Franklin O-175
# Franklin O-175

The Franklin O-175 (company designation 4AC-176) was an American air-cooled aircraft engine of the 1940s. The engine was of horizontally-opposed four-cylinder and displaced 175 cu in (2.9 L). The power output was nominally 80 hp (60 kW). A later variant was designated O-180, despite sharing the same displacement.

A related four-cylinder engine of slightly smaller capacity was known as the O-170 or 4AC-171. It produced 60 hp (45 kW).

## Variants

### O-170

**4AC-171**


    60 hp (45 kW)

### O-175

**4AC-176**


       4AC-176-B - 65 hp (48 kW) at 2,200 rpm
       4AC-176-BA/(O-175-1) - 65 hp (48 kW) at 2,300 rpm
       4AC-176-C - 75 hp (56 kW) at 2,500 rpm
       4AC-176-D - 80 hp (60 kW) at 2,650 rpm
       4AC-176-F - 80 hp (60 kW) at 2,500 rpm

## Applications

* Aeronca L-3D
* Bowyer BW-1 flying wing
* CAP-4 Paulistinha
* Harris Little Jewel
* Interstate Cadet
* IPT-7 Junior
* Jensen Sport (O-170)
* Johnson-Funke monoplane
* Langley Twin
* Piper J-3 Cub
* Piper J-4
* Piper L-4
* Porterfield Collegiate
* Taylorcraft BF-60 (O-170)
* Taylorcraft BF-65

## Specifications (4AC-176-BA2, O-175-1)

Data from Wilkinson

### General characteristics

* Type: 4-cylinder air-cooled horizontally opposed aircraft piston engine
* Bore: 4 in (102 mm)
* Stroke: 3.5 in (89 mm)
* Displacement: 176 cu in (2.88 L)
* Length: 28.6 in (726 mm)
* Width: 30.2 in (767 mm)
* Height: 20 in (508 mm)
* Dry weight: 182 lb (82.6 kg)

### Components

* Valvetrain: OHV, 1x inlet valve, 1x exhaust valve operated by pushrods
* Fuel system: 1x Marvel-Schebler MA-3P updraught carburetor
* Fuel type: 73 octane gasoline
* Oil system: Pressure system at 40 psi (3 bar), wet sump
* Cooling system: Air-cooled

### Performance

* Power output: 65 hp (48.5 kW) at 2,300 rpm for take-off
* Specific power: 0.37 hp/(cu in) (16.837 kW/L)
* Compression ratio: 6:1
* Specific fuel consumption: 0.49 lb/(hp h) (0.298 kg/(kW h), 220 US gal/(hp h)) cruising
* Oil consumption: 0.003 lb/(hp h) (0.0018 kg/(kW h), 1.4 US gal/(hp h)) cruising
* Power-to-weight ratio: 0.357 hp/lb (0.587 kW/kg)
