Let's start the discussion by looking at the use of engine torque and rated power at maximum r/min. These are key issues and in this regard, it must be remembered that torque characteristics of diesel engines differ considerably between truck makes - and even between engine designs from a common engine manufacturer.

It is management's task to know the shapes of the torque curves of diesel engines within a fleet and to set boundaries of how engine-effort must be managed within a specific torque curve. Most important is that this knowledge must then be imparted to drivers in an easy to understandable way which allows them to drive to this formula.

Ultimate benefits are derived from measuring a driver's on-road observance of prescribed engine performance parameters and sharing the knowledge of success or deviation with the driver. The good news is that the modern electronically managed diesel engine makes this task easy as the information can be downloaded directly from the engine's electronic control module. Use of engine torque can also be tracked from tachographs or on-board computers.

The above point is most important as success comes not only from telling a driver what to do with engine power but also why he must adhere to specific parameters and how this works for him on the road. Motivational success then comes from sharing his achievement in reaching these targets. Driving is about attitude and motivation as much as it is about the skills of controlling engine speed and torque on changing grades and road conditions.

An example of where success can be measured and shared lies in fuel consumption. Good fuel consumption is an output of proper, efficient torque management and a driver's task is to get the most out one litre of fuel within a specific time frame for maximum payload.

Engine speed & retardation
Stopping a heavy truck is just as much an art as is managing forward motion. All trucks from around 6 tons gross vehicle mass are fitted with diesel engines incorporating auxiliary retardation devices. These devices range from simple exhaust pipe engine brakes to complex cylinder head valve systems developing as much kilowatt (kW) power in retardation as the engine will originate at full throttle and at maximum r/min.

Drivers and their supervisors must understand how kinetic energy will be managed. It is costly and dangerous to allow the full kW of kinetic energy of truck rolling forces to be absorbed by the foundation brakes in the drums and shoes.

While fuel economy is derived from holding an engine in the 'sweet spot' of a torque curve - usually at lower r/min - retardation power in an engine is developed at maximum rated engine speeds. It is for this reason that a driver must be allowed to reach maximum engine speed under given circumstances and fleet managers must understand why a driver is doing this. It is to manage the power train on a down grade and stop foundation brakes from over-heating.

Everyone's nightmare 
Diesel engines do not take kindly to over-revving - running an engine well beyond maximum rated engine speed. This is the reason many fleet managers discipline drivers who approach maximum engine speed and why many drivers struggle to control kinetic energy forces with resulting high brake repair costs.

An over-revved diesel engine shows easily discernible damage. The problem is that the first time this occurs, it can be a surprise for both a driver and his supervisor. What must be realised is that over-revving is an operational hazard and therefore costly diesel engine damage will not be absorbed by any truck or engine manufacturer.

The cause of an engine over-rev situation has to be understood by all parties involved. This means comprehending the losses incurred in terms of downtime and repair expenses. It is obvious therefore that over-rev prevention and managing kinetic energy without placing an engine at risk should be a priority.

Not too cold nor too hot 
Drivers must also be aware of variances in engine temperature as this is a driving discipline that can forestall major problems. While modern electronically managed diesel engines are programmed with shutdown features to protect an engine against overheating, the majority of trucks on our roads depend solely on consistent driver discipline in checking vehicle instruments to prevent engine damage. Sure, some engines are equipped with audible warning devices such as buzzers but does your driver know what audible warning signals are fitted to his truck?

Just as important in preventing engine wear is for the driver to ensure the engine does not run too cool. Both drivers and their supervisors must understand the consequences of engines that run cold due to thermostatic control failure. A diesel engine provides exceptional life when run at consistent temperatures - neither too cold nor too hot.

Air filtration restriction indicators 
All modern diesel engines are fitted with air cleaner restriction indicators. This useful item indicates when an air cleaner element requires replacement - either via a warning light in an instrument cluster or a small vacuum-operated flag device on the clean-air side of the air cleaner element.

Drivers must understand the importance of the information provided by an air restriction indicator which, quite simply, means it is time to replace an air cleaner element. The consequences of not replacing an element are loss of engine power, over-fueling of the engine and excessive black exhaust smoke. Drivers and fleet managers who share this information and replace air cleaner elements at the right time will reduce engine wear, fuel consumption and operating costs.

Lube checks and topping up 
Drivers have direct contact with lubrication systems in terms of inspecting and checking engine oil levels and topping up. Diesel engine oil consumption will be at around 0,5% of total fuel used - 5 litres of oil for every 1000 litres of fuel. Management must train drivers in the following:

• Correct brand and viscosity rating for topping up. Drivers who top up with poor quality lubricants do not comprehend the ratio of the price and quality of oil to the costs of poor lubrication.
• How to read dipstick levels and avoid over-filling.
• Only to check an engine when it is cold before start-up. If a big diesel engine is started before dipstick checks, a driver may have to wait as much as 15 minutes for the oil that has collected in the top of the engine to drain back into the sump. This can amount to as much as 6 litres of oil and this is where over-filling occurs because levels on dipsticks do not indicate what may be in oil galleries in the top of the motor.
• Only to use of clean materials when checking dipsticks. A dirty rag from the floor can introduce grinding paste directly into an engine

Cooling systems 
This is another driver check that must only be conducted on a cold engine. A well-maintained cooling system functions at high pressure when it reaches engine-operating temperature> Besides that, it is dangerous to check and top up hot radiators and expansion/header tanks.

•  Drivers must understand the importance of pressure caps and how to read expansion/header tanks and not overfill the system.
• Cooling systems that require excessive topping up indicate serious technical problems. Drivers must be trained to recognise this and report cooling system deficiencies.

Start up and shutdown 
There should be no difference between a truck driver and an aircraft pilot in terms of start up check procedures. Fleet managers should set the standards on what they want to be checked and how they will react to a driver's report back on his daily start up checklist.

The first 10 minutes of a cold start is the most critical period for engine wear. Electronically managed engines can be programmed to idle for the first three minutes after starting, regardless of how a driver treats the accelerator. This at least protects a cold engine from being revved when cold.

TECHNOLOGICAL GIANTS  Barloworld's Caterpillar (above) and Cummins' ISX engines (right) are both being fitted to the Freightliner Argosy range. Such engines are giants in terms of technology and sophistication and it is only the very naïve operator who will expect an untrained driver to get the best out of them. Managers and drivers must work closely in understanding all aspects of the engines under their control.

Leaking air brake systems are a common cause of engine wear in heavy diesel powered trucks. The reason is that drivers rev up cold engines to charge up empty air pressure reservoirs in brake circuits - the rear axle spring brakes will not release until the system is sufficiently pressurised.

Drivers and fleet managers must realise that the consequences of leaking air brake circuits extend far beyond loading bays. Drivers will fall into a habit of letting an engine idle all day to keep air brake reservoirs charged - this further aggravates engine wear.

Drivers have direct contact with lubrication systems when checking oil levels. Are they trained in the task?

The enemies of diesel engine life are excessive idling and revving at cold start up. These two items must be monitored by a driver and his managers and ways found to combat any situation that causes these problems.

Similarly, engine shutdown procedures present an opportunity to take charge of incidents that occurred during operating time which may require attention. The objective is to report an engine technical fault before it turns into an on-road failure.

Understanding instrumentation 
Modern truck instrumentation and engine controls offer information that assist drivers and managers to extract the very best in terms of engine performance and road safety. An engine that operates on three stages of retardation - 2, 4 or 6 cylinders - provides a multi-stage control switch for the driver in the cab. A driver and his supervisors must know the reasons for staged retardation and circumstances under which these stages can safely be used.

Warning lights often have dual functions. Supervisors should make sample checks of a driver's knowledge of the instrument panel warning systems and how these instruments can help a driver and prevent engine failures.

In summary, managers and drivers have to work closer in understanding the workings, characteristics and all other aspects of the engines under their control. Do this and you will take a quantum leap forward in achieving maximum economy and productivity from your vehicles.