Diesel engine basics by professor 83bj60 
Ok!
Turbos compress the air,
Yes.... by up to 100% for most diesels (when the boost is 14 PSI above standard atmospheric pressure of about 14 PSI)
Air gets hot with friction,
Yes, but the turbo heats it up mostly by compression, and partially by heat conduction from the exhaust gasses through the body of the turbo itself.
A Diesel motor is Compression ignition, hot air that takes up more space is great!!
No, hot air entering the engine is less dense therefore has less oxygen, which reduces its potential for burning fuel, hence its potential for producing power.
One thing to remember is that heat generated by compression reaches about 800C which is more than enough to ignite the fuel when it is injected in the combustion chamber at the end of the compression cycle.
On a sidenote, it is incorrect to assume that air cooled by an intercooler down to let's say 20C from let's say 120C, will, when compressed in the engine, be 'cooler' than if it is not intercooled, because denser air will reach higher pressures when compressed by the same amount, therefore the heat of compression will stay practically the same. In other words, an intercooler is in fact just a device to increase the amount of available oxygen injected in the engine, so that more fuel can be burnt and more power can be produced.
To sum it up, a compression ignition engine works by compressing the air to a temperature where it will spontaneaously promote fuel combustion. The higher the compression and the greater the amount of air available for compression (by the use of a tubocharger and when available, an intercooler), the greater the potential to burn fuel and therefore, the potential for energy output.
Absolutely! Gas engines behave differently by design, by the fact that in diesel engines, air is always fully available at the intake, only fuel injection amount varies. One of the best examples is that at idle, a diesel will burn almost no fuel at all (a cup of fuel in 20 minutes for a 3.4 luitre 3B, for example, which is less than a litre per hour), which corresponds to fuel to air ratios on the order of 1/300 (amount of fuel consumed divided by amount of air ingested) whereas a gasoline or ignition engine
must maintain a stoïchiometric ratio for proper combustion (proprotion of fuel to air of about 1/14) which will make it burn more fuel at idle which can overheat it. On the other hand, diesels will have a tendency to use so little fuel in that condition that they will tend to cool off too much, especially on extended idling in cold weather, to a point where engine temperature will drop so low as to cause cold engine unburnt fuel conditions (soot), which is in reality just as bad if not worse (soot is an abrasive)as overheating in the gasoline the engine.
Blah, blah, blah......I drove a diesel once with a blown charge hose, blah, blah, blah......felt the difference Turbos do it better, forgot what I said, blah, blah,,
Actually, automotive diesels should all be turbocharged. The reason is, that at higher engine revolutions, the movement of the air intake is so fast there is a vacuum condition created in the intake which can actually starve the motor or air hence less fuel can be burnt. That is the main reason why older diesels smoke under high load: insufficient air.
In stationary application, it is not as important. A stationary engine tends to be very large for its output and is designed to run at its most efficient engine revolution setting, where the air and fuel burns most effeiciently.
One thing to remember is that the higher the engine revolution for a given engine piston stroke (downward motion) and fuel charge, the lesser the energy than can be fully extracted during the downward stroke and the more will escape in the exhaust, hence the lower the fuel efficiency.
Another adavantage, turbocharging allows more air in therefore for a given fuel charge will allow hotter and faster combustion therefore more time for the engine to utilize that power before it is lost in the exhaust, hence greater fuel efficiency. In fact it can be said in other words that some of the otherwise wasted exhaust gas energy is converted into useable power in the engine.
Another apsect of engine desgn which is used in large diesels such as those in large trucks and especially, stationary or marine engines to extract more energy is the use of longer piston strokes: in that design there is more expansion allowed hence the exhaust gas temperature will be lower and more of its energy will be transfered directly to the crankshaft. unfortunately this design makes for much larger parts, which means more weight and more importantly, greater centrifugal forces which can destroy the crankshaft sels, so these engines don't have a very wide usueable engine revolution range, which limits their useful range of application for automotive use (which is why large trucks need so many gears).
Hope I didn't lose you there, hope this helps!!!
