Combustible future

Tier One suppliers discuss what technologies will be key to improving the efficiency of gasoline engines and meeting targets beyond 2020

Christopher Breitsameter - Continental’s vice-president of business development and strategy, powertrain division

We still see several technologies that can help further increase the thermodynamic efficiency of gasoline engines in order to push the efficiency significantly above 40%.

First and foremost, we see a continuous switch from port fuel injection to direct injection and downsizing. With our latest generation of direct-injection systems at 350bar and low-inertia turbochargers we can gain up to 13% fuel economy while significantly improving particle emissions in real driving.

Secondly, the variability of the drivetrain allows us to vary the opening and closing of inlet and outlet valves. The so-called Millerisation allows us to operate the engine in more efficient operating points, especially during part-load conditions, which further improves CO2.

Those key technologies and other smaller improvements will still lead to a significant improvement of efficiency until 2020. After that we expect a slowdown of development, so the annual efficiency gains, which used to be 3-4% per year, will slow down to 1%-1.5%.

We continue to work on ultra-low-inertia turbochargers, which allow a very fast speed-up for very high low-end torque. And we also see a trend towards efficient, simpler, variable turbine geometry turbochargers for gasoline.

So far this is a niche for high-performance cars, but with a simpler mechanism for changing the angle of the turbo blades this technology will be suitable for more mass-market vehicles.

We expect more engine platforms with multi-stage (two-stage/three-stage) turbocharging concepts that allow us to match, for example, a smaller turbo for the low-end torque fast response of the engine and a second, larger turbo for maximum power.

Through the introduction of low-voltage electrification (12V or 48V boardnets) there is significant potential for electrically assisted turbos or electric compressors which further improve low-end torque.

We have proven CO2 savings of up to 21% in real driving (urban cycle) and 13% in the NEDC test cycle. In addition to the significant CO2 saving we can further reduce particle emissions through peak shaving, by supporting the engine in peak load situations with additional torque from the electric motor.

There is a clear trend towards 350bar injection systems for gasoline engines. This is mainly to reduce the number of particles, while keeping the CO2 emissions at the same level. Going beyond 350bar increases the effort to generate the pressure and also leads to increased CO2 emissions. Additionally, in light of tighter regulation, other measures become more attractive in terms of effort versus benefit, for example gasoline particle filters.

We are heavily working on the introduction of multi-core chips to cope with the ever increasing software content and control functions to more precisely operate the engine. And we will use external data from the cloud and vehicle-to-vehicle data to further improve the operation strategy by predicting engine load, torque demand, and knowing the dynamic traffic conditions ahead.

In the end the OEM is looking at the cost-benefit ratio of all available technologies to further reduce emissions. We are constantly checking those ratios which will decide whether a technology will be introduced at all and, if it will be brought in, whether on a broad scale or rather for focused niche applications.

Some of these technologies for gasoline engines are water injection, homogeneous or stratified lean burn or closed-loop pressure control. One topic that is receiving continuous debate is the possible implementation of gasoline particulate filters.

There is no one-fits-all solution. It depends on the vehicle segment and the regional requirements. However, we consider a Millerised 350bar direct-injection turbocharged mild hybrid with 48V belt starter generator, three-way catalyst, gasoline particulate filter and connected energy management a very attractive, yet efficient and affordable, solution that is prepared for the regulations to come after 2020.

tags: May 2016 Borgwarner Bosch Continental Powertrain