I don't get the large temp increase at the bearings, either. If the oil sump temp is 93°C (199.4°F), then a 40-45°C rise would mean 133-138°C (271.4-280.4°F). Even briefly, wouldn't those temps destroy most oils?
Engine Oil Temp Measuring Points
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Given that sump temperature is pretty well the only thing that can simply be measured, that's the "rule of thumb" that has developed over the years.
This is only adding a hypothetical to the argument, in an area that I'm unsure about...it seems pretty coincidental that HTHS and Noack are measured so far above bulk oil temperatures in an engine (and far closer to bearing exit temperatures).
This is only adding a hypothetical to the argument, in an area that I'm unsure about...it seems pretty coincidental that HTHS and Noack are measured so far above bulk oil temperatures in an engine (and far closer to bearing exit temperatures).
Thanks, Shannow.
Brit -
But what will you compare it to? Maybe yours is high or low. You'll never know.
But what will you compare it to? Maybe yours is high or low. You'll never know.
Originally Posted By: Bruce T
I don't get the large temp increase at the bearings, either. If the oil sump temp is 93°C (199.4°F), then a 40-45°C rise would mean 133-138°C (271.4-280.4°F). Even briefly, wouldn't those temps destroy most oils?
Where are you seeing any temp rise anywhere near that high? That would be a huge amout of resistive power loss and need for heat rejection. Where would this heat be going?
When I look at the charts on the link I see a 5C increase.
Unless you are talking about the highest/maximum performance #s on some of the charts.
I don't get the large temp increase at the bearings, either. If the oil sump temp is 93°C (199.4°F), then a 40-45°C rise would mean 133-138°C (271.4-280.4°F). Even briefly, wouldn't those temps destroy most oils?
Where are you seeing any temp rise anywhere near that high? That would be a huge amout of resistive power loss and need for heat rejection. Where would this heat be going?
When I look at the charts on the link I see a 5C increase.
Unless you are talking about the highest/maximum performance #s on some of the charts.
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Sort of back to the measuring....what about an IR thermometer on the outside of a cast aluminum pan? How close would this be to the actual sump oil temp?
Originally Posted By: cp3
Sort of back to the measuring....what about an IR thermometer on the outside of a cast aluminum pan? How close would this be to the actual sump oil temp?
If it's an aluminium sump I would guestimate the IR reading to be about 10C cooler than the oil temp's at the bottom of the pan. A steel pan I suspect would be less than that but it's easy enough to find out if you know someone with an oil temp' gauge equipped car willing to let you take a reading.
Sort of back to the measuring....what about an IR thermometer on the outside of a cast aluminum pan? How close would this be to the actual sump oil temp?
If it's an aluminium sump I would guestimate the IR reading to be about 10C cooler than the oil temp's at the bottom of the pan. A steel pan I suspect would be less than that but it's easy enough to find out if you know someone with an oil temp' gauge equipped car willing to let you take a reading.
With your IR thermometer at the ready, yank the dipstick and read it quick.
Originally Posted By: Jeff_in_VABch
Originally Posted By: Bruce T
I don't get the large temp increase at the bearings, either. If the oil sump temp is 93°C (199.4°F), then a 40-45°C rise would mean 133-138°C (271.4-280.4°F). Even briefly, wouldn't those temps destroy most oils?
Where are you seeing any temp rise anywhere near that high? That would be a huge amout of resistive power loss and need for heat rejection. Where would this heat be going?
When I look at the charts on the link I see a 5C increase.
Unless you are talking about the highest/maximum performance #s on some of the charts.
I think the 45 degree number was from Shannow and stuff he does with turbine bearings, not from those charts in the linked document. I haven't had time to sit down with that info yet bit it's clear from a brief overview that the bearings run hotter than the sump, even more hot as rpms increase. It's also clear that the HTHSV spec is at 150C for a reason, perhaps because it's considered the upper limit for most engines.. as 100C KV is considered normal for many engines.
Originally Posted By: Bruce T
I don't get the large temp increase at the bearings, either. If the oil sump temp is 93°C (199.4°F), then a 40-45°C rise would mean 133-138°C (271.4-280.4°F). Even briefly, wouldn't those temps destroy most oils?
Where are you seeing any temp rise anywhere near that high? That would be a huge amout of resistive power loss and need for heat rejection. Where would this heat be going?
When I look at the charts on the link I see a 5C increase.
Unless you are talking about the highest/maximum performance #s on some of the charts.
I think the 45 degree number was from Shannow and stuff he does with turbine bearings, not from those charts in the linked document. I haven't had time to sit down with that info yet bit it's clear from a brief overview that the bearings run hotter than the sump, even more hot as rpms increase. It's also clear that the HTHSV spec is at 150C for a reason, perhaps because it's considered the upper limit for most engines.. as 100C KV is considered normal for many engines.
Jim Allen I think the 45 degree number was from Shannow and stuff he does with turbine bearings said:
Oil in car crank bearings runs hot. 270-300 deg F can be normal.
Can't find my chart.
Can't find my chart.
Generally, bearing outlet temperatures run from 10C to 25C above engine oil sump temperature. The variance comes from bearing design (eccentricity, surface area, etc), oil flow rate, and viscosity. Bearings with less bleed-off or running higher HTHSV oils lead to higher bearing temperatures with125C as the upper limit for ideal temperature. What is interesting, are some graphs in a report I read that implied a linear relationship between increasing hthsv above 2.6 cP and increasing main/rod bearing weight loss.
Found it! Not saying that this is gospel, but I believe it is good general advice:
http://performanceunlimited.com/documents/tempguide.html
My main intent is to show the bearing oil temps vs. pan temps.
http://performanceunlimited.com/documents/tempguide.html
My main intent is to show the bearing oil temps vs. pan temps.
Yes, that's the one. Thanks for reminding us how to find it!
^It's funny the relative 'life expectancy' is limited to 100,000 miles or so under 'good' conditions. It's 1999, so I suppose that's the 'acceptable' expectancy mid-90s? Get 100k and call it a day?
However, the data is probably very accurate as far as relative to 'how to make my engine/transmission last the longest'?
However, the data is probably very accurate as far as relative to 'how to make my engine/transmission last the longest'?
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