ALT-1 What are the Differences between Diesel and Gasoline Engines
There are many differences between a diesel and gasoline powered engine. The obvious difference is the fuel. Diesel fuel has been historically less expensive to refine than gasoline, thus it has always been available as a lower cost fuel. But the fuels behave differently in internal combustion engines, thus require different mechanical designs to utilize their stored energy.
Diesel engines contain no spark plugs. The fuel ignites in the combustion chamber due to spontaneous combustion. The fuel and air mixture is compressed by the piston as it travels upward, ultimately causing the mixture to rise above it's flash point and exploding. A gasoline engine will also compress the fuel air mixture, but a spark is used to ignite the fuel. Diesel engines do use glow plugs to preheat the fuel & combustion area in cold weather. Diesel engines can be more difficult to start in cold weather.
Diesel engines are also more fuel efficient, and convert more stored fuel energy into mechanical energy than gasoline engines. Fine tuning a gasoline engine was once much easier, and less costly. However today's computer controls allow both engines to perform equally as well.
As a whole diesel engines are a bit more noisy than gasoline engines. This is due to the size of the combustion chambers, amplification of combustion, and having a more powerful combustion process.
Diesel engines do not develop as much vacuum as gasoline engines due to the size of the pistons and compression ratios. Thus an external vacuum pump is often needed to run auxiliary devices such as HVAC dampers, EGR valves, etc.
The recent increases in Diesel fuel prices may steer some towards gasoline engines. However the long term cost benefit may still be in the favor of diesel fuel.
