[Christ]

Jyden -

A few points to consider for you:

1 - You can't maintain the same speed at a lower RPM without gearing changes, making the extra power you've just generated a burden to the general operator, because who's really going to calculate and regear to make up for 2 extra HP?

2 - The engine still experiences greater pumping losses by drawing colder air due to the air's specific density.

3 - The ECM will compensate on either side of the scale, but as you note, more cold air means more fuel, while more hot air means less fuel. If your engine is capable of making more power at your cruise RPM than is necessary to maintain cruise, you're wasting efficiency as high pumping losses. To recoup those losses, you open the throttle, but under normal circumstances, that would cause you to accelerate, which is undesirable. The acceleration comes from more air/fuel being added to the cylinders. This means that in order to mitigate pumping losses without making any more power, you have to throttle the air in different ways, such as thinning it. This requires pre-heating it.

4 - At every instance in your graphs, you're showing gains of 1-2 HP in ranges that are desirable to normal driving situations. Of course, knowing how dyno setups actually work, and without evidence that multiple runs were made and averaged, I'm going to dismiss the results entirely as being within the realm of noise, but assuming for a minute that I don't, you're still making more power at the same RPM, which, in the case of adding cold air/more fuel, is neither more efficient per unit of fuel, nor is it desirable for optimum operation involving fuel per distance calculation.

To clarify - when you add cold air and more fuel, you're not doing anything the engine wasn't already doing, you're just giving it more of what it needs to make power. If you were to maximize the power output from the same amount of fuel it's already using, then you're making it more efficient at doing it's job, converting liquid fuel to heat energy, and that could translate into somewhat better FE, despite the lower throttle angles that would be necessary to maintain the same speed.