Sport aviation engines for Ultralights, Homebuilts, Kitplanes, Gyrocopters, Helicopters, Powered Parachutes, Trykes, Hovercraft & Air Boats.

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3702 - 3 cylinder - 2 cycle liquid cooled 84hp

The 3702 is Hirth's water-cooled alternative to the popular 3003 air cooled engine. 3702 is offered carbureted or with optional fuel injection. Standard engine is pre-mix and oil injection is available for either the carb or fuel injected versions. A narrow engine profile with a single tuned exhaust used for all 3 cylinders allows the 3702 to be used in compact engine compartments. Pistons fire 120 degrees apart resulting in a very smooth power curve. 3702 fuel consumption rivals similar Hp 4 cycle engines.

3702 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. 3702 crankshaft is 4130 chrome molly steel. Heads, cylinders, rings, block casting, connecting rods and associated components are all of the highest grade alloys available today.

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3702 - 84Hp electric start &
3 carburetors.
$9997.00
3702 - 84Hp elec,st, carbs & G-50 gearbox
$11,314.00
3702 - 84Hp electric start &
fuel injection.
$11,994.00
3702 84Hp with elec, start, fuel inj. & G-50 gearbox
$13,311.00
Oil Injection Option
$498.00

Hirth's latest design.

Model:
3702
Engine Type:
2 cycle, 3 cylinder
Bore:
76mm
Stroke:
69mm
Displacement:
939cc
Compression:
9.5:1
HP Output:
84Hp @ 4950Rpm
Peak Torque
87 Ft.Lbs @ 4300Rpm
Ignition:
Dual CDI
(Capacitive digital Ign.)
Carburation:
Triple 34mm slide or optional electronic fuel injection
Fuel Pump:
Auxiliary external pneumatic - 12VDC with fuel injection
Lubrication:
Premix – 50:1 or optional oil injection
Rotation:
Counter clockwise, viewed from output end
Starter:
Alternator:
12 volt electric,
250 watt/20 amp alternator standard
Cooling:
Liquid cooled
Weight:
108 lbs- including electric start and exhaust. With optional gearbox 127 lbs. (does not include radiator)
Reduction Units:
G-50 gearbox available in - 2.16:1, 2.29:1, 2.59:1 ratios or optional G-40 gearbox can be used if clutch is required.
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)


3702 is the high torque low RPM version of the 3703 engine. 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.

3702 High torque/low rpm engine - Peak power - 84 Hp at 4950 RPM.


Engine Print



Customer Photo Gallery




3702 installed on MX II
Picture #1 Left Side
Right Side




3702 installed on Earthstar Thundergull II
Picture #1 Left Side
Right Side



3702 installed on Dolphin Floatplane
Picture #1 Left Side
Right Side




3702 installed on Skymaster PPC
Picture #1 Left Side
Right Side Rear View




3702 installed on Gyrocopter
Picture #1 Left Side
Right Side



3702 installed on Infinity PPC
Picture #1 Left Side
Right Side




3702 installed on Fusion PPC
Picture #1 Right Side




3702 installed on Skyboy
Picture #1 Left Side
Right Side



3702 on Genesis Aircraft
Picture #1 Picture #2
Picture #3 Picture #4