Balanced e-fluids for commercial vehicles
23 January 2024
05 September 2023
SwRI engineers on the key work around tests for upcoming API specifications, and the developments that will shape the future transportation industry
The largest challenges facing today's transportation industry are meeting sustainability and decarbonisation targets while also complying with increasingly stringent emissions mandates. OEMs and suppliers are looking at every part of the powertrain for contributions and are innovating rapidly to meet the requirements. Andy Ritchie, Infineum Industry Liaison Advisor, met up with a group of engineering leaders from Southwest Research Institute (SwRI) to discuss current lubrication specification initiatives, the future mix of different electrified powertrains, and the role new low carbon fuels could play in the journey to a zero carbon transportation landscape.
Headquartered in Texas, US, SwRI is a leading independent, non-profit research and development organisation employing over 3,000 people. Its Office of Automotive Engineering designs, develops and tests a wide range of components, engines, transmissions and vehicles to help address difficult technical issues such as emissions reduction and efficiency improvement.
As two organisations recognised internationally for their fuels and lubricants research, Infineum and SwRI have worked together on many innovative research projects. The services SwRI provides to Infineum are generally split between their Powertrain Engineering Division and their Fuels and Lubricants Research Division. The former provides consultancy support on the latest and future government regulations, basic research studies, and product development support to hardware manufacturers. The latter translates the needs of OEMs to develop standardised lubricant evaluation test methods, which provide the framework for API, OEM and other lubricant specifications.
In this interview we wanted to tap their knowledge on the key trends shaping our industry and find out how the results of fundamental research projects help not only develop new lubricants to support these changes but also create standardised test methods to formally evaluate lubricant performance.
First some background from Terry Alger, Executive SwRI Director of Sustainable Energy and Mobility and Pat Lang, Manager of Gasoline and Specialized Lubricants Evaluations. Here they describe how the Powertrain Engineering Division and Fuels and Lubricants Research Divisions combine their efforts to first study new problems, then develop standardised test methods to evaluate the impact of the lubricant to respond to these new challenges.
Terry Alger & Pat Lang, SwRI
We have two major business units in the Office of Automotive Engineering. The first business unit is engaged primarily in research and development, so we're interested in looking at problems in the 5 to 15 year timescale or maybe even longer in some circumstances. That group is engaged in innovation, doing the fundamental research to help companies develop new products to solve future problems. The other part of our business unit is primarily engaged in standardised testing and helping our customers qualify the products that they make today for sale in the marketplace now. We typically work together quite closely. The knowledge of what we do now to qualify our products informs us in what we're developing for the future.
Test development generally starts in response to a recognised field problem, but more recently we are engaging with these new challenges earlier in the development cycles. A project may start with a fundamental research study, but it often ends with the adoption of a standardised dyno test method. It requires a very significant effort from teams of industry participants to do this properly and we play a central role in helping to facilitate this. The Sequence IX LSPI test is the best recent example of taking the findings from numerous research projects and translating them into a standardised test method, and there are many more challenges presenting themselves right now.
Evaluating ICEs with e-fuels. for example, hydrogen and ammonia might mainly be research projects right now covered by my colleagues in division three, but they could very well end up as ASTM dyno tests to evaluate lubricant performance developed by my colleagues in division eight. We want to be the first lab to run ammonia and hydrogen IC engine lubricant evaluation dyno tests.
Pat Lang and Robert Warden, Manager of Diesel Lubricant Evaluations, gave their views of the key activities around new ILSAC GF-7 passenger car motor oil (PCMO) and API PC-12 Heavy-duty diesel (HDD) specifications. The primary goal of both these new specifications is to help auto and truck manufacturers meet the new requirements for fuel economy and emissions slated to be introduced in 2027. In order to comply with mandatory waiting periods, set forth by API, the process has already started and needs to progress rapidly. Both specifications rely mostly on older tests but, as Pat explains, there is significant work to be done on ILSAC GF-7 to hit the proposed 2024 timing.
Pat Lang, SwRI
We do expect that there will be a number of new test development efforts for the new ILSAC specifications, which includes some bench tests and we are ready to partner with the industry to develop these new test methods. A new Sequence VI, a new Sequence V, and a new NOACK volatility test method are just three items which have been raised.
One of the recent light duty test developments is the aged oil LSPI test, which is almost complete and has been a success.
With such a tight turnaround for ILSAC GF-7 we were keen to find out if Pat thinks there are any issues on test parts availability.
Pat Lang, SwRI
We think it is possible that we have enough test parts available to meet the demands of an early ILSAC GF-7 introduction, but it certainly needs a close look at the inventories of test parts and projections for their usage based on different scenarios around different test limits and the possible introduction of alternative tests. As we've found in the last two years with the Sequence VH test, higher performance limits are generally associated with higher levels of testing. One proposed option is to replace the Sequence VIF for 0W-16 ILSAC GF-6B with the new Toyota M 366 test. This would certainly help a lot by allowing all of the remaining Sequence VI hardware to be assigned solely to the Sequence VIE test for ILSAC GF-7.
Over on the HDD side, Robert Warden goes on to explain that, along with the development of replacements for the Mack T8, 11 and 12 and roller follower wear tests and the introduction of the Daimler DD13 scuffing and Ford valvetrain wear tests, there are also expected to be tighter chemical limits.
Robert Warden, SwRI
So chemical limits for PC-12 are anticipated to be lower than they were for the CK-4 and FA-4 categories, but not quite as restrictive as the ACEA E8 specification for sulphur and phosphorus. The ash content of the oil is one area that OEMs seem to be aligning on falling down at the 0.9% range below what ACEA and the API specifications currently allow. One additional area that OEMs have a lot of interest in is the possible addition of a phosphorus retention parameter to ensure that oil starting at a lower level of phosphorus maintain those compounds in the oil throughout the useful life of the oil in the engine. For many of the OEMs, this reduction in phosphorus is in an effort to ensure the longer duration life of their aftertreatment systems. However, it comes with the trade off, placing a lower chemical box around what can be in the oil restricts formulating spaces that the lubricant companies are allowed to operate in and takes out some components that were put in the engine for very good reasons, such as wear protection and detergency. There's gonna be long-term trade off between the durability of the internal components and the survivability of the aftertreatment that OEMs are gonna have to balance.
With lubricants trending to lower viscosities for fuel economy advantages the need to ensure continued hardware protection in a tighter chemical box will be increasingly challenging. In addition, Robert suggests this trend to lower viscosity means changing the reference oils used in PC-12 is also important.
Robert Warden, SwRI
So reference oils that would be needed for PC 12 include ones that are gonna be operating in that lower viscosity regime that we're trying to introduce with PC 12B. Either say an XW 20 or even a lower viscosity xW-30, similar to what the FA-4 category was. We need to be moving in that direction and away from the prevalency of 15W-40 reference oils that many of the existing tests utilise.
To help support this move into the lower viscosity range. The industry really needs to be investing in running these new reference oils and establishing precision based on them, not just assuming that the precision levels of the higher viscosity grades are gonna transition over.
Clearly emissions regulations are driving significant hardware change. But, by far the biggest challenge facing the transportation industry is the drive for more sustainable mobility as part of the commitments the world has made to becoming carbon neutral by 2050. No part of the powertrain is exempt from reducing its carbon intensity and, to meet the required pace of decarbonisation, OEMs and suppliers alike are innovating rapidly. We asked Terry Alger his thoughts on what sustainable mobility means.
Terry Alger, SwRI
A sustainable marketplace is one that is environmentally conscious, doing the right thing with respect to emissions and CO2, but it's also one that generates a sustainable business for the people practising it. So you have to have products that are affordable and desired by the consumer and the people that make those products have to be able to make a sustainable profit.
Many OEMs see full powertrain electrification as the best strategy to meet decarbonisation and sustainability goals. However, as Thomas Briggs, Staff Engineer in SwRI’s Powertrain Engineering Division explains, it’s far from a one-size-fits-all market.
Thomas Briggs, SwRI
So it's been fun to watch over the past year or so as we see on one hand news reports saying the IC engine is dead and that everything's going to be electrified. And then we see again and again, a lot of the mainline manufacturers announcing they're doing a whole new engine design or the next generation of an existing engine design.
There's a huge market, billions of people that need mobility, that an IC engine probably remains the most affordable and practical solution for them for many, many years. So where we sell those engines may move, but there's still going to be a large and growing market for those IC engines going forward. The question is how do we make it sustainable? How do we decarbonise in a way that's effective, efficient, and economically viable for these markets.
Graham Conway, Low Carbon Technologies Group Manager at SWRI, builds on these thoughts with views on a multi-pronged approach to meet decarbonisation and sustainability goals.
Graham Conway, SwRI
So the automotive market and the transportation sector comprises of many different technologies and many different sizes of vehicles. I think we have to see a split and a multi-pronged approach to decarbonising each sector. For the smaller vehicles, it's clear that heavy electrification will be the way forward, for the very largest sectors, such as marine, rail and aviation, I think this is where we will see a big push for renewable fuels, so the low carbon fuels which can drop into these applications. Unfortunately for low carbon fuels, the resources required to make them are finite, and so that's why I think we should limit them for the largest vehicle applications. In the middle, where we have the class eight applications and maybe some of the off-road applications, this is a role where hydrogen can fill and we may see hydrogen used in these sectors either as a fuel cell or an internal combustion engine.
For sustainability, I personally believe we need to look at all of the options that are available to us. We can't put all our eggs in one basket. We need to look at hybridisation, low carbon fuels, as well as fully electric solutions for the transportation sector because we won't get there in the shortest possible time if we just focus on one technology.
Full electrification clearly make sense in light-duty applications in regions where electricity is largely generated from renewable sources. But, in larger applications and in regions relying on fossil fuels for power generation, the internal combustion engine (ICE) – either as part of a hybrid configuration or running on green fuels – can be a better fit. SwRI certainly feels hybrids will have a big part to play in the future.
Terry Alger, Thomas Briggs & Graham Conway, SwRI
I personally think that hybrid electric vehicles in the short term are a very, very good solution. And the reason I say that is because our current battery production is quite limited, and until we can bring more battery production online, I think we can get a bigger CO2 savings by going to more hybrid electric vehicles. And each one of those would contribute to a reduction in CO2 versus a limited number of battery electric vehicles. I think we can make a bigger difference on the environment by doing more now, even if it means we delay perfection by a year or two in the future.
So we probably see a much brighter future for hybrids than you would think based on the regulations today, simply because at some point we come against people's practical need for mobility. And a hybrid is a really, really good technical solution for that practical need.
I think using hybrid powertrain is the best way to use the rare earth materials we have. For example, a fully electric sedan might have a 60 kilowatt hour battery pack, with a fully renewable grid, that vehicle can result in a 50 tonne CO2 benefit versus an internal combustion engine counterpart. Now a hybrid vehicle with a 1.6 kilowatt hour battery pack means you can create 35 of those vehicles for the same size of battery pack. The hybrid gives a 15 tonne benefit, and so overall you can get a 550 tonne benefit by the hybrid use of those materials versus an electric vehicle. So that's 10 times the carbon footprint reduction compared to an electric vehicle, when using the hybrid.
However, there are challenges to overcome in hybrid lubrication, mainly owing to the duty cycle, where the engine undergoes a high number of high power cold starts.
Graham Conway & Pat Lang, SwRI
For some of these new hybrid vehicles, especially plug-in hybrid vehicles, the engine operating characteristics and the vehicle speed aren't linked as they are in a traditional internal combustion engine vehicle. One extreme example of this is cold start. For a plug-in hybrid electric vehicle, the engine might not turn on until an aggressive acceleration event, for example, moving onto a freeway. This creates problems with cold start durability and places an increased onus on the lubricant to provide durable and consistent operation.
One new test challenge is the evaluation of lubricants with hybrid duty cycles, stop/start and repeated cold cycles. A new dyno test is needed, which challenges the lubricant to handle emulsions, water separation and minimise corrosion and rust. We have an engine installed right now, which is doing just that.
In addition, as Peter Lee, Chief Tribologist at SwRI explains, the fact that the engine remains off for substantial periods in hybrids can cause lubrication challenges.
Peter Lee, SwRI
So if you have an engine that doesn't turn on very often and it just runs for short period of time, you end up with a lot of water in the oil and then you end up with an emulsion.
No lubricant with water in is good for an engine. So even a hot cold, cold hot cycle where you, you start the vehicle and you've got an emulsion and then you use it so it gets hot and you burn that emulsion off or burn the water off, it's still not good for an engine because it still had the water in there at some point doing the damage that it does.
First of all, it's corrosive, so you end up with parts corroded in an engine, but also it can block some of the pipes and other things that are required for gas movement around the engine and other areas like that. So yeah, it, it can cause some significant issues.
The ICE looks set to be a big part of the future of mobility in some applications and markets. Making this established technology sustainable is the key challenge, and here the development of engines running on fuels such as green hydrogen, ammonia and methanol will be key to its future success. Although as Ryan Williams, SwRI Spark Ignited Research and Development Manager, and Terry Alger suggest, again there is not a one size fits all solution.
Ryan Williams & Terry Alger, SwRI
I think the future of the internal combustion engine will really depend on multiple solutions. I don't think there's any one perfect solution that's going to work for every application. There will be some applications where e-fuels and liquid fuels will be essential, especially in the very power dense applications where you either need range or a lot of energy for an extended period of time. And then there are other applications like hydrogen, that will work, and, of course, you know, the ammonia fuels and other energy carriers with zero carbon, that I think will also serve a purpose. But, each one has its own specific application where it makes the most sense.
Each fuel has its own set of advantages and disadvantages. Hydrogen is a wonderful fuel. It's got a very high octane number, it's very dilution tolerant, so you can run it extremely lean or very high levels of exhaust gas recirculation. The big benefit that hydrogen has over ammonia is that if you have a release of hydrogen, it isn't toxic to people.
I think the low carbon fuels bring a lot of challenges to the lubricant and so the lubricant will have to be modified and may become a significant part of making that engine successful.
Whilst SwRI is exploring a range of future fuel options, it has undertaken a major research project kicking off a hydrogen internal combustion engine (H2ICE) consortium to explore its potential in a heavy-duty Class 8 vehicle. Here the engineering and lubrication challenges are being assessed, with the aim of demonstrating a clear pathway for getting H2ICE to market.
Thomas Briggs, Terry Alger, Ryan Williams, Peter Lee & Graham Conway, SwRI
We have an active and growing hydrogen engine development and research programme, including some large joint industry programmes where we're trying to get initial product out ahead of even the prototype hardware that industry's supplying so that we can see what the true environmental impact is. That's also gonna give us the chance to start looking at some of these lubricant challenges and in fact, part of that programme is going to be working between our powertrain engineering division and our fuels lubricants division to set up a test stand where we can start to do the pre-development work towards the idea of an ASTM standardised test as we move into the years to come.
The biggest engineering challenge for a hydrogen engine right now is the boosting system. The reason the boosting system is the largest challenge is we need to have the air fuel ratio high enough so that we do not have frequent pre ignition in the engine. Given the low exhaust temperatures of a very lean engine, which the hydrogen engine is, in order to prevent that pre ignition, it's very, very difficult to make the boost levels that we need to maintain that air fuel ratio. So you kind of have a chicken the egg problem where we need to be very lean because we don't want to pre ignite, but that leads to cool exhaust temperatures, which makes it hard to boost the engine, which makes it hard to be lean.
One of the big challenges for hydrogen right now as a fuel, is the injector hardware that we have available. To be able to get to a point where we're on par with the same power density as current diesel engines, we'll need to move to a direct injection solution, but that hardware is still maybe three to five years away.
Tribology has a large role to play with hydrogen. ICE There's the lubricant that needs to be looked at and we need to decide whether that lubricant might be affected by the hydrogen that it's interacting with. And also there's the embrittlement potential of the actual liner or even the piston and the rings that are in there as well.
Hydrogen also has significant problems with pre ignition, although the mechanisms behind them are unknown at this time. We know hydrogen will pre reignite very readily if it reaches a hotspot in the engine. Whether this is a metal components such as the exhaust valve or a spark plug. The interaction between the lubricant and the hydrogen is a focus of current research and development.
Right now there is some uncertainty as to what the actual impact of the hydrogen is and what we should be worried about. For example, you know, we know that burning hydrogen makes a lot of water, so we expect there to be a lot of water in the blow by, and that's something we could test for in a standardised test. But one of the questions that comes up is, is the water the primary concern or is it the fact that that water will also contain large amounts of NOx, which is gonna turn into nitric acid when it mixes with that water? And so do you want to design a test that tests mostly for emulsions and water content, or do you want to look at something that develops more of an acidic style test and you have to worry about the total acid number of the oil after an extended period of time? And so I think we're gonna need to do a considerable amount of work to understand which is the actual failure mode of the lubricant, and under what conditions.
With the ICE looking to have a place in future mobility for many years to come, investment in the development of advanced technologies is essential to make the future of transportation as green as it can be in all the markets and applications around the world. However, CO2 emissions are currently only regulated during the in-use portion of a vehicle’s life time, whereas using a well-to-wheels approach would allow a complete evaluation of the decarbonisation effect of different solutions.
Graham Conway & Thomas Briggs, SwRI
Currently in the US we regulate CO2 emissions at the tailpipe. Adopting a lifecycle analysis approach allows us to look at the entire picture of where CO2 is produced during the life of a vehicle. At the moment, the credit structure for manufacturers in the US is also based on the tailpipe. So a vehicle [OEM] which produces many large trucks might have a five mega gramme deficit of CO2 on each vehicle they sell. A manufacturer that only sells electric vehicles might get a 120 mega gramme credit for every vehicle they sell. This is a huge difference between these two manufacturers and why we see credits transferred from one OEM to another. If we adopted a lifecycle analysis approach, the situation changes completely. The internal combustion engine version might now have a 25 mega gramme deficit, but the electric vehicle could have as much as a five mega gramme deficit up to an 80 mega gramme credit. So it completely changes the situation on where credits move and how OEMs might select their powertrains in the future.
The only way to really get serious about decarbonising mobility is to bring in lifecycle assessment where we have the ability to look at that whole picture of what is the cost in terms of carbon to move me to move goods, to move whatever it is we're trying to transport so that we can then make good engineering and policy decisions about how are we going to get to a decarbonised future that benefits what we want to do environmentally.
Adopting a full life cycle analysis approach for regulating these emissions would level the playing field – enabling OEMs to select the best technology option to meet the needs of each specific market and application.