Right, you do not need the glow plugs when it is warm, the compression alone will ignite the mixture. Diesel is not like gas, that requires a spark. When a diesel engine is cold, the compression process may not raise the air to a high enough temperature to ignite the fuel on the compression stroke. Compression in diesel motors have compression ratios that are 14:1 to as high as 25:1, with 20:1 a typical ratio.
Diesel motors are more efficient than gas motors, despite the BLACK smoke (unburned fuel) that they emit, or waste. Clean diesels today are even are more efficient in the combustion process, thus much less black emissions.
Peugeot has made a diesel hybrid engine, that is up to 25 percent more efficient than current gasoline hybrid engines. The EPA will be putting emissions controls on Diesels pretty soon...
The funny thing with diesel, is it was only introduced in passenger cars in the USA because of the OPEC oil embargo in the '70s. Also, since all diesel motors HAVE to be Fuel Injected they were a lot more expensive at the time.
Eight reasons why they were not popular:
1: Diesel engines have much higher compression ratios over a typical gasoline engine, so they tend to be heavier than an equivalent gasoline engine.
2: Diesel engines also tend to be more expensive, and people hate working on them, even TODAY because the smell gets on everything and everyone working on it.
3: Due to their weight and compression ratio, they tend to have lower maximum RPM ranges than gasoline engines. This makes diesel engines high torque rather than high horsepower, and that tends to make diesel cars slow in terms of acceleration.
4: Again, diesel engines must be fuel injected, and in the past fuel injection was expensive and less reliable.
5: Diesel engines tend to produce more smoke and "smell funny." That smoke is simply wasted, unburned fuel though, and has improved much.
6: They are harder to start in cold weather, and, if they contain glow plugs, you have to wait before starting the engine so the glow plugs can heat up the cylinders.
7: Diesel engines are much noisier and tend to vibrate. This has changed in newer passenger vehicles...
8: Diesel fuel is less readily available than gasoline, but as an alternative K-1 Kerosene can be used. On that note, I remember a guy pulled up at a gas station with no Diesel, and pulled up to the Kerosene pump. We all told him, HEY, that's a K-1 pump, he just looked at us ans smiled; filled up his Mercedes and drove off.
