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 Derk Geurts about trends in diesel engine downsizing. Derk is Delphi’s chief engineer for diesel common rail systems (light duty and passenger cars).
just-auto: What signs is Delphi seeing that serious diesel engine downsizing is on its way?
Derk Geurts: It is already happening in every market sector. Even the Mercedes S-class is now offered with a four-cylinder engine. Mid-sized cars are increasingly available with a 1.6-litre diesel as an alternative to a 2.0-litre, and the VW Polo offers a 1.2-litre three-cylinder alternative to the conventional four-cylinder 1.4 or 1.6 engine. These are not budget-price engines; they are actually some of the most technically sophisticated on the market.
For high-end applications our direct-acting piezo system is allowing a big step forward in combustion efficiency, while for volume applications the ability of our solenoid system to provide servo-piezo performance at a more attractive price is also creating strong interest. The majority of our customers are not using these systems to only provide increased performance. They are using them to provide smaller, more efficient engines with the same level of performance and refinement as their larger, heavier predecessors.
What are the main strategies that engine manufacturers are taking to reduce light diesels' fuel consumption?
They are reducing mass, friction and other parasitic losses in every engine system as well as increasing the combustion efficiency. Increased efficiency leads to reductions in the engine capacity, but the biggest step is reducing the number of cylinders. For me, this is the true meaning of ‘downsizing’. As a technology supplier, we have to help the vehicle manufacturers reduce the number of cylinders without their customers noticing any reduction in performance, driveability or refinement.
We have also analysed the downsizing potential of our fuel injection system. For example, our single cylinder high-pressure fuel pump runs at engine speed, can deliver up to 2000 bar and is one of the lightest and most efficient on the market. Supplied by our brushless electric low pressure fuel pump it provides the exact amount of fuel required, unlike more wasteful fixed-delivery systems that continually return surplus fuel to the tank. The Delphi variable controlled brushless pump can lead to a CO2 reduction at the vehicle level of 2 to 3 percent without any trade-off in emission performance.
How does the approach taken by heavy duty diesel makers differ?
There is a fundamental difference in their duty cycle. Light duty engines spend longer operating at low loads, idling and warming up after cold starts. Heavy duty diesels run for longer at high speeds and loads so they are, effectively, already downsized to give the best possible fuel economy with adequate load-carrying performance.
Within Delphi, there is a two-way transfer of technology between our light and heavy duty engineering teams as we constantly look for better ways to meet the future needs of the market. For example, our heavy duty team has considerable experience with very high fuel pressures and this is now helping to advance our light-duty systems. The heavy-duty team has called upon the light-duty team’s expertise in common rail.
What are the main technical challenges in diesel downsizing?
Cost must be kept down while delivering the required fuel economy with satisfactory refinement, adequate low-speed torque and meeting NOx emission targets. For diesel, NOx is a particular challenge and one that Delphi is addressing in a number of ways including the development of advanced SCR systems.
We are also tackling emissions and NVH at source. As an example of this, Delphi’s servo-solenoid diesel injectors help by offering servo-piezo levels of performance at solenoid prices. They are used on the new VW 1.2-litre three-cylinder diesel engine, which in the Polo has a stunning CO2 performance of 87 g/km.
To help maintain the initial performance and refinement throughout the engine’s life, Delphi was the first to introduce closed loop control for diesels and we now have it as a standard feature on all our systems along with individual injector characterisation.
Another frequent development challenge with downsized engines is the risk of design changes late in the programme, in order to meet opposing targets. Our model-based engine control software makes recalibration of the system much quicker and simpler after such a change and helps to pull back the time lost.
How different is it really to gasoline downsizing?
The issues are similar but the maximum boost used on a downsized gasoline engine is limited by knock, hence the trend towards direct injection to improve knock-resistance. Delphi has recently introduced a gasoline DI system specifically to help our customers move to smaller, more efficient engines.
By using three-way catalysts, gasoline development has been less restricted by emissions than has diesel, until now. We can see some convergence in diesel and gasoline strategies as both now use direct injection, turbocharging and cylinder reduction to provide high power density and reduced losses with low CO2 emissions. Delphi supports both engine types and each area of engineering benefits from the expertise of the other.
How likely is it that downsizing will affect your volumes?
The downsizing trend will not adversely impact total engine volumes. In fact, this trends’ contribution to CO2 reduction and vehicle efficiency is such that it is extending the viable life of ICE in transportation beyond previously thought limitations. Delphi’s demonstrated technology in downsized engines, for example with our Multec Solenoid Common Rail systems in small, highly efficient diesel engines, has shown why Delphi is well positioned to benefit from this trend and increase volumes.
If everybody moves from V6 to I4s and from I4s to I3s, doesn't that mean less business for engine parts manufacturers?
By mastering the technical challenges with affordable solutions, we are expanding our portfolio and winning new customers. Diesels are more amenable to downsizing than gasoline, so we see their market share increasing, again having a positive effect on our volumes. As NOx control and aftertreatment strategies improve, it is likely that this trend will accelerate. Overall, we are not concerned that downsizing will have a negative effect on our volumes. On the contrary, it makes our strategy of high-performance with simplicity even more attractive.