Yes. Even though the overall A/F is lean, the nature of the Diesel combustion process is that of a stratified charge process. This, to simplify, means that overall while there is just air in the cylinder, as the fuel is injected, the charge is locally closer to stoichiometry (which burns pretty hot). So, when you have high temperatures and plenty of excess O2, you get high NOx production.
You are misinterpreting the specs. Variations in ambient atmospheric pressure are known to cause variation in fuel octane characteristics, therefore the test specifies that atmospheric pressure be controlled. It does not mean there is a heavy load on the engine. The standard atmosphere pressure that the test protocol requires to be maintained at air inlet is not the same thing as manifold pressure. They also control for humidity and temperature. Read the ASTM literature.
Like any other gas/carb/spark engine the engine speed is limited by the intake air flow. And the air flow restriction on the test engine is designed to simulate an engine under light load conditions. That's how the ASTM describes their test set up. And yes the test is designed to run at a constant RPM for all tests so the engine is connected to a synchronous electric motor which can keeps the RPM's constant even when fuel/air supply can't - like when the engine is knocking heavily or converting from one test fuel to another.
But the test methodology is a distraction from the point. The point was the test results (the RON octane number) aren't revealed to the public. So you don't know what the RON octane is for the fuel in your tank.
-jim
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the effect of the turbo varies essentially with the amount of *fuel* being burned, because the fuel comes into the engine as a liquid (atomized, but still) and the combustion products are all gases. So the volume of gas going through the turbo is dependent not only on engine speed, displacement, and VE (with no fuel at all being injected, this would determine the amount of gas passing over the exhaust turbine) but also the amount of fuel burned and the resultant temperature (remember, pv=nrt)
so basically, unless you did well in thermodynamics, trying to figure it out exactly will make your head hurt :) (I think I got a B or C in all of the thermo classes that I took, and now I need another cup of coffee...)
nate
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