PhilForce said:
A good article can be found here if you want to read a lot about it:
http://www.howstuffworks.com/diesel1.htm
Hopefully someone can who knows more about it can break it down to simpler terms.
I don't know if I can but I'll try...
Having been a diesel technician for going on ten years, diesel technology is something I enjoy talking about.
If you read the link above you know now that diesels and gasoline engines are similar in design. They all rely on the same theory...internal combustion driving a piston, which turns a crankshaft. What's different between the two is how they create that combustion.
Simply put, combustion is fire. Fire relies on three things in order to exist. Heat, oxygen, and fuel. The two engine designs are similar in the oxygen and fuel categories in that, both rely on intake valves of some sort, and both rely on injectors or some other way of introducing a fuel source into the cylinder above the piston.
The last element, heat, is where the two engines vary differently. Gasoline engines use a spark plug, obviously, but Diesel engines use heat from compression. A Diesel piston will compress the air in a cylinder sometimes 20:1 which causes an immense amount of heat, enough to ignite the fuel injected into the cylinder.
After this the theories of the two engines are back to being the same and the cycle starts over again.
Trust me I could go on and on and on about fuel system theories and such but it would probably take all night.
Basically, to try to put it as concise as possible, higher fuel pressures mean smaller atomization of fuel as it enters the cylinder. Smaller "drops" of fuel means more complete burn of the fuel before it's shoved out the exhaust. A more complete burn means much cleaner emissions, better fuel economy, and more power.
I hope this helps and I haven't muddied the waters even more. I tried not to repeat the link above too much.
Any questions let me know!
Seth
