Heavy fuel engines

Heavy fuel engines

Key features of 3W – Modellmotoren´s Heavy Fuel System

  1. Modified air intake system including velocity stack.

  2. Modified diaphragme carburettor

  3. Pre heating system for crankcase by using cartridge heaters and heat collector (s )

  4. HF engines run 30° – 40°C cooler than gasoline engines

  5. Fuel consumption of HF engines is approx. 20% lower and more compared with gasoline engines of the same class.

  6. Compression ration was reduced to 1:8,5 instead of 1:10 / 11 at gasoline engines. The lower compression means less load of all rotating parts and a soft running characteristic which reduces the vibration level. The life time of the engine will be increased.

  7. For the Cold Start the cartridge heaters will be powered up for 3-4 minutes by an external power supply until the starting temperature of + 65°C is reached under the spark plug. When the engine is running the external power supply of the cartridge heaters is switched off. No external power source is needed any more. The system will keep the engine warm.

  8. Due to the fact that the Heavy Fuel is activated in the pre heated crankcase the fuel does not get vaporized in the carburettor. The conclusion of this effect : the carburettor operates like a mechanical fuel injection pump.

  9. To reduce the fuel consumption of Heavy Fuel , it will be pre heated. This is done automatically when passing the heat collector (s). If this feature will be used, it requires the intake housing ( reed housing) made of aluminium.

  10. 3W-ignition system is used

  11. Standard cylinder and pistons can be used.

1 – cylinder Heavy Fuel – Engines

As an example our 3W-28xi / 30xi HFE. The 2 coloured pictures show the special designed muffler with integrated heat collector and 3 cartridge heaters.

3w28-xi-hfe


3w28-xi-hfe


2 – Cylinder HF – Engines

All HF- Engines with a cylinder capacity of 34ccm and more are designed and produced as TS cylinder : Twin Spark which means2 spark plugs per cylinder. This concept will increase a more reliable and save operation of the engines. In case 1 ignition box will break down, the 2nd. box will keep the engine running. Test have shown that the RPM will be reduced by only approx. 150 RPM.

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3W-56iB2 HFE

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3W-56iB2 HFE

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3W-110xiB2 TS HFE

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3W-110xiB2 TS HFE

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3W-157xiB2 TS HFE

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3W-157xiB2 TS HFE

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3W-210xiB2 TS HFE

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3W-210xiB2 TS HFE

Heat collectors with cartridge heaters and exhaust pipes are shown as well as the rear out put shaft and the fuel pre heating system ( 2 fuel fittings, input and output ) . Fuel is supplied from the tank into the intake fitting , through the heat collector and out into the carburettor. To keep the temperature of the pre heated fuel as constant as possible, the intake housing has to be made from aluminium.

Crankcase Design Heavy Fuel Engine

The casted crankcases are made of 4 parts.

  • Frontcrankcase

  • Maincrankcase ( 2 parts )

  • Engine mounting plate

This design allows a precise and save machining of all ball bearing seats.
The front crankcase can be supplied in a stretched version. This requires a new longer front crankcase ( new casting ) in combination with a longer front crankshaft ( new forging ). To support the long front crankshaft an additional ball bearing is mandatory.

The engine mounting plate is designed for mounting an additional 4 th. ball bearing to support the rear output shaft. If an alternator or alternator / starter unit will be used , only the mounting plate has to be redesigned to meet the specifications of the customer. Mounting plates for Bental and Sullivan units are available for 3W-110xiB2 TS HFE and 3W-157xiB2 TS HFE.

Automatic compression release valve

Besides the manual operated valve this feature is also available. Starting on the ground is easy and reduces the load of the crankshaft when a heavy duty external electric starter is used. Whilst flying the engine can be stopped and easily restarted in the air if an onboard starter or alternator / starter unit is on board.

Muffler for Heavy Fuel Engines

To reduce the noiselevel the patented 3W-mufflers are part of the delivered engine package. Upon request these mufflers can be supplied , coated with a special carbon looking foil. This special foil reduces the heat signatureof the muffler body. The foil is heat resistant up to +180°C.

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