What is the difference between a diesel and a petrol engine in how they propel the vehicle?
Both types of engine have cylinders that fill with the vapour or spray of their respctive fuel, but this is ignited in different ways and under different conditions. You are right that diesel engines do not have spark plugs. Fundamentally, both types of engine burn the relevant fuel, which makes the pistons expand, pushes a section of a crank down and gets the engine turning. The rotary motion is transfered via the gearbox to the wheels and the car drives. So the answer to your question is really that they propel the vehicle in exactly the same way. Petrol engines usually rev higher than diesel engines, and the majority of the power is at the top end of the rev range, meaning that you get a quicker accelleration the higher engine is revving. A diesel has never really been able to rev as high as a petrol engine, and some modern ones can only rev up to a speed of about 4,500rpm. The difference with modern ones is that the power is much lower in the rev range, meaning that there is a much
