Almost all of the low-hanging fruit for improving fuel economy and reducing emissions has been plucked. To keep hitting increasingly stringent standards, engineers are faced with identifying solutions that may be completely innovative or unconventional – to continue the analogy, they need to target the fruit higher up the tree and harder to reach.
However, most are confident that the internal combustion engine (ICE) will retain its position as the most popular engine architecture in the automotive industry over the next decade. This is thanks to the help of a number of new technologies that could soon find their way to market.
The middle ground
“There is considerable development on-going in engines and powertrain technology in general,” Dean Tomazic, Executive Vice President and Chief Technology Officer, FEV North America, told Megatrends. The supplier has long specialised in the design and development of powertrain components and concepts, and has a number of technologies currently in development that will soon be launched.
One of these, said Tomazic, is variable compression ratio (VCR). “Today’s combustion engines have a dedicated compression ratio,” he explained. “The engine is under low load operation when driving through cities or busy traffic, making it suitable for high compression ratios, because the higher the compression ratio the better the thermal efficiency. But when you approach high loads, then knocking becomes an issue. This can be mitigated by spark retardation or enrichment, but neither is beneficial for fuel consumption.”
Tomazic said there needs to be a “reasonable middle ground” in terms of compression ratio selection, whereby fuel efficiency and peak torque requirements are both met.
FEV has been working on VCR prototypes for more than two decades. Tomazic said that the technology “allows you to change the compression ratio depending on where you are in your operating map as a function of speed and load, providing far more flexibility.” He is confident that FEV’s latest solution “boasts the best of both worlds – good fuel consumption at low loads, and a lower compression ratio at higher loads, lowering the need for spark retardation or enrichment.”
The VCR technology can be used in both diesel and gasoline engines, but the primary market would be the latter. This, said Tomazic, is due to the fact that “the biggest bang for your buck is on the gasoline side.” There are also numerous advantages exclusive to diesels, he added, but the gasoline market is the target for VCR.
The diversification of technologies will be huge. It’s a trend that will be visible across the vehicle, including the powertrain
Time is ripe
So how does it work, and why hasn’t it been done before? The VCR mechanism is incorporated into the connecting rod, which is in turn connected to the piston through the wrist pin to the crankshaft – a completely new connecting rod design. “The beauty of the design is that it is a two-step system, so it can run at either high or low compression ratio.” The quick transitional period when switching between the ratios is a feat that is particularly important to downsized and turbocharged gasoline engines.
“When you think about the acceleration process in these engines, there is a time requirement to build up sufficient boost pressure,” he noted. “In most applications this takes more time than switching between compression ratios.” He added that the design of the system allows gas and mass forces to move the piston relative to the connecting rod. It also includes a shuttle valve that is located at the lower end of the connecting rod, which “tells the connecting rod when it needs to shift from high to low compression ratios or vice versa. It’s a very simple mechanism that only needs a small electric motor to power it.”
Tomazic is confident that the system will help FEV’s customers achieve essential gains in fuel economy, as well as emissions reductions. “There are other potential benefits,” he added. “For example, we can also increase the low end torque of the system depending on how much we are willing to compromise on fuel consumption. This means that we can drastically increase the power output of the engine.”
Given the numerous benefits, it might be difficult to understand why VCR has not already been brought to market – and Tomazic concurs. “The answer lies in the fact that fuel has been cheap, particularly across the US. And from a regulatory perspective, there hasn’t yet been any need to introduce VCR. But both those factors are changing, and the low-hanging fruit for CO2 reduction and fuel efficiency improvement has gone, but we still have to comply with much more stringent requirements. This means that the time is ripe for VCR,” he remarked.
FEV has a number of customers that are already testing its VCR technology, incorporating it into their vehicles and running fleets on public roads for validation. The technology could therefore be introduced as early as 2017.
The vast array
VCR isn’t the only technology that FEV is examining. The company is also looking at new variable valve train technology that Tomazic says could offer many advantages in combination with conventional direct injection (DI) systems, including lowering the exhaust gas temperatures. “This could allow us to apply variable geometry turbines, giving us even more flexibility in terms of low end torque and peak power.”
Tomazic also highlighted developments in exhaust gas recirculation (EGR) technology. “This will play a big role because it allows us to de-throttle the engine and increase thermal efficiency,” he explained. “This compliments the benefits that we can get from using VCR.”
Other areas of interest and development include minimising thermal losses,friction reduction – as reducing parasitic losses can lead to big improvements in fuel efficiency – and electrification. “We are working heavily on 12-volt systems as well as 48-volt applications. With the latter, e-chargers can be incorporated into the system to ramp up vehicle performance. We can even run the air conditioning off the system, which could significantly improve fuel consumption and decrease CO2 emissions.”
While he thinks the low-hanging fruit has been plucked, Tomazic is confident that there is a wide array of technologies yet to reach the market. “The key is to pick the right combination, because they have to complement each other to get the best outcome,” he noted.
Looking ahead to 2025 and beyond, Tomazic noted that the connected car is certain to change the way that the powertrain works. With different vehicle requirements, and varying consumer preferences, “The diversification of technologies will be huge. It’s a trend that will be visible across the vehicle, including the powertrain.”
This article appeared in the Q3 2016 issue of Automotive Megatrends Magazine. Follow this link to download the full issue.