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05 March 2024
23 June 2020
FEV on powertrain trends
Meeting tomorrow's challenges through innovative engineering
Prior to the COVID-19 pandemic lockdown phase, Infineum Industry Liaison Advisor, Andy Ritchie, met in February with a group of engineering leaders from FEV to discuss emerging trends for the internal combustion engine and broader powertrain development, such as the progress being made in electrification. Understanding the changes in these areas is critical as industry strives to meet the challenges of providing consumers with appealing products while also meeting more stringent efficiency, air quality, and greenhouse gas regulations.
FEV is a leading independent international service provider of vehicle and powertrain development for hardware and software. The range of competencies includes the development and testing of innovative solutions up to series production and all related consulting services. The range of services for vehicle development includes the design of body and chassis, including the fine tuning of overall vehicle attributes such as driving behaviour and NVH. FEV also develops innovative lighting systems and solutions for autonomous driving and connectivity. The electrification activities of powertrains cover powerful battery systems, e-machines and inverters. Additionally, FEV develops highly efficient gasoline and diesel engines, transmissions, EDUs, and fuel cell systems, and facilitates their integration into vehicles suitable for homologation. Alternative fuels are a further area of development. The service portfolio is completed by tailor-made test benches and measurement technology, as well as software solutions that allow efficient transfer of the essential development steps of the above-mentioned developments, from the road to the test bench or simulation. The FEV Group is growing continuously and currently employs 6,700 highly qualified specialists in customer-oriented development centres at more than 40 locations on five continents.
With the automotive industry focused on reducing fuel consumption and tailpipe emissions, Infineum was keen to understand what FEV sees as the key trends and drivers for future hardware innovation.
Passenger car internal combustion engine
With the wide market adoption of full battery electric vehicles still some way into the future for the US-market, keeping pace with the changes in internal combustion engine (ICE) design is essential to ensure fuels and lubricants of the future enable their optimal performance.
Dean Tomazic, FEV North America Executive Vice President and Chief Technical Officer, explains some of the ICE options available to OEMs as they strive to meet tightening regulations. “As OEMs work on so-called engine ‘rightsizing’, the combination of turbocharging with gasoline direct injection (DI) has become a mainstream technology package, and we have seen a continuously increasing market share of turbo DI engines worldwide. OEMs do have other alternatives, such as the Atkinson Cycle - a very cost-effective, naturally aspirated, high compression ratio engine concept that can achieve diesel-like brake thermal efficiency. However, its reduced specific power output means this concept is best suited to hybrids or applications that do not require high specific power and torque. The other option we see is the Miller Concept where, to mitigate the loss of higher peak power, switchable cam profiles have been introduced to achieve optimised fuel efficiency at part load and high specific power output.”
Within these ICE variants, Dean runs through some of the advanced technologies and combustion system improvements OEMs are employing as they work to improve fuel economy.
Dean Tomazic, FEV North America Executive Vice President and Chief Technical Officer Infineum International Limited
Applying either a fixed or a rolling type of cylinder deactivation, the brake thermal efficiency can be improved by increasing the load level of the remaining active cylinders.
Applications can vary from three to typically eight cylinder engines and will continue to expand. In addition to that, the use of a variable compression ratio mechanism allowing compression ratio adjustment based on the operating point of the engine to enhance combustion efficiency has been a desire of engine development engineers for many decades. With the development of 2-step as well as continuously variable systems, which, meanwhile have made it into production, one can achieve the best of both worlds; improved fuel consumption at part load and increased specific power output at high loads, up to full load. Due to the significant advantages, we will see more variable compression ratio applications in the future. Furthermore, the reduction of parasitic losses continues to play a major role. Design features such as eccentric crank and wrist pin designs, coatings, form honing, optimised FEAD designs, and others continue to reduce friction within the engine.
Also, electrification, using on demand 48 volt coolant pumps or AC compressors, can contribute in this case. Other measures such as the rapid warm up of engine coolant as well as engine and transmission oil help lowering fuel consumption. In that context, we also see more and more low viscosity lubes, which contribute to the reduction of friction in the engine. With respect to combustion system development, further improvements in port, as well as combustion chamber design in concert with fuel injection system optimisation, as well as associated controls, will continue to support improving fuel consumption. In addition to that, technologies such as cooled EGR and water injection can further help improve fuel consumption and support the potential future requirement of a flat Lambda one map, avoiding any enrichment at high loads. There, for stoichiometric, as well as the extreme lean burn combustion systems, the utilisation of a pre-chamber could gain in importance.
With strict tailpipe emissions regulations going live in Europe and India in 2020, OEMs have been introducing and optimising aftertreatment systems to ensure compliance. And, as the trend to lower and lower emissions continues, Dean says he expects gasoline particulate filters (GPF) to be required worldwide in the future. However, in addition to hardware and system modifications, he is keen to point out the contribution that fuels can make.
Dean Tomazic, FEV North America Executive Vice President and Chief Technical Officer Infineum International Limited
Fuels make a massive contribution to regulated emissions and CO2. Increased gasoline octane ratings as demanded by the industry in the US, could already have a significant impact on reducing CO2 emissions. Beyond that, E-fuels, and particularly hydrogen, not only for fuel cell applications, but also combustion engines, once available in higher quantities and with a robust supply infrastructure, can become a major contributor.
However, explains Troy Kraemer, FEV North America Director of Engineering for Gasoline Engines, in some cases the changes introduced to improve fuel economy and reduce emissions can have unforeseen consequences.
Troy Kraemer, FEV North America Director of Engineering for Gasoline Engines Infineum International Limited
Over a decade, the average passenger car engine sizes have come from four litres in displacement, naturally aspirated, port injected, with a four speed transmission, down to two litres in displacement, turbocharged, direct injected, with a 10 speed transmission.
This results in today's engines running at lower engine speeds and higher engine loads, most of the time. This combination has led to an uncontrollable phenomenon called low-speed pre-ignition, often abbreviated as LSPI.
LSPI is an uncontrolled combustion which occurs before spark plug ignition, which causes damaging pressures inside the combustion chamber, eventually leading to damaged pistons and even engine failure.
The automotive, fuels and lubricant industries are looking at ways to control LSPI, but Troy says a fine balance is needed here to ensure emissions and efficiency performance are not also compromised.
Troy Kraemer, FEV North America Director of Engineering for Gasoline Engines Infineum International Limited
Engine manufacturers can increase the piston strength to better handle LSPI events, but such a design to withstand LSPI through the life of an engine would result in a piston that is very heavy leading to reduced engine efficiency and higher component costs.
Additionally, engine manufacturers can increase the amount of fueling in the induction stroke to act as a cooling mechanism to reduce the temperatures in the combustion chamber, avoiding the conditions where LSPI occurs.
Again, this leads to increased fuel consumption and emissions.
Part of industry efforts are focused on gaining a better understanding of deposit build up inside the combustion chamber, which, as Troy explains, can also contribute to conditions leading to LSPI.
Troy Kraemer, FEV North America Director of Engineering for Gasoline Engines Infineum International Limited
Deposit buildup inside the combustion chamber on the piston face, combustion chamber walls, and valve faces, can lead to increased temperatures in the compression phase, setting conditions for an LSPI event.
These deposit build ups can be alleviated with fuel and lubrication detergent additives, but these additives are also a contributor to the fuel and oil being able to mix together, also leading to LSPI events. Therefore, the engine manufacturers and fuel and lubrication industry are working together to better understand and prevent LSPI. One area of focus is in the additives to prevent oil and fuel combination during the induction stroke, whilst still providing protection against deposit buildup in the combustion chambers. Another area of focus is in the operating conditions of the engines to help prevent in-cylinder conditions that create deposit build up, excessive air induction temperatures, better air-fuel mixtures, and reduced enrichment.
Despite the challenges of introducing new technologies or combustion strategies, engine manufacturers continue to look for ways to increase the fuel efficiency and reduce emissions from spark ignited engines. These are, Troy suggests, the key drivers behind pre-chamber combustion systems currently being investigated.
“The efficiency of the engine is strongly influenced by the quality and duration of the combustion process – an area OEMs are looking at using a pre-chamber to improve,” he confirms. “This miniature combustion chamber, connected to the main combustion chamber and surrounding the spark plug, has a number of very small holes, which provide multiple ignition points for the air-fuel mixture. This increases the amount of total ignition energy in the main combustion chamber, allowing very lean mixtures to ignite and rapidly burn and thus improving fuel economy. However,” he continues, “just as a pre-chamber combustion system has benefits, it also presents some challenges in terms of its incorporation into a traditional engine and also the aftertreatment conditions for lean-burn combustion systems it brings about, which are difficult and expensive to overcome.”
Transmissions enhancements
It’s not solely under the hood that OEMs are looking for contributions to improved fuel economy. Kiran Govindswamy, FEV North America Vice President of Powertrain and Vehicle Engineering and NVH, says there are on-going enhancements in the transmission and driveline world, too.
Kiran Govindswamy, FEV North America Vice President of Powertrain and Vehicle Engineering and NVH Infineum International Limited
Since the transmission is physically located between the engine and the rest of the driveline, there are fairly clear engine-driven challenges that influence transmission development. Specifically, the “engine-out torsionals” or speed fluctuations need to be managed so that there are no durability or noise and vibration concerns related to the transmission. This item becomes important as technologies such as boosted, direct-injected gasoline engines and cylinder deactivation become more common.
In addition, as OEMs work to gain efficiency improvements from the transmission system, Kiran sees a number of both 'direct' and 'indirect' improvements.
“Direct efficiency improvements include enhancements that can be measured at the component level and here the first order of business is to minimise parasitic losses within the transmission. This could be achieved in a number of ways such as minimising drag from open clutches, lowering churning losses, using low drag seals and high efficiency bearings. In addition, optimising the fluid fill level and its viscosity are also very important. However, viscosity reductions must be carefully balanced with concerns related to gear durability and leakage in the valvebody. Indirect efficiency improvements are those that would allow the engine to operate in a better 'sweet spot' from a brake-specific fuel consumption (BSFC) perspective. This requires a large ratio spread with small ratio steps within the transmission, so the drivability, shift quality and overall powertrain efficiency can be collectively optimised.”
Today, various degrees of hybridisation span the space between ICE powered vehicles and electric vehicles. Looking out to the future, Kiran sees a growing diversity in the transmission landscape, which will include non-electrified and hybrid transmissions with multiple architectures including automated manual transmissions (AMT), dual clutch transmissions (DCT), planetary automatic transmissions, continuously variable transmissions (CVT), and dedicated hybrid transmissions (DHT).
Kiran Govindswamy, FEV North America Vice President of Powertrain and Vehicle Engineering and NVH Infineum International Limited
The split between transmission types and the degree of hybridisation over the next decade will continue to be different in different parts of the world. As an example, in the US we expect full hybrids to be in the 18% range at the end of the decade. This will include both HEV and PHEV applications. It is important however, to note that these applications would be split between modular hybrid transmissions, DHT, and P4 applications. P4 applications will provide electric all wheel drive (AWD) and “through-the-road” hybrid functionality. Electric drive units developed for P4 applications can also be adapted for the electric vehicle market, which will include battery electric vehicles as well as fuel cell electric vehicles.
Development of transmission fluids with appropriate dielectric properties that meet the needs of lubrication, heat transfer, shift quality, durability, and efficiency will continue to be very important, especially in the presence of high motor and shaft speeds.
Electric vehicle technology
How fast and how far battery electric vehicles (BEV) will penetrate the light-duty vehicle market is a topic of much debate. Though the rate of EV sales in increasing steadily, plugin electrics accounted for less than 3% of sales in 2019 while 9 of the top 20 best selling cars were SUVs and pickups.
However, FEV North America Director of E-Mobility, Harsha Nanjundaswamy points out that since BEVs have the most efficient powertrains with the lowest GHG emissions they are being pursued by many OEMs as a mainstream alternative to conventional internal combustion engines. But, it is essential here, he says, that they address customer demands for extended range and faster charging.
Harsha Nanjundaswamy, FEV North America Director of E-Mobility Infineum International Limited
As the demand for longer range vehicles with fast charge capability continues to grow, clearly the emphasis is on energy loss mitigation, smart energy management, improved energy recuperation and higher onboard energy storage without a compromise on weight. Thermal management is at the centre stage of all known measures. This includes technologies such as novel permanent magnet synchronous machines, silicon carbide power inverters, and high specific energy battery packs. If you take a closer look at electric drive units, many new strategies are being deployed such as pre-conditioning to enhance the cold start performance, direct cooling of stator windings and direct cooling of the rotor shaft and rotor surfaces to reduce copper loss and increase peak and continuous performance while making the electric drive units more efficient.
Harsha goes on to explain how electric vehicle OEMs are busy evaluating the benefits of design trends, such as sharing the vehicle chassis structure for battery pack rigidity, and other measures including direct cooling.
Harsha Nanjundaswamy, FEV North America Director of E-Mobility Infineum International Limited
These measures seem to offer many advantages, such as reduced weight, compactness and improved effectiveness of cell temperature management, which enables a safer way to control the high current charge and discharge rates. In addition, harnessing the synergy of thermal management between the HVAC, battery pack and electric drive unit are becoming new avenues to implement novel thermal management schemes to minimise all energy waste by maximising the use of onboard energy for propulsion
Commercial vehicle developments
In the commercial vehicle world, hardware development is typically driven by new regulatory requirements, customer expectations or market competitiveness. Michael Franke, FEV North America Vice President Diesel and Commercial Powertrains, says in the US, the combination of GHG Phase 2 regulations and a strong reduction in allowable NOx emissions will be the key development drivers for the coming years.
GHG Phase 2, with key introduction dates of 2021, ‘24, and ’27, aims to achieve a total efficiency improvements of 4-5% for vocational and tractor engines, compared to a 2017 baseline. This is something Michael sees as a significant challenge.
Michael Franke, FEV North America Vice President Diesel and Commercial Powertrains Infineum International Limited
Every remaining area of loss in today's highly developed engines need further improvements, and every 10th of a percent improvement can be claimed as success. When looking at the mechanical losses, we will see improvements in friction losses through engine downsizing, bearing optimisation and piston-ring-liner optimisation, but also through electrification of auxiliaries such as a water pump and variable displacement oil pumps. Demand controlled cooling and lubrication will accelerate the engine warm-up and improve part load efficiency.
Needless to say, that further advancements in lubrication oil would also contribute to engine friction reduction.
Besides the reduction in mechanical losses, we will also see significant improvements in gas exchange systems with higher efficient turbochargers and improved EGR systems with EGR pumps, to enable high efficient turbocharger efficiency. Also, the combustion system has potential up to 1% efficiency improvement through higher compression ratios, combustion bowl designs for better air/fuel mixing and advanced controls of the injection system.
When it comes to meeting future NOx regulations Michael says there is a need for new technical solutions. “Today's diesel engines, with a typical DOC, DPF and SCR aftertreatment system, are very clean under ideal operating conditions. However, in the real world, these conditions are not always present, for example, during engine warm-up after a cold start or in extended idle or low-load operation. At these times the exhaust temperature is too low to maintain a SCR temperature of greater than 200° C, to ensure high NOx conversion efficiency. While we need new technologies to heat up and maintain the temperature of the SCR, so as to meet GHG Phase 2 requirements, these heating methods need to be more fuel-efficient than they are today.”
Michael sees OEMs introducing a wide range of effective solutions to meet the NOx challenge such as exhaust camshaft phasing, cylinder deactivation, and insulation of the exhaust system, engine electrification and mild hybridisation, but feels more will be needed.
Michael Franke, FEV North America Vice President Diesel and Commercial Powertrains Infineum International Limited
In order to reduce NOx limits by 90% beyond today's limits, down to 0.02 g per horsepower-hour, we need additional measures such as moving a second SCR much closer to the engine and a dual urea dosing system.
Impacting future fluids
These hardware and operational changes will clearly impact the design of future passenger car and commercial vehicle engine oils and transmission fluids.
Engine oils will continue to trend to lower and lower viscosities to help reduce friction losses. However, they must also deliver sufficient engine and aftertreatment protection at much higher levels of thermal loading over longer service intervals.
Click here to read our latest article on North American viscosity grade trends.
Lower viscosity is also an important feature of automatic transmission fluids as OEMs work to reduce drag losses in order to contribute towards fuel economy improvement. And, as hybrid and full electric volumes grow, specialised fluids with the correct electrical properties, materials compatibility and thermal capacity will be increasingly important. However, it is essential that these more advanced fluids also provide improved friction performance, advanced gear protection and better foam and oxidation control.
June update
A lot has happened in the four months since the material for these interviews with FEV was collected. As we get back to the new normal in the next few months, many will ask 'what has changed to alter these projections?’ - a question we recently put to Mayank Agochiya, Managing Director of FEV North America Consulting. “I think it is still too early to assess the final structural consequences of the COVID pandemic," he told us. “But, I believe short term passenger vehicle sales will fall around 20-40% in the US, EU, & India and recover in a 'U'-shape over the next year to a year and a half. The impact for China and Korea will have been limited and recover rather quickly (‘V'-shape). When I look at electric vehicles, except for China and Europe, I see a negative impact on xEVs, at least in the short term. With OEMs expected to reduce R&D budgets by ~15–20% in the short term, we expect some early stage EV programs to be delayed. However, there have been other OEMs, such as VW and GM, who have publicly committed to maintain their BEV focus.”
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