Engine Lube - Sump Temperatures - Article Review

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1,397
Location
Sarasota, Florida
On a suggestion I read this article. Here is a review: Engine Lubrication System Model for Sump Oil Temperature Prediction, Zoz et al., SAE Congress Detroit, MI 2001. The object was to design a model to predict engine temperatures before actual engine development. They used empirical correlations and component models including Flowmaster and ORBIT mathematical models and non-referenced actual engine temperature data for dyno tested V8 SI engines. The paper’s model was of a V8 SI engine with central camshaft and push rods. They showed that 75 percent of engine oil heat gain in wide open throttle, full load conditions, is from the piston undercrown and that 15 percent was from the main bearings. The camshaft was only 1 percent and the oil pump energy was 8 percent. They stated that the oil heat gain from piston-bore friction was not significant. They predicted a decrease of oil temperature of 7 F by using an aluminum vs iron block. Going from an ambient engine cooling temperature of 68 F to 122 F increased the oil temperature 14 F. It was the same for full load at 2,000 or 4,000 RPM. Increasing the ambient air temperature 86 F only increased the oil by 14 F at wide open throttle. The model predicts that the addition of oil squirters to each piston would increase the oil temperature by 25 F. It would result in a piston undercrown temperature reduction of 135 F. (Most high performance engines have atomizers at the base of each cylinder.) They compared their mathematical model to real engine data. The conclusion of the study was that the test model accurately predicted oil sump temperatures. It would be useful as a preliminary design and engine evaluation tool. Critical Analysis: I will assume the Flowmaster and ORBIT models are widely accepted as realistic and that the real engine temperature data was accurate. Noteworthy is that the oil pump energy heat gain was 8 percent. Hence the trend to decrease oil pump size in newer engine development. I would think this goes along with the trend of using thinner oils as they have better flow from less viscosity and lesser internal friction than thicker oils of the same type. Thinner oils and smaller pumps will decrease engine load and temperatures and increase efficiency. The difference of ambient temperature of 86 F only resulted in an oil temperature difference of 14 F. This was at wide open throttle. The difference would be less for lesser loads. This goes along with the lack of oil temperature difference in my Ferrari oil with ambient temperatures in the 40 F to 100 F range. They pointed out that the model was based on heat transfer coefficients and not oil flow rates. Future model development was expected to be in the areas of oil flow rates, bearing clearances and oil flow splits though engines. This shows that these are additional areas of concern regarding engine development. Overall I liked the study and added it to those I will keep and read over. aehaas
 
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3,593
Location
Outside smalltown, IL
In vehicles I've had with water cooled engines and oil temperature gauges I've also seen little difference in oil temps between summer and winter. That's why I've always questioned using different weight oils for different seasons...
 
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40
Location
Connecticut
quote:
Originally posted by jsharp: In vehicles I've had with water cooled engines and oil temperature gauges I've also seen little difference in oil temps between summer and winter. That's why I've always questioned using different weight oils for different seasons...
Really? My observations are quite different. The A4 2.8 I've been flogging around shows 15-20F cooler below 30F ambient, and more when OAT is single digits.
 
Messages
3,593
Location
Outside smalltown, IL
quote:
Originally posted by BenDarDunDat:
quote:
Originally posted by jsharp: In vehicles I've had with water cooled engines and oil temperature gauges I've also seen little difference in oil temps between summer and winter. That's why I've always questioned using different weight oils for different seasons...
Really? My observations are quite different. The A4 2.8 I've been flogging around shows 15-20F cooler below 30F ambient, and more when OAT is single digits.

Actually, we're seeing about the same numbers. I just used "very little difference" to describe it. Less than 10% to me doesn't seem all that significant given the large change in ambient...
 
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