1443 Operating Practices

In addition to the daily maintenance check described above, each operator can do several other things to decrease the fuel consumption of his or her vehicle. These measures include eliminating unnecessary idling, warming the engine correctly, choosing the most economical speeds for a given load, keeping the hydraulic system above stall speed, and keeping the cooling temperature within specified limits. The following paragraphs discuss these actions in more detail.

Eliminating Unnecessary Idling

The three largest makers of diesels are unanimous in condemning unnecessary idling as a waste of energy and as hard on the engine, although some idling is necessary.

If equipment will be idled for more than 10 to 15 minutes, the cost for shutdown and restarting the engine will generally be less than the cost of fuel for idling. The engine should not be shut down immediately after a hard run, however, but should be allowed to idle for a few minutes to allow engine temperatures to drop. Otherwise, a surge of hot coolant to the heads can cause damage. Also, turbocharger damage can occur if coolant oil and air flow are shut off too abruptly.

Warming Up the Engine

When starting, the engine should be warmed so that the coolant is in the recommended operating range before putting a load on the vehicle. This is recommended for diesel engines. For gasoline engines, check with a reputable dealer to find whether this warm-up period is necessary.

Choosing the Most Economical Speed

Every vehicle operator should know the most economical rpm range to achieve good fuel economy while delivering the desired horsepower. The best rpm range can be determined from performance curves, such as Figure 14.12, and from the fuel consumption map, such as Figure 14.13. If these curves describe the engine operated by a particular operator, that person should know that operating at 1700 rpm rather than 2300 rpm saves approximately 8% in fuel. Similarly, mechanical drive equipment should be operated in the highest gear practical. Since the economical operation of a vehicle fleet may enable the company to stay in business, saving this amount of fuel should be important to any operator.

Operating the Hydraulic System at the Right Speed

Care should be taken to operate the hydraulic system with enough power that the pumps do not stall. Stalling a hydraulic pump creates heat but does not get work done. Similarly, if operating a converter, the operator should downshift to get more power rather than allow the converter to stall.

Maintaining Recommended Coolant Temperatures

The operator should keep the coolant temperature in the range recommended by the manufacturers in order to achieve maximum fuel economy.

Fig. 14.12 Typical diesel performance curve. (Courtesy of Cummins Engine Company.)

800 1200 1600 2000 2400 2800 Engine speed (rpm)

Fig. 14.13 Fuel consumption map. (Courtesy of Cummins Engine Company.)

800 1200 1600 2000 2400 2800 Engine speed (rpm)

Fig. 14.13 Fuel consumption map. (Courtesy of Cummins Engine Company.)

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