Ekonomisk och energieffektiv användning av motorvärmare: utvärdering av effekten på bränsleförbrukning vid värmning av smörjolja jämfört med värmning av kylvatten

Ulf Hammarström

Test results show that the cold-start effect with increased fuel consumption is reduced most by heating the cooling water, compared to heating the lubricating oil. Starting an engine when it is cold gives rise to higher fuel consumption and emissions as a cold engine means that a larger friction needs to be overcome and that the combustion is not optimal. To warm the engine in beforehand leads to lesser cold start effect. Traditionally, engine heating has been made by heating the cooling water, which in turn heats the engine block. The purpose of this study was to examine whether it would be more energy efficient to heat the lubricating oil instead of the cooling water. The hypothesis was that a warmer lubricating oil leads to less friction in the engine, which in itself would mean that less fuel to overcome the frictional resistance is needed. Likely, there may be differences in the usefulness of engine heater between cars with gearbox integrated with motor and without such integration. The results of the tests show that the cold-start effect with increased fuel consumption is reduced most by heating the cooling water. The warmer the cooling water is at engine start, the less fuel consumption by the engine start. When the total energy needs for cold starts is calculated, i.e. fuel consumption plus electric use due to engine heating, the results are not as clear regarding which option is the most energy efficient. The reduced fuel consumption as result of pre-heating is overcome by the electricity consumption needed for the actual motor heating. One advantage is that the local emissions will decrease. Since the Swedish electricity production to a large extent is based on emission free production technology, it is most likely that the total emissions are reduced.



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