[KLS]

Leland,
Gasoline engines usually don't have cooled pistons. The heat of combustion on the piston crown is passed through to the bottom side and into the air in the crankcase, and also through the piston rings into the cylinder wall and thence to the coolant. Gasoline engines running lean at idle won't overheat...gasoline engines running lean at high power levels will soon melt the aluminum piston crowns. Most (all?) diesels have cast iron pistons, and bigger ones have replaceable forged steel piston crowns bolted on.

Many diesel engines have cooled pistons, either an oil spray on the bottoms, or oil circulating in cooling passages in the piston, or in a few cases, cooling water circulating in cooling passages in the piston. On a diesel, as the load increases, the air-fuel ratio decreases. The beginning of injection is later at light load and earlier at heavy load. The ending of injection is much later at heavy load.

Makana,
A turbocharged diesel engine will get more air as the engine's load increases and the hotter exhaust gases drive the turbocharger faster. More load, even at the same rpm, and more air is pushed into the intake. This is really noticable on a diesel generator where the speed is kept constant, and when more load is added the turbo can be heard to speed up. The turbo boost gauge shows this, even on my turbochaged Volvo running on cruise control...same rpm, come to a slight hill, and the boost increases.


Ken