Isuzu Commercial Vehicles - Low Cab Forward Trucks - Commercial Vehicles

The piston is the center of the engine and a very important moving part. It was important to maintain the reliability and durability of the 4H engine when designing this important core area of the engine.

The market trend demand for high output and high performance from engines means that it is critical to see how far the piston temperature can be lowered. The ability to lower the temperature will allow the engine to achieve these market needs.

Diesel engines are very famous for having high thermal loads and high combustion pressures. If the proper countermeasures for the increasing thermal load are not adequate, the following effects will be seen:

Engine power output will drop
Blow-by gas quantity will increase
Oil consumption will increase
Engine noise will increase
Seizing could occur in the cylinder bore

All of the above are results which reduce the attractiveness of diesel engines. In order to avoid these results, an adequate oil cooling system is necessary. The 4H has been designed with high performance cooling throughout the engine.

High piston temperatures outside the operating range also can cause the material strength to drop. This is dangerous as the following could result:

Component cracking
Oil carbonization in the ring grooves
Ring sticking
Piston seizing

To optimize piston cooling the following features are implemented in the 4H engine:

Sufficient cooling channels designed within the actual piston
Selecting the optimum architecture of the cooling system
Obtaining a temperature balance between the oil inlets and outlets
Obtaining the required oil volume

Computer aided engineering (CAE) has also been thoroughly used in the design of the 4H oil cooling system. The final design of the 4H makes it possible to keep the temperature of the piston head and ring grooves low even at high loads. The end result to the customer is increased engine reliability and durability.

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