Vehicle technology has provided us with massive opportunities for fuel saving over the past few years. The benefits of electric vehicles, platooning and other wellpublicised factors are still in the future for New Zealand operators for the most part. But significant fuel saving benefits are available to conventional trucks (including some older models), and manufacturers have been making subtle improvements, which should be considered when upgrading trucks or reconfiguring them for a different role.
The introduction of electronic engine management made it easier to control engine operation and, to some extent, override the driver’s influence on fuel consumption. The engine control module (ECM) can be reprogrammed, either by an approved agent or an unauthorised technician, although unapproved changes are likely to affect any manufacturer’s warranty.
But engine electronics go well beyond determining how much fuel to deliver to the injectors. Listed below are some of the ECU-controlled features Cummins has come up with to help reduce fuel consumption.
Load-Based Speed Control (LBSC)
LBSC is a Cummins’ feature that limits the engine rpm when not needed – to save fuel and reduce driveline wear. When needed, LBSC will allow the engine to operate at full-governed speed when carrying heavy loads and/or on moderate grades, or when making gear changes. But the system can adjust the engine speed available to the driver. The ECM looks at the load and sets the rpm limit accordingly.
Cummins say LBSC encourages proper driving techniques and improves fuel economy, and it can reduce the variability between the least efficient and most efficient drivers in a fleet of similar trucks.
Vehicle Acceleration Management
Fuel consumption increases significantly during hard acceleration. VAM helps eliminate excessive acceleration, thus allowing the vehicle to accelerate at a continuous rate.
This reduces wear on the driveline and results in better fuel economy.
Road Speed Governor (RSG) and Cruise Control
RSG is used to set road speed; a lower road speed limit almost always improves fuel economy significantly. Cummins point out that as a rule of thumb, each 2kph increase in vehicle speed above 90kph decreases economy by nearly 2%.
Using cruise control to maintain a desired road speed eliminates throttle input variance and improves fuel economy.
Tiny movements in throttle position have a disproportionate on fuel use.
(GDP) GDP helps maximise running the transmission in top gear.
Operating an engine at higher revs than necessary results in increased fuel use; maintaining top gear for the maximum length of time and keeping revs down in lower gears saves fuel.
GDP will keep the engine operating at lower revs for better fuel economy and engine life. W hen the driver downshifts, the GDP cuts back on the top speed, to encourage the driver to stay in top gear if possible.
GDP can be used in conjunction with LBSC to limit engine operating speeds throughout the vehicle’s entire operating range.
Correct gearing is vital for optimum fuel consumption.
Cummins say an engine geared to run at 1600rpm at 100kph gets approximately 2.5% better economy than one geared to run at 1700rpm. But they point out that optimum gearing is based on a number of factors, including an engine’s peak torque range, the speed the truck is likely to operate at, and tyre size. They add the vehicle should be geared to operate at the manufacturer’s recommended rpm at whatever road speed the vehicle will spend most of its time.