What does running at unnecessarily high speed do to fuel consumption and engine life?
A diesel running at a higher speed than the job requires burns more fuel, produces more noise and vibration, and wears faster because its moving parts complete more cycles per unit time. Doing the job at the lowest suitable speed lowers both consumption and wear; electronic throttle control makes it easy to set that point steplessly.
Fuel consumption rises noticeably as speed increases; if you can do the same job at a lower speed, the gain is direct. In addition:
- The piston, bearings and valve train complete more cycles per unit time; wear accelerates.
- Noise and vibration increase, raising operator fatigue and loosening connections.
- On a piston pump the speed directly determines the flow; flow beyond what is needed generally returns through the relief valve, meaning fuel is converted into heat.
There is an opposite extreme too: running for long periods at very low load increases the risk of wet stacking on a diesel. The right approach is to find the speed the job requires and stay there.
On the GS740 you can store the working speed in memory by holding the button for 3 seconds, and switch instantly between idle and that speed with a short press. Dropping the engine to idle during waits between runs is the most practical way to cut consumption. In drilling in particular, even idle consumption has been measured as considerable; so the cost of leaving the engine waiting at unnecessarily high speed is by no means small.
The full topic: Electronic speed and throttle control on a diesel engine