[Christ]

I'd agree with you, if we were talking about an engine that was designed for anything more than bench testing theories.

Regardless of what you think of the results, engineers and engine builders alike both know that hotter intake air will decrease efficiency of diesel engines. The vaporized fuel likes to be surrounded with as much air as possible, in as dense a situation as possible, to ensure a complete burn.

I'm also well aware that diesel engines run "lean" as it were. They all do. If you take the total fuel consumption in a given power stroke, and compare it to the total volume of intake air at a given RPM, you can come up with a basic AFR.

In order to measure real-time AFR, you'd have to know how much fuel was being injected at any given millisecond, and compare it to the air intake at the intake stroke prior to the beginning of the power stroke you're measuring. AFR in a diesel gets increasingly richer from a starting point of nil, so on an AFR map, it would show that the further the piston has traveled, the more fuel has been burned, and the AFR is closer to stoich with each degree of crankshaft rotation until the end of the injection event.

The "Fixed reference point" of our experiment was showing the EFFICIENCY (not output specifically, but output per unit of fuel) of the engine, not the power. Keeping the injection timed so that it always occurred at the same time in relation to the piston's stroke was actually optimal for the situation, since 0 load was the requirement for the study, and therefore, load adjusted injection timing was not necessary. Once again, the only reason for measuring torque output was to approximate a variance in efficiency based on intake temp.

When we observed that there was not as much torque output with the increasing intake temp, we began to add more fuel (secondary experiment) until the torque output "came back" to where it was in the control, with the intake/fuel temps at room temp, and the injection timing held accordingly. We actually never got the same output with the warmer air, even though we scaled the fuel in increments until the engine actually stalled before we could measure it's output.

Engineers and Engine builders alike will stand by these observations. Diesels like it cold, no two ways about it.