Increased fuel consumption using headlights

[oldcro]

Why not replace the headlights with calcium carbide lamps (with automatic water feed and remote ignition) and gain a extra 20mpg.

 

[stevesey]

The cylinder will fill with the same amount of air charge whether under load or not, so greater density equals more oxygen so more output as it ignites.

You can feel the additional performance when driving in cold fog at partial load, not only full load.

Not quite what I was thinking about (this could get long and complicated).

Yes a more dense charge = a bigger bang, so more power. But the ECU will know the air is more dense (from the intake temp sensor) and so inject more fuel to match the extra O2 in the air (if it didn't you'd just be weakening the mixture). So at a fixed opening of your butterfly valve you get more power from cold air.

But if you are trying to cruise at 70mph (say) you won't need the extra power, so you will lift off and close the butterfly fractionally compared to warm air. So the mass (but not volume) of air/fuel sucked in to produce a bang of size X will be the same when cruising in cold or warm air.

So will efficeincy go up or down (in terms of fuel burnt vs output power) is what I'm trying to get my head around. If the bang is the same, and the rpm, any change in efficency must come down to pumping losses. Are they less or more when sucking in this more dense, but lower volume charge?

 

[Dieselman]

so you will lift off and close the butterfly fractionally compared to warm air.

What butterfly valve. It's a diesel..

 

[Paul S320CDi]

Why not replace the headlights with calcium carbide lamps (with automatic water feed and remote ignition) and gain a extra 20mpg.

That is a good idea. In an emergency you could use the generated acetylene gas from the lamp to do some welding. (assuming you had a bottle of O handy)