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A vehicle fleet of seven low-mileage gasoline direct injection (GDI) vehicles from the U.S. market were tested to determine if GDI injector deposits were present causing a loss in fuel economy (FE). The real-world vehicles were tested “as-is” from the field. The data shows that, even in a deposit control additive (DCA) mandated market that uses E10 gasoline, injector deposits can still result in up to 2.7 % loss in FE. In addition, the data shows that the level of real-world FE loss is comparable to that demonstrated in the GDI injector fouling test developed to simulate real-world dirty-up of GDI vehicle injectors.

A critical market driver for rear axle lubricants continues to be the improved fuel efficiency, which is related to improvements in power transfer efficiency. Power transfer efficiency improvements are achieved with a reduction in the kinematic viscosity (KV) of rear axle lubricants. General Motors (GM) recently reduced the recommended viscosity grade for their rear axle lubricants from the Society of Automotive Engineers standard (SAE) 75W-90 to SAE 75W-85. This reduction in viscosity continues to require the optimization of rear axle lubricants to ensure durability. Lubricants that form thick elastohydrodynamic (EHD) films and are shear stable even when lower kinematic viscosities are required. This work depicts how a rear axle lubricant was developed and improved with the proper selection of base oil and polymer. This newly developed SAE 75W-85 rear axle fluid was incorporated as factory fill in 2019 in T1 LDPU-GMC Sierra and Chevrolet Silverado 1500 series pickup trucks.

There is still a need in the industry for engine oils that have low viscosities to improve vehicle fuel efficiency but also protect engines from wear. Viscosity modifiers (VMs) are chief additives responsible for adjusting the viscometric characteristics of automotive lubricants. Most notably, VMs have a significant impact on a lubricant's viscosity-temperature relationship as indicated by viscosity index (VI), cold cranking simulator (CCS) viscosity, and high temperature high shear (HTHS) viscosity of engine oils. Functional copolymers bearing branched, linear, or anti-wear functionalities have been synthesized and evaluated for viscometric and wear protection performance. The resulting polymers improved tribofilm formation, shear stability and CCS viscosities. Indirect benefits including Noack improvement and trim oil reduction were observed.

After new transmission lubricants are developed there is an extensive validation program where friction durability testing is performed on multiple clutch materials. Each durability test can run for long terms and the entire validation program can take much longer terms. A well designed lubricant and friction material will deliver the necessary friction control for construction equipment to operate at optimum level. A mechanistic construct has been evaluated to calculate friction durability in clutch systems based on fluid and surface tribological properties. Fluid properties include both boundary frictional and rheological effects. Surface properties include elastic modulus, surface roughness, asperity density and asperity tip radius. Using this mechanistic construct friction durability has been predicted.

There has been a trend in the automotive industry toward the use of lower viscosity engine oils as fuel economy requirements become more demanding across the globe. Lower viscosity fluids may improve fuel economy due to their improved pumpability, lower churning losses, and thinner lubricating films. However, there is one important caveat related to the use of these fluids: the amount of improvement, if any, is hardware design and application dependent. Standard industry fuel economy tests and engines with differing designs may show divergent responses when using lower viscosity engine oils, not always showing an improved fuel economy response. This paper summarizes the work conducted by the authors to demonstrate how and why the inconsistent results in fuel economy can occur with low viscosity oils.

Friction reduction in lubricated components through engine oil formulations has been investigated in the present work. Three different DI packages in combination with one friction modifier were blended in SAE 5 W-20 and SAE 0 W-16 viscosity grades. The friction performance of these oils was compared with GF-5 SAE 5 W-20 oil. A motored cranktrain assembly has been used to evaluate these, in which friction mean effective pressure (FMEP) as a function of engine speeds at different lubricant temperatures is measured. Results show that the choice of DI package plays a significant role in friction reduction. Results obtained from the mini-traction machine (MTM2) provide detailed information on traction coefficient in boundary, mixed and elastohydrodynamic (EHD) lubrication regimes. It has been shown that the results from the cranktrain rig are fairly consistent with those found in MTM2 tests for all the lubricants tested.

Countries from every region in the world have set aggressive fuel economy targets to reduce greenhouse gas emissions. To meet these requirements, automakers are using combinations of technologies throughout the vehicle drivetrain to improve efficiency. One of the most efficient types of gasoline engine technologies is the turbocharged gasoline direct injection (TGDI) engine. The market share of TGDI engines within North America and globally has been steadily increasing since 2008. TGDI engines can operate at higher temperature and under higher loads. As a result, original equipment manufacturers (OEMs) have introduced additional engine tests to regional and OEM engine oil specifications to ensure performance of TGDI engines is maintained. One such engine test, the General Motors turbocharger coking (GMTC) test (originally referred to as the GM Turbo Charger Deposit Test), evaluates the potential of engine oil to protect turbochargers from deposit build-up.

Different mechanical components in a vehicle can be made from different steel alloys with various surface treatments or coatings. Lubricant technology is needed to prevent wear and control friction on all of these different surfaces. Phosphorus compounds are the key additives that are used to control wear and they do this by forming tribofilms on surfaces. It has been shown that different operating conditions (pressures and sliding conditions) can influence the formation of tribofilms formed by different anti-wear additives. The effect of surface metallurgy and morphology on tribofilm formation is described in this paper. Our results show that additive technology can form proper tribofilms on various surfaces and the right combination of additives can be found for current and future surfaces.

There has been a global technology convergence by engine manufacturers as they strive to meet or exceed the ever-increasing fuel economy mandates that are intended to mitigate the trend in global warming associated with CO2 emissions. While turbocharging and direct-injection gasoline technologies are not new, when combined they create the opportunity for substantial increase in power output at lower engine speeds. Higher output at lower engine speeds is inherently more efficient, and this leads engine designers in the direction of overall smaller engines. Lubricants optimized for older engines may not have the expected level of durability with more operating time being spent at higher specific output levels. Additionally, a phenomenon that is called low-speed pre-ignition has become more prevalent with these engines.

Improving vehicle fuel efficiency is a key market driver in the automotive industry. Typically lubricant chemists focus on reducing viscosity and friction to reduce parasitic energy losses in order to improve automotive fuel efficiency. However, in a transmission other factors may be more important. If an engine can operate at high torque levels the conversion of chemical energy in the fuel to mechanical energy is dramatically increased. However high torque levels in transmissions may cause NVH to occur. The proper combination of friction material and fluid can be used to address this issue. Friction in clutches is controlled by asperity friction and hydrodynamic friction. Asperity friction can be controlled with friction modifiers in the ATF. Hydrodynamic friction control is more complex because it involves the flow characteristics of friction materials and complex viscosity properties of the fluid.

Low speed pre-ignition (LSPI) is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged engines. Because of the potential to catastrophically damage an engine after only a single pre-ignition event, the ability to reduce LSPI frequency has grown in importance over the last several years. This is evident in the significant increase in industry publications. It became apparent that certain engine oil components impact the frequency of LSPI events when evaluated in engine tests, notably calcium detergent, molybdenum and phosphorus. However, a close examination of the impact of other formulation additives is lacking. A systematic evaluation of the impact of the detergent package, including single-metal and bimetal detergent systems, ashless and ash-containing additives has been undertaken using a GM 2.0L Ecotec engine installed on a conventional engine dynamometer test stand.

When gasoline-fueled vehicles are operated in consumer service, the oil used to lubricate the engine plays a key role in engine cooling, reducing friction, maintaining efficient operation, and optimizing fuel economy. The effects of normal vehicle operation on oil deterioration have a direct impact on fuel consumption. The authors have observed substantial differences between the deterioration of engine oil and resulting fuel economy under real-world driving conditions, and the deterioration of oils and resulting fuel economy in the standard laboratory test used to assess fuel economy in North America, the Sequence VID engine test (ASTM D7589). By analyzing the data from vehicles and comparing these data to the Sequence VID the authors have proposed and evaluated several changes to the Sequence VID test that improve the correlation with real-world operation and improve test discrimination.

This report focuses on an extended investigation of the durability of Dual Clutch Transmission (DCT) fluids. The performance requirements of DCT fluids differ from those of traditional step automatic transmission fluids. For that reason, key performance lab tests are discussed in this paper. Friction durability is measured with a modified version of the JASO M348 SAE#2 friction plate test. In addition, results from a vehicle chassis dynamometer test are discussed. This test involves running a 2008 Volkswagen GTI for 60,000 dynamometer miles (42,000 cycles) of severe acceleration and high speed conditions. Finally, a new DCT fluid, which performs well in these tests, offers friction stability and superior wear protection of transmission hardware, when compared to the commercial reference fluid.

This paper reports its findings in three separate parts. First, a comparative study is made among existing commercial dual clutch automatic transmission fluids (DCTFs). Significant differences in fluid torque capacity, friction material compatibility and copper corrosion performance were found among the fluids. Second, both a new vehicle chassis dynamometer durability test and a SAE#2 durability procedure are offered, specifically designed for DCTs. A 2008 VW GTI did well in the severe 60,000 mile chassis dynamometer procedure. Third, a new DCT fluid is discussed.

This laboratory presents a new step-automatic transmission fluid with enhanced friction durability and robustness for the Asian marketplace. This mineral-oil-based fluid also meets JASO M315-1A performance requirements on torque capacity, anti-oxidation, anti-wear, extreme pressure (EP), anti-aeration/foam control, copper corrosion and anti-rust performance. The fluid offers a JASO M349 low velocity friction apparatus (LVFA) durability lifetime of over 1100 hours. Moreover, this fluid maintains stable torque capacity during its entire LVFA durability lifetime, across the temperature range of 40 to 120 °C. Similarly, friction level changes with sliding speed are smaller than experienced by other commercial factory-fill ATFs. These critical performance features are due to a new fluid friction system approach, which may enable new types of transmission hardware or calibration.

A model and simulation results are presented for the torsional dynamics of a rear wheel driveline while the vehicle is coasting in a turn. The model includes the effects of road load and powertrain drag, limited slip differential clutch friction, the inertias of the vehicle, wheels, axles, differential carrier, and driveshaft, the final drive ratio, torsional stiffnesses of the axles and driveshaft, vehicle track width, and radius of the turn. The dynamics of coasting in a turn differ from powered driving due to changes in the inertia loading the driveshaft, the damping effect of the disengaged transmission, and nonlinearities in the clutch friction. Specific focus is given to vibration in the axles and driveshaft due to variations in the torque-speed slope of the clutches, which is determined by the slope of the friction coefficient ‘μ’ versus sliding speed ‘v’ in the limited slip clutches.

This paper provides an overview of driveline fluids, in particular automatic transmission fluids (ATFs), and is intended to be a general reference for those working with such fluids. Included are an introduction to driveline fluids, highlighting what sets them apart from other lubricants, a history of ATF development, a description of key physical ATF properties and a comparison of ATF fluid specifications. Also included are descriptions of the chemical composition of such fluids and the commonly used basestocks. A section is included on how to evaluate used driveline oils, describing common test methods and some comments on interpreting the test results. Finally the future direction of driveline fluid development is discussed. A glossary of terms is included at the end.

Multiple plate disc clutches are used extensively for shifting gears in automatic transmissions. In the active clutches that engage or disengage during a shift the automatic transmission fluid (ATF) and friction material experience large changes in pressure, P, sliding speed, v, and temperature, T. The coefficient of friction, μ, of the ATF and friction material is a function of these variables so μ = μ(P,v,T) also changes during clutch engagement. These changes in friction coefficient can lead to noise or vibration if the ATF properties and clutch friction material are improperly matched. A theoretical understanding of what causes noise, vibration and harshness (NVH) in shifting clutches is valuable for the development of an ATF suitable for a particular friction material. Here we present a theoretical model that identifies the slope, ∂μ/∂T, of the coefficient of friction with respect to temperature as a major contributor to the damping in a clutch during engagement.

Modern light-duty trucks and SUV's are designed to be aerodynamic to increase fuel economy. Such vehicle design significantly reduces the amount of air available to cool the rear axle in rear wheel drive vehicles. Reduced cooling coupled with higher power output and additional load from trailer towing operations results in higher axle operating temperatures, especially during the early operation or “break-in” phase of axle life. Higher axle operating temperatures decrease oil viscosity resulting in reduced oil film formation ability to protect against wear and contact fatigue. High temperature also shortens the useful life of gear oils. To facilitate the development of gear oils capable of reducing axle operation temperature, we have developed a laboratory simulation test method that can closely simulate actual trailer-towing driving on Baker's grade road under maximum GVCWR of close to 6,033 kg (13,300 lbs).

The torsional natural frequencies of axles equipped with limited slip differential clutches depend on whether or not the tires and clutches are slipping since the effective inertia at each end of the axle is different for slipping and non-slipping conditions. Limited slip axle vibrations are typically analyzed for one tire slipping and the other not since that is the case for which the limited slip clutches are used. Vibrations often arise, however, during normal turning when both drive tires have good traction.