In 2019, Cummins celebrates 100 years of diesel engine production, during which it has produced more than one million engines for agricultural applications. Cummins application engineer and technical specialist Ryan Wainwright-Fisher reveals what can be done to maintain economy and performance of tractor diesel engines. Simon Henley reports.
When it comes to describing how a diesel engine works, the terminology ‘induction-compression-ignition-exhaust’ remains as relevant today as it did when the internal combustion engine was invented 140 years ago.
What has changed in the past 25 years is that electronic technology now plays an increasingly important role in modern engine development, as engine manu- facturers strive to gain greater power, density and economy from smaller engines which comply with ever more stringent emission regulations.
The requirements for reliably producing power from a diesel engine can essentially be attributed to the efficient delivery of fuel and the ability of the engine to process that fuel.
Without the correctly metered ratio of fuel and air, or the compression to generate enough heat to burn the fuel, the engine will not run efficiently. This has not changed.
However, there is now another factor which can affect engine performance. In modern tractors, diesel engines are not only required to produce power efficiently, they are also required to emit lower emissions from their exhaust stacks. This factor has presented an interesting challenge to engine manufacturers, as Ryan Wainwright-Fisher explains.
“We use sensors to monitor fuel and air going into an engine, and the exhaust coming out. By controlling what goes on in the middle, we can stipulate what the engine produces, both in terms of power and exhaust emissions.
“It is how we control what is going on inside the engine which represents one of the biggest advances in recent years. However, what has become more crucial than ever is the necessity for following the original equipment manufacturer [OEM] service guidelines to maintain engine health.”
Regular maintenance is key to maximising fuel economy and engine performance, and in the modern diesel engine, oil is the key element for the protection of the engine.
Diesel engines use high-detergent oil. The detergent is formulated to act as a cleaning agent in the engine to reduce sludge, varnish, and oxidation build-up on the pistons, rings, valve stems and seals. Oil formulated with the optimal additives will hold contaminants in suspension until they are removed by the oil filtration system or during an oil change.
Oil has always been essential for lubrication. However, it has also become a key component in the service life of engine emission systems.
The latest Stage 4 and upcoming Stage 5 engines equipped with diesel particulate filters (DPF) require a low-SAPS (sulphated ash, phosphorus, sulphur) content.
Oils with a high SAPS content will block DPF filters on modern diesels, reducing the time between regeneration cycles and shortening the DPF service life. Modern low-SAPS oils are specifically formulated by oil companies to meet the requirements of engine manufacturers, such as Cummins, and the importance of using the correct oil for a specific engine has never been greater.
Mr Wainwright-Fisher says: “Where engines are concerned, you should always use a high-quality OEM oil filter. On Cummins engines, always use Cummins genuine parts and change the oil and filter together.
“It is the same for fuel and air filters. Modern turbocharged diesel engines with high-pressure fuel systems require high-micron fuel filters and a high volume of clean air to operate effectively.
“Removing the air filter and tapp- ing the dust out on the tyre is not good practice. Air filters should be maintained according to the manuf- acturer’s directions, which may mean cleaning them.
“Filters which do not allow cleaning [check the manufacturer’s guidelines] should never be blown out, as this can cause damage to the filter, resulting in damage to high tolerance parts within the engine.”
So what else can be done to help improve fuel consumption? According to Mr Wainwright-Fisher, another simple answer is to switch off the engine.
He says: “Statistically, tractors spend a great deal of time standing idle, with engines left ticking over. This not only wastes fuel, but on engines equipped with a DPF, because the filter is working harder, it shortens the intervals between regenerations.
”Another method cited for saving fuel is to avoid using full-throttle and let technology do the work. Aggressive driving increases fuel consumption, reduces brake life and increases tyre wear.
Most modern tractors are equipped with transmissions which offer automatic shifting with speed-matching, as well as Eco and Field modes, to optimise the balance between performance and fuel economy.
This technology has been developed by OEMs to help farmers get the most out of their tractors and equipment. Furthermore, it is designed to work in conjunction with other technologies, such as GPS co-ordination and field mapping.
By using field mapping, for example, the operator will be shown the most fuel-efficient route for ploughing or harvesting a field. Using a combination of guidance and modern transmission technology, fuel savings on even the largest tractors can be quite significant.
Another important factor is tyre pressures. In farming, there can be a trade-off between tyre pressures and fuel consumption, when considerations such as wheel slip, tractive effort and compaction are taken into account.
Remember, low tyre pressures require more fuel, because more effort is required to move the tractor.
However, when operating in a muddy environment, low tyre pressures help increase traction and reduce wheel slip. Many tractors are now fitted with traction systems, which help generate traction by minimising wheel slip. Using these tools not only optimises in-field performance, they help maximise fuel efficiency.
Ballast is another important factor which should not be overlooked. The minimal ballast requirement necessitates applying enough weight for the tractor to pull the implement. The slower the pull, the more power required and the heavier the tractor needs to be.
Using a heavily ballasted tractor for light applications or road work simply wastes fuel. The ballast should be removed or a lighter tractor used instead. The same applies to filling up with fuel.
Filling the tank to the brim when half a tank will do adds unnecessary weight to the tractor. A 160hp tractor with a 400-litre fuel tank is carrying 332kg of diesel with a full tank. That is the equivalent of having three 17-stone people in the cab with the driver.Another commonly practised habit which wastes fuel is unnecessarily using an oversized tractor. How many times have you seen a 200hp tractor rowing up hay with a two-row tedder, or a 300hp tractor pulling a 12-tonne grain trailer?
Mr Wainwright-Fisher says: “Our recommendation for farmers would be to monitor their driving style and fuel usage over a monthly period.
“This will enable them to identify when heavier fuel consumption occurs and make changes where necessary – just switching off the engine will save most people some money.”