Modifying cruise control to flow lph instead of maintaining speed

[dieselmech]

I think the thought process is, place a limit on the amount of fuel to be consumed. ie, 30L per hour. That equates to 2000rpm at light load for example. If the load or rpm changes, the fuel consumption remains steady.
2000rpm/light load
1800rpm/heavier load
2200rpm/lighter load
There are many problems with this idea though. The engine requires a proper air/fuel ratio. To arbitrarily limit fuel flow would require the engine to modify the throttle settings according to the oxy sensors. Sensor reads lean (actually more air) then it would reduce throttle setting to achieve proper ratio. Sensor reads rich (lack of oxygen) then would open the throttle to achieve proper ratio.

That is REALLY an back-asswards way of doing something. Besides the properly working computerized systems (proven) out there right now compared to this untested theory, you also have the problem of adjusting something unrelated to achieve a goal.
Kind of like leaving the throttle set wide open and pulling spark plug wires off and on to vary hp to match the requirement.

The best way to limit fuel consumed is to monitor it yourself. Cruise works on flat ground, use minimal throttle on hills.