title: Isotta Fraschini Asso 750
text: # Isotta Fraschini Asso 750
  
  The Isotta Fraschini Asso 750 was an Italian W 18 water-cooled aircraft engine of the 1930s. Produced by Isotta Fraschini the engine displaced just under 48 L (2,900 cu in) and produced up to 940 hp (700 kW). Together with the Asso 200 and the Asso 500 the Asso 750 was part of a family of modular engines, that used common and interchangeable components to lower production costs.
  
  ## Technical description
  
  The W-18 Asso 750 had three six-cylinder in-line banks made of chrome-manganese steel, each joined by a single cast aluminum head for each bank of cylinders.
  
  ## Operational history
  
  A version with an effective power of 940 hp (700 kW) was optimized for the Savoia-Marchetti S.55X used for the trans-Atlantic flight of Italo Balbo.
  
  ## Variants
  
  ### Asso 750
  
      Direct-drive, unsupercharged.
  
  ### Asso 750 R.
  
      Development with modified crankcase and crankshaft, fitted with a 0.658:1 reduction gear. Maximum power output 940 hp (700 kW).
  
  ### Asso 750 R.C.35
  
      The 750 R. fitted with a supercharger, rated altitude of 3,500 m (11,500 ft).
  
  ### Asso 750 M
  
      A 57.25 L (3,494 cu in) racing development with 150 mm (5.9 in) bore and 180 mm (7.1 in) stroke, for the Macchi M.67, re-designated Asso 1000 Ri.
  
  ## Applications
  
  * CANT Z.501 (early versions)
  * Caproni Ca.111
  * Macchi M.C.77
  * Savoia-Marchetti S.55
  * Savoia-Marchetti S.62
  * Savoia-Marchetti S.78
  
  ## Engines on display
  
  At the Italian Air Force Museum two Isotta Fraschini Asso 750 are exhibited: A direct-drive Asso 750 and an Asso 750 R.C.35 with reduction gear and supercharger.
  
  ## Specifications (Asso 750)
  
  Data from Il motore Isotta Fraschini Asso 750
  
  ### General characteristics
  
  * Type: W-18 liquid/water-cooled
  * Bore: 140 mm (5.5 in)
  * Stroke: 170 mm (6.7 in)
  * Displacement: 47.6 L (2,900 cu in)
  * Length: 2,196 mm (86.5 in)
  * Width: 1,060 mm (42 in)
  * Height: 1,060 mm (42 in)
  * Dry weight: 630 kg (1,390 lb)
  
  ### Components
  
  * Valvetrain: Overhead valves 2x inlet and 2x exhaust per cylinder
  * Supercharger: No supercharger fitted to this variant: supercharger available in other variants - (R.C.35 rated to 3,500 m (11,500 ft)).
  * Fuel type: Gasoline 87 Octane
  * Oil system: pressure
  * Cooling system: Liquid/water
  * Reduction gear: Not fitted to this variant: reduction geared variants available (0.658:1 R. and R.C.35).
  
  ### Performance
  
  * Power output: Normal 800 hp (600 kW) at 1700 rpm; Take-off 850 hp (630 kW) at 1750 rpm; Max 900 hp (670 kW) at 1900 rpm
  * Compression ratio: 5.6:1
  * Specific fuel consumption: 0.295 kg/kWh (0.485 lb/(hp⋅h))
  * Oil consumption: 0.00114 kg/kWh (0.00187 lb/(hp⋅h))
  * Power-to-weight ratio: Normal 0.95 kW/kg (0.58 hp/lb) max 1.129 kW/kg (0.687 hp/lb)
  