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Continued from page 6


Lower fuel consumption; see fig 6, has resulted from these changes with the oil and the electric oil thermostat and better pressure control with the Electrical PCJ-valve.


valve, to a Fixed Oil Pump with a relief valve (rFOP). Similarly oil flow has been impacted by an increasing number of consumers.


The historical evolution of the engine platform can be seen above and a further step will now be taken in terms of oil viscosity, oil temperature will remain at the current level, and oil pressure & flow in the engine will be reduced. This will lower the fuel consumption according to fig 6.


State of the art: The current situation in the HD-market in both the EU & US requires an oil viscosity of 0W-20 engine oil with an HTHS of 2.9, oil temperature of 117°C, oil pressure regulated by way of a VOP (Variable Oil Pump) and oil flow that is affected by an increasing number of consumers.


Figure 4. Current Engine Oil System diagram


A brief explanation of the Engine Oil System diagram: A fixed displacement gear oil pump supplies oil to the oil filter housing. A safety valve provides protection from high oil pressures during cold starts. Oil pressures are regulated by means of an internal pump regulation valve. Oil temperature is regulated via an electronic valve, resulting in a proportional amount of oil flowing through an oil cooling circuit. All oil flows through two full flow filters, with a safety bypass valve to allow continued oil supply in the event of a filter blockage. A bypass filter provides finer filtration to a portion of the oil. Piston cooling supply oil pressure is regulated via an electronic valve in response to load changes. The oil is supplied to the cranktrain, overhead, and ancillary components via block galleries and external pipes. For engine brake equipped engines, a control valve regulates overhead oil pressure to a preset value until an electronic valve is actuated and full system oil pressure is supplied, thus activating the engine brake.


Figure 6. Fuel Consumption improvements


Where are we heading? Next challenges – long term: How can new engines be developed to be able to run using oils with even lower viscosity, lower oil pressure, and lower oil flow and how much can, or should, the oil temperature be increased?


Can we reduce oil viscosity while raising the oil temperature, reducing oil pressure and reducing the oil flow? How should lubricants, materials, coatings, surface roughness and textures be designed to optimise the system? What are the requirements for low fuel consumption, long durability and long service intervals which all have to be met at the same time?


Oil Consumers must also be able to run with lower oil pressure and use less oil. More Oil Consumers in the future will need to be electrified.


It’s vital to continue on the path to achieve better fuel economy but at the same time keeping the durability and service interval at the expected levels. A lot of activities are currently on-going at Volvo within the next five to ten years to develop and introduce optimised engine oils for the future.


Figure 5. Why Electrical Oil Thermostat?


Fig 5 shows the benefit of using an electrical oil thermostat. It enables the engine to run with a higher oil temperature without risking high temperature swings during severe operation.


Where are we heading?


Coming back to the main issues, over the future and in the short-term, oil viscosity has moved from a 15W-40 with HTHS of 4.2, to a 10W-30 with an HTHS of 3.5. Oil temperature has increased from 90°C to firstly 105°C and then 117°C with an expectation that further increases will occur. Oil pressure has been impacted in moving from a Fixed Oil Pump (FOP) without a relief


Current lubricants in use are a Group II Base Oil. Over the short-term future development is targeting a Group III Base Oil and medium term development is targeting a Group III, IV, V or a mix thereof depending on future requirements and needs. We have also started to look into the field of renewable Base Oils which fits very well with the core values of the Volvo Group.


In the future the design of the oil needs to be balanced with engine hardware, a proper oil temperature, oil pressure, oil flow and filtration level. One key to success will be a parallel lubricant /engine hardware development.


Magnus Horn M.Sc Nav.Arch.


Global System Responsible HD - Level 2 for Engine Lubrication System Engineering Leader HD for Oil System.


HD Fluid Management Powertrain Engineering. Volvo Group Trucks Technology.


8


LUBE MAGAZINE NO.141 OCTOBER 2017


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