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The 3701 is Hirth's first offering of a water-cooled engine
for the aircraft market. 3701 is offered in 2 versions ranging from 80 to 100
hp allowing the same basic crankcase to be used in a wide variety of
applications. A narrow engine profile with a single tuned exhaust used for all
3 cylinders allows the 3701 to be used in compact engine compartments. Pistons
fire 120 degrees apart resulting in very quiet & smooth operations.
3701 incorporates Al-Nikasil coated cylinders for
superior performance and reliability. Nikasil provides for a super low
coefficient of friction, reducing engine heat and wear. The pistons and
cylinders expand at the same rate thus providing for a seizure resistant
engine. 3701 crankshaft is 4130 chromemolly steel. Heads, cylinders, rings,
block casting, connecting rods and associated components are all of the highest
grade alloys available today.
Model: |
3701 |
Carburation: |
Electronic fuel injection |
Engine Type: |
2 cycle, 3 cylinder |
Fuel Pump: |
Electric fuel pump. |
Bore: |
76mm |
Lubrication: |
Fuel mixed with oil @ 50:1 or optional oil injection |
Stroke: |
69mm |
Rotation: |
Counter clockwise, viewed from output end |
Displacement: |
939cc |
Starter: |
12 volt electric, |
Compression: |
9.5:1 |
Cooling: |
Water cooled |
HP Output: |
100Hp @ 6000Rpm |
Weight: |
108 lbs- including electric start and exhaust. With optional gearbox
127 lbs. (does not include radiator) |
Peak Torque |
88 Ft.Lbs @ 5500Rpm |
Reduction Units: |
G-50 gearbox available in 2.16:l, 2.29:l, 2.59:l, 3.16:l and 3.65:l
ratios or optional G-40 gearbox can be used if clutch is required. |
Ignition: |
Dual CDI |
Drive Coupling: |
Elastomeric dampener with G-50 gearbox or optional centrifugal clutch
with G-40 gearbox. (2.03:1,
2,25:1, 2.64:1, 2.96:1. 3.33:1) |
3701 is offered in two separate Hp versions. This is done
through engineering by changing the piston port timing. Placement of the port
timing determines what Rpm the peak torque is achieved. When peak torque is
arrived at low Rpms the peak Hp of the engine is less but the torque curve in
mid range is very flat. Such an engine gives up some thrust at full power but
has high torque in the mid range allowing for very low engine RPM at cruise
power settings.
The same engine with the port timing set high will
produce much more Hp and thrust at full power. Peak power is at a higher Rpm
which means that the cruise Rpm will also be at a higher Rpm. By offering the
3701 with two different Hp ratings it will be possible to choose the power
requirement that best fits the application.
3701 High torque/low rpm engine - Peak power - 80 Hp
at 4500 RPM. (Not available until April 03)
3701 High performance engine - Peak power - 100 Hp at
6000 RPM