Neil Pattison

Neil Pattison

Smaller engines, producing the same power as the larger engines they have replaced while using less energy and therefore generating lower exhaust emissions, are high up the priority list of every vehicle manufacturer. In truth it is part of a process that has been continuing for many years. In this interview, Matthew Beecham talked with Neil Pattison, Director of On Highway Business, Cummins Inc, about trends in diesel downsizing.

What signs are you seeing that serious diesel engine downsizing is on its way?

The challenge is always to get the engine package correct in terms of power and torque with the expected levels of durability, reliability, emissions and fuel economy for the market in which the vehicle operates.

Technology changes over the last 30 years or so including turbocharging, charge air cooling, electronic controls, and high pressure fuel systems have all increased the available hp per litre. For instance 14 litre naturally aspirated engines produced 185hp in the 1970’s, and we can now deliver this with our 2.8 litre ISF engine.  Despite this providing the opportunity to downsize, operators have taken advantage of the higher power and torque available to improve vehicle efficiencies. This has benefited their businesses with larger load capability and faster journey times.

More recently, there has been a move to downsize engines in diesel-electric hybrid installations.  For instance we have seen manufacturers moving from a 6 cylinder to 4 cylinder ISBe engine with the addition of an electric motor and battery pack.  Bus operators, where the stop start nature of operation is more suitable to hybrids, have seen fuel economy benefits of around 25% with no detrimental effect on performance.

What are the main strategies that engine manufacturers are taking to reduce light diesels’ fuel consumption?

The ever increasing cost of diesel makes fuel consumption is an emotive topic for operators.  As an independent manufacturer of engines, Cummins aims to add value to our customers. We are the only engine company to own all technologies from air handling to exhaust aftertreatment.  This allows us to better integrate turbochargers, fuel systems, combustion technology, electronic controls, engine filtration and exhaust aftertreatment and deliver the best level of fuel economy for each stage of emissions regulations. Managing this technology recipe using the latest components has seen our Euro 4 and Euro 5 products deliver excellent results and puts us in a good position for Euro 6.

Engines in the light CV market (M1, M2, N1 and N2) must go through a vehicle chassis certification rather than an engine dyno certification. In Europe we don’t really play in this area of the market, however we do in the US with the Ram and China with Foton.

How does the approach taken by heavy duty diesel makers differ?

Our main experience in Europe is with heavy duty diesels (M2, M3, N2, N3).  These go through engine dyno certification, so all development work has to be done on the engine in a test cell.  This means having close ties with our OEM customers is imperative to integrate the engine into their vehicle and ensure optimum performance and fuel economy.  Understanding how the engine works with transmissions, axles and other driveline components across a range of applications (e.g. truck, bus, and coach) is an important part of our engineering support capability to delivers the best possible result.

What are the main technical challenges in diesel downsizing? How different is it really to gasoline downsizing?

Downsizing is possible, however the challenge remains in getting the package correct in terms of power and torque with the expected levels of durability, reliability, emissions, fuel economy, noise etc. As a global organisation we look to tailor products to meet the specific market needs rather than a one size fits all.  For instance, in India, we see trucks with our 5.9 litre engines moving loads of 40 tonnes and above. The expectations of vehicle performance, speed, driveability etc. allow this, whereas in Europe it would be deemed unworkable and 11-15 litre engines would be used. 

The tougher nature of the duty cycles experienced in commercial vehicle use means that downsizing could affect the life of the equipment and/or its residual value.  So, it would have to be considered in response to a customer or market need.  We would ensure the engine and powertrain were fit for purpose in the application it was designed to operate in.

Diesels deliver much higher torque than gasoline engines, making them much more suitable for moving heavy loads or high volumes of passengers.  Torque capability is relative to cubic capacity, so the higher the displacement the higher the potential torque.  Any reduction in torque from using a smaller engine may reduce acceleration capability from start, and may need to be supplemented by an alternative power source, such as an electric motor in a hybrid installation.

How do you overcome the increased temperature and load requirements in a diesel engine?

Our years of installation expertise mean that no engine is installed unless it meets Cummins and the customers’ quality requirements. This protects their brand and ours.

Which are the components that pose the greatest problems?

As long as the engine specification meets the vehicle operational requirements and the correct maintenance practices are adhered to, including fuel and oil specs, then this is not an issue.

How likely it is that downsizing will affect your volumes? If everybody moves from V6 to I4s and from I4s to I3s, doesn’t that mean less business for engine parts manufacturers?

Cummins has a range of diesel engines for commercial vehicle use from 2.8 to 15 litres, and larger products for industrial use up to 95 litres.  We pride ourselves on having the flexibility to provide the right engine for each customer need, based on their operational requirements. 

Due to improvements in manufacturing techniques and quality measurement, engines have become much more reliable over the last 20 years or so.  The challenge for parts manufacturers to increase business is not a new phenomenon, and will continue to be a challenge moving forward.