Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.99 page 1
Fuel economy drives change for passenger car oil formulations
Anne Young, Infineum USA, L.P. and Jonathan Flemming, Infineum UK Ltd.
Legislation and consumer demand are driving vehicle manufacturers to find ways to improve fuel economy and reduce CO2
emissions across their vehicle fleet. In the passenger car market OEMs have responded by looking for energy savings from a variety of technologies including advanced transmissions, turbocharging, engine control systems and advanced materials. Many of the easy options for efficiency gains have already been implemented and OEMs now have to look much harder at each vehicle component, which of course includes the engine oil. The passenger car lubricant development scientists at Infineum have been working on a variety of projects to support this quest for fuel economy, two of which are outlined here. The first area of focus is a phenomenon called low speed pre-ignition (LSPI) that has arisen from the downsizing of gasoline engines. The second is our research into the ways low viscosity formulations can be tailored to ensure fuel efficient lubricants continue deliver sufficient hardware protection.
Understanding low-speed pre-ignition Engine downsizing is one simple yet effective method OEMs are using to improve fuel economy. The reduced engine displacement results in less pumping and frictional losses and lower gases-to-wall heat transfer, which means the engine is more efficient. Although engine downsizing can clearly improve fuel economy, it unfortunately comes with a sacrifice of performance. This means the engine boost pressure must be increased by adding turbochargers or superchargers to compensate for lost power output.
Some auto manufacturers are already offering downsized and boosted gasoline engines in their vehicle portfolio. However they have been known to exhibit disruptive abnormal combustion, such as knocking and LSPI.
LSPI occurs early in the combustion cycle and always prior to spark-triggered ignition. Its initial combustion is relatively slow and similar to normal spark initiated combustion, but then there is significantly advanced combustion timing. This can lead to very heavy knock, which can in turn cause catastrophic damage in only a few engine cycles. LSPI is especially important for pistons and connecting rods because they are rising when the aberrant combustion event occurs. In the most severe cases, LSPI can lead to broken piston rings, damaged pistons and bent connecting rods.
An example of piston damage due to LSPI observed during testing at Southwest Research Institute®
. Photo courtesy of Southwest Research Institute® . LUBE MAGAZINE NO.128 AUGUST 2015 25
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