i understand that diesel engines are used in heavy duty vehicles and gasolines are usually used in cars.why are diesel engines preferred for heavy duty? and who are some cars using diesel engine, like some VW models that use clean diesel.i know the engine works a bit different between diesel and gasoline but as for performance, why is one preferred over the other for heavy duty and regular cars?
a diesel engine develops so much more torque compared to a spark ignition engine. given that the typical engine has a compression ratio of about 12:1 MAX and a diesel is roughly 18 to 22:1, when you ignite the air fuel charge by any means that compressed gas is what does every thing, in a spark ignition engine that air charge expands to 4 times its volume. i do not have a diesels ratio but there can not be much of a difference. that 12 to 1 now be comes 48 to one in a very small area forcing that piston to move. in the diesel with a 20 to one compression ratio, now 80 to one putting an immense force on the face of that piston. so muck torque is developed. i have no info on the clean diesels, so i will stop, but diesels are known for the smoke in the exhaust whick is particulate matter in the air that will settle out.
Diesel engines ignite the fuel by compressing the fuel to a point where it combusts, instead of using a spark like gasoline engines. That's because diesel and gasoline have different properties: Diesel isn't easy to ignite with a spark, but gasoline is, cause diesel has a higher flashpoint. So because diesel engines have to have higher compression, they have longer strokes, so more torque. This helps increase how much weight the engine can pull, which is why all tractor trailors, ships, or anything heavy duty has a diesel engine. Only ships that don't have diesel engines have electric motors because they have a lot ot torque as well, but even those ships have diesel generators. Diesel engines are used in VW's because they use a lot less fuel. Also they last longer because diesel helps lubricate the engine. So in regular cars, they help acceleration (more torque), fuel economy, and engine life. In heavy duty vehicles, they also help fuel economy (but still use a lot), towing capacity, and engine life.
The difference between Petrol and Diesel engines are not as big as they used to be. In the past, a Perkins diesel engine was very very slow, very very noisy, very dirty and heavy. But now there is little difference between the two. The introduction of the Turbo has been a great help. You just have to look at the BTCC last year. Jason Plato's Seat Diesel was incredible.
