercharger speed 7 times crankshaft; rated power at 1500 m.
 * Asso XI R.2C.16:(2C - second supercharger gearing) Supercharger speed 7 times crankshaft; rated power at 1600 m.
 * Asso XI R.C.40:Supercharger speed 75/7 times crankshaft; rated power at 4000 m.
 * L.121 R.C.40:A version of the Asso XI, 671 kW
 * A.120 R.C.40: Inverted version of the L.121

Applications

 * CANT Z.501
 * CANT Z.505
 * CANT Z.508
 * CANT Z.1007
 * CANT Z.1011
 * Caproni Ca.124 idro
 * Caproni Ca.134
 * Caproni Ca.135
 * Caproni Ca.405
 * Caproni Campini N.1
 * IMAM Ro.45
 * Piaggio P.32
 * Piaggio P.50
 * SAI Ambrosini S.S.4
 * Savoia-Marchetti SM.79 (originally)