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Brief description

Brief description

The diesel engine is an transversely mounted, fluid-cooled, 4-cylinder in-line engine with 4 valves per cylinder, 1 overhead camshaft and 2 balancer shafts. The balancer shafts are mounted in a bearing bridge under the crankshaft. The engine has direct injection, which means that the fuel is injected directly into the combustion chamber, and turbocharging to obtain a high torque within the normal engine speed range. It is also of cross-flow type, i.e. with the inlet passages on one side of the combustion chamber and the exhaust on the other.

The total swept volume of 2.2 litres delivers, together with the turbocharger, a high torque even at low engine speeds, which is advantageous when driving in normal traffic conditions.

The balancer shafts suppress vibration and the forces from moving parts in the engine while lowering the level of engine noise.

Principles of operation, diesel engine

A diesel engine has four strokes, intake, compression, power and exhaust, but does not have spark plugs to start the combustion of the fuel/air mixture. Instead, the engine is designed with high compression and specially shaped combustion chambers.

The principle is that air enters into the cylinder and is compressed. During the compression stroke, the air reaches such a high temperature that the fuel mixture self-ignites when injected and expands to give the power stroke. The exhaust stroke takes place as normal.

The engine works with air and fuel being mixed just before it is injected into the compressed air. In addition, there is no throttle body, so the air is free to flow continuously. Instead, the engine speed is regulated by a high-pressure distribution pump that delivers the correct amount of fuel to be injected into the cylinder at the right moment. This pump is controlled by the engine control module, which, in turn, is informed of the accelerator pedal position and then makes a calculation. After the calculation, the control module sends a request to the pump control module for a certain amount of fuel. The amount of fuel then determines the engine moment.

A diesel engine is normally about 30% more efficient than a petrol engine. This means that fuel consumption is lower than for an equivalent petrol engine.

Mechanically, a diesel engine is constructed in much the same way as a petrol engine, with crankshaft, connecting rods, pistons, camshafts and valves, but lacks an ignition system and throttle body. As the engine does not have a throttle body, there is no way of connecting hoses for vacuum servo, etc. This means that there must be a separate vacuum pump.