This content is not included in your SAE MOBILUS subscription, or you are not logged in.
An Investigation of Lubricating System Warm-up for the Improvement of Cold Start Efficiency and Emissions of S.I. Automotive Engines
ISSN: 0148-7191, e-ISSN: 2688-3627
Published October 01, 1990 by SAE International in United States
Annotation ability available
Transient warm-ups of an engine lubrication system are examined using test bench measurements and numerical simulations. It is shown that friction in the bearings is the greatest heat source for oil, but that a major part of the heat received by the oil is transferred to the walls of bearings and passages. It is also determined that the total amount of heat ultimately retained by the oil is a very small part of the engine energy consumption, and that the engine warm-up does not use all the energy made available by combustion heat transfer and friction losses. Within this scope, some systems are examined to properly use available heat and improve lubricant and engine warm-up.
Today, automotive engines are well designed for low consumption and pollutant emissions during fully warmed-up periods. However, emission standards are fixed by test-cycles which begin with cold starts. Furthermore, under city driving conditions, engines operate well below their fully warmed-up optimum fuel consumption and emission levels    . Unfortunately, cold start and warm-up of SI engines are very critical periods for fuel consumption and pollutant emissions  . It is during these periods that engines emit the largest amount of pollutants (namely carbon monoxide and unbumed hydrocarbons). This increase in pollutant emissions results from both erratic combustion induced by inadequate mixing of the air and fuel, and too rich air-fuel ratios . In addition, under cold conditions, catalytic conversion of the pollutants is inefficient due to the low temperature of the catalytic converter. Finally, since the viscosity of lubricants at low temperatures is very high, frictional effects tend to degrade the system efficiency causing increased fuel consumption.
One way to minimize these problems is to make the warm-up period as short as possible. If we analyze the temperatures of engine parts during the warm-up, it appears that lubricant is generally the last component to reach its equilibrium temperature . Thus, it is relevant to examine the lubricant warm-up process in order to characterize the thermal inertia of the engine system.
Bearing this in mind, the thermal behavior of the lubricant and lubricating system during the warm-up period of an automotive engine has been analyzed. The results are based on both experimental measurements and computer simulation.
CitationTrapy, J. and Damiral, P., "An Investigation of Lubricating System Warm-up for the Improvement of Cold Start Efficiency and Emissions of S.I. Automotive Engines," SAE Technical Paper 902089, 1990, https://doi.org/10.4271/902089.
- Austin T.C. Hellman K.H. “Passenger car fuel economy as influenced by trip length” SAE paper 750004 1975
- Eccleston B.H. Hum R.W. “Ambient temperature and trip length - Influence on automotive fuel economy and emissions” SAE paper 780613 1978
- Horowitz A.J. Tobin R.L. “The influence of urban trip characteristics on vehicle warm-up -Implication for urban automotive fuel consumption” SAE paper 790656 1979
- Andre M. “Experimental study on the actual uses of cars” SAE paper 890874 1989
- Pozniak D.J. “The exhaust emission and fuel consumption characteristics of an engine during warm-up - A vehicle study” SAE paper 800396 1980
- Andrews G.E. Harris J.R. Ounzain A. “Transient heating and emissions of an SI engine during the warm-up period” SAE paper 880264 1988
- Sorrell A.J. Stone C.R. “Spark ignition engine performance during warm-up” SAE paper 890567 1989
- Andrews G.E. Harris J.R. Ounzain A. “SI engine warm-up: water and lubricating oil temperature influences” SAE paper 892103 1989
- Huebner K.H. “A simplified approach to flow network analysis: application to engine lubrication systems” SAE paper 750080 1975
- Neu E.A. Wade J.A. Chu A.C. “Simulating the lubrication system of a diesel engine” SAE paper 770032 1977
- Booker J.F. “Dynamically-loaded journal bearings: mobility method of solution” ASME Paper n o 64-Lub-14 Journal of Basic Engineering Trans. ASME 87 o 3 537 Sept 1965
- Cameron A. “Basic lubrication theory” 2nd Ellis Horwood Limited 1976
- Martin F.A. “Developments in engine bearing design” Tribology International 16 o 3 147 June 1983
- McAdams W.H. “Heat transmission” 2nd McGraw-Hill Book Company N.Y 1942