Real-Time Oil Consumption Measurement on the Road

Oil emissions from the engine waste money and interfere with exhaust gas aftertreatment. IAV has now developed a mobile version of its proven, long-standing measurement technology to cope with this problem. In cooperation with US engine manufacturer Cummins, investigations have been carried out on the road and in real time to demonstrate how oil emissions depend on engine torque and engine speed as well as different driving conditions and operating points. This measurement method provides new ways of optimizing engines for minimum oil consumption.

Most of the engine oil consumption (approx. 90 percent) comes from unburned oil, which enters the exhaust system for example as blow-by via the piston rings. The consequences are unnecessary oil refill and poorer conversion rates in the exhaust gas aftertreatment system, for example as a result of ash accumulation. Modifications to the base engine – such as the piston rings, turbocharger or oil separation system – provide potential for reducing oil consumption. However, changes of this type first require exact information on operating states that emit particularly large quantities of oil.

For this, IAV has been using a measurement method for over ten years that determines emissions using a mass spectrometer. The unique selling proposition is the calibration method developed in-house that can be used at any time on the test bench or in the vehicle. “Normally the devices are calibrated once in the laboratory prior to measurement”, explains Tom George, Director Business Development Commercial Vehicle at IAV. “If necessary, this is something we can always repeat which makes the results more accurate.”

So far, the measurement method has been restricted to use on the engine test bench and vehicle roller benches which means it has not been possible to gain any findings from real-world driving (for example on the influence of cornering or climate and altitude). On top of this, future transient homologation cycles will demand methods that are both precise as well as real-time-capable. This led to the idea of developing a mobile version of the system and setting up the “IAV Mobile Oil Emission Measurement System”. As a partner, IAV was able to team up with Indiana-based engine manufacturer Cummins which is well known for its diesel engines for trucks, pickups and other commercial vehicles. “Cummins already had an emission measurement trailer”, George says. “We integrated our mass spectrometer into it, enabling us to carry out a large number of test drives on highways and subsidiary roads.”

First, it meant overcoming a number of challenges. For instance, vibrations in the trailer interfered with the sensitive mass spectrometer. This was remedied by silicone dampers which were able to suppress the main vibrations. In addition, the exhaust gas had to be fed from the tractor into the trailer via a line measuring over ten meters in length. Given the low flow velocity, a vacuum pump was used to keep the flow of gas constant. To match up measurement readings and driving states correctly, a computation methodology was developed that takes account of the time lag in feeding the exhaust gas through the sampling line.

Following this groundwork, measurements were able to get underway. The test vehicle used was a Peterbilt 579-type truck with a 506 HP diesel engine. Lasting some three weeks, the measurement drives in Indiana showed the experts from IAV and Cummins clear differences between behavior on the test bench and road. Not only was it possible to identify an impact of cornering, engine braking was also shown to be particularly critical. “This involves very high pressures and temperatures”, says George. “In particular, oil consumption increases rapidly after the end of the braking phase. This is hard to reproduce on the test bench.” The measurement results were presented at the SAE World Congress in Detroit and at the International Engine Congress in Baden-Baden, Germany. The mobile oil consumption measuring system could also be used in the passenger car. Therefore IAV already had initial talks with clients to start passenger car testing in 2018.

Dr. Thomas L. McKinley talking about the project and working with IAV

The first real-time, on-road oil consumption measurements were made possible by combining the know-how of Cummins and IAV teams. Cummins brought extensive testing experience, along with an emission trailer containing sophisticated emission measurement equipment and high-speed data acquisition systems. The IAV team complemented this with extensive mass spectrometry experience.

“We had confidence in IAV from previous real-time oil consumption measurements in our test cells, but realized that testing on engine dynamometers is much more expensive, limited, and time-consuming than it would be on-road” says Dr. Tom McKinley, System Integration & Validation Director at Cummins. “We only had a short, three-week test period before the emission trailer would be required for other urgent experiments. Excellent planning and preparation of the measurement series by both companies made the difference and allowed us to master the challenges of this new measurement method”, McKinley adds. “We were very impressed with how well IAV anticipated issues and came to us with solutions before the testing began. Some of their innovations will improve test cell testing, too. It was great to see the two companies working together as one team, focused on success.”
The dual benefits of lower testing cost and a modular testing platform which can be easily moved from truck to truck made the exploratory effort worthwhile. McKinley comments: “While we were primarily interested in demonstrating measurement capability, we also came away with new insights into oil consumption behavior. For example, we developed a ‘transient map’ to predict average oil consumption across different applications and a detection method for finding spikes or overshoots in oil consumption.”

Moreover, this is just the beginning for this novel measurement approach. McKinley adds: “We’d like to use the method to expand our knowledge of oil consumption over a wider range of operating conditions and commercial vehicles, including competitive benchmarking. It is extremely difficult to get accurate average oil consumption data from the field, let alone understanding the transients that affect it. Mobile, transient measurements open up a wide range of opportunities for us.”