Sump Oil vs. Coolant Temperatures

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As some added info, now that I've got a car with an oil temperature gauge I can see how things work a little better.

I also noticed that since I had my cooling fans programmed to be on all the time when the car is at low speeds, not only does my coolant temp never go above 194, but my oil temp now is much more stable too. I saw the oil temp hit 221F when stuck in traffic before I got the fans redone, but now since getting them done, the oil doesn't go much above 205 when stuck in traffic. I took a highway trip yesterday and my coolant temp was 189-190 at 70mph (in 70F weather) and my oil was in the 205-207 range most of the time. Tranny temps were mostly in the 170-180F range by the way.
 
Patman, you might want ot rethink your fans on all the time at low speeds setting. The fan motors have a finite life and last I heard aren't cheap. A compromise at some temp like 205 or 210F would get you most of the benefit with fewer fan motor hours.
 
quote:

Originally posted by XS650:
Patman, you might want ot rethink your fans on all the time at low speeds setting. The fan motors have a finite life and last I heard aren't cheap. A compromise at some temp like 205 or 210F would get you most of the benefit with fewer fan motor hours.

I was worried about that at first too but there are a number of guys I've talked to with LS1s who have their fans set this way and have had years of trouble free service. Keep in mind that once the car reaches about 35-50mph those fans both shut off anyhow, so it's not like they are running for the entire time I'm driving.
 
quote:

Originally posted by rob-the-oil-nut:
Did you change the programming for winter? Or is this a summer-only car?
All the best in 2005
Rob


I haven't changed the programming yet, and I do drive it in winter. The oil temps are still getting into the 190-199 range everyday though, so I think it's ok. I do plan on getting my dyno tune redone though, at which point I'll have the high speed fan set to come on at 200F instead of having it run all the time.
 
From MolaKule's quoted study:
"The Oil Sump temperature is always 1.2 to 1.43 times higher than the coolant temp."

This is why people get misinformation. This bench study was done at WIDE OPEN THROTTLE, full power. We know that at the race track the coolant is at 220 - 230 F and we know the oil sump is as high as 300 F and higher. But nobody drives under this condition and then rarely at the track.

For off track conditions the coolant and sump temperatures are nearly the same.

My Ferrari and Lamborghini coolant and oil temperatures run around 180 - 185 both around town and at sustained 130 MPH speeds. Both conditions are actually low load for these cars.

aehaas
 
MolaKule: One item I would have liked to seen in the heat sources was lifters/tappets. I have read, but have not seen proven, that a roller lifter will generate less heat than a conventional flat tappet. On the surface of things, that makes sense. I just have never seen actual studies done to verify this, or even seen how much the lifters add to the oil temp. If what was listed was all that was shown, perhaps it's not a significant amount.
 
Reviewing again: Engine Lubrication System Model for Sump Oil Temperatures Prediction, Zoz et at., SAE 2001-01-1073.

This was a mathematical model compared to real engine performance on a dynamometer.

In the real V8 the average sump temperature at 2,000 RPM at “road load” conditions was 100 C. At 2,000 RPM and full load WOT the average was 115 C and at 4,000 RPM full load it was 135 C. The experimental model predicted these real life motor figures.

In modern pressurized coolant systems the thermostat begins to open at around 85 C and is fully open at 95 - 100 C. Thus the minimum temperature of the coolant for even “road load” is going to be around 90 - 95 C. At full load, WOT and 2,000 RPM and at full load, WOT at 4,000 RPM the maximum water temperature is still only 100 C.

By increasing the air flow through the radiator and engine compartment the coolant temperatures could be as low as 80 C at both 2 and 4,000 RPM WOT full load conditions. But this is an experimental set up in the dyno lab.

In real life the coolant is always around 100 C plus or minus regardless of the oil sump temperature. Coolant flow rates and air flow rates vary keeping the coolant at approximately 100 C under all conditions. This is true even though oil sump temperatures run between 100 C for low load and 150 C for high load conditions.

aehaas
 
I would like to see how the shown energy distribution into the oil compares with the energy distribution into the water cooling system.

I can understand the large amount of heat disipated by oil on the back sides of the pistons, as evidenced by higher performance vehicles using oil squiters towards the backsides of the pistons.

But there are engine architectures where a good deal of the heat removed at the heads goes into the oil system and not into the water system. The 5 Valve Ferrari F355 and 360 motors use water cooling only for the intake side of the heads and use oil cooling on the exhause side of the heads. Probably due to the difficulty in routing water passages with all those valves and actuation mechanisms.
 
Interesting stuff. Someone please riddle me this:

Say I have a manual tranny car. The car has a "universal" replacement radiator equipped with the lower cooling section normally used for cooling automatic trannys. The section is unused and capped with pipe plugs at the inlet and outlet.

What will be the result of running the engine oil through that say, using a sandwich adaptor?
 
It's been done, but I don't know if there is anough flow available to use it as a full flow setup, but it could work as a bypass. My understanding is the tranny pumps through relatively low foil flows.
 
One of the questions you have to answer is, "How much oil would be diverted via the sandwich adapter?"

Another would be, "Can the oil pump supply enough flow to the rerouted oil AND engine components without significant pressure drops?"

As long as the hoses and system can take up to 75 psi this would be a viable way to cool engine oil. How much it would cool the oil would be dependent upon how much oil is diverted to and through the radiator.

The system would allow oil heating from the radiator and cool the oil when hot.

My '92 Burb had this system and I attributed its longevity (382,000+ miles) to this feature.
 
All my Taurus SHO motors come with oil/coolant Hx at the oil filters. Oil generally stays at or 20F higher than coolant temp.
 
Quote:
This is why people get misinformation. This bench study was done at WIDE OPEN THROTTLE, full power. We know that at the race track the coolant is at 220 - 230 F and we know the oil sump is as high as 300 F and higher. But nobody drives under this condition and then rarely at the track.



This is NOT misinformation.

"The slope for both RPM ranges was about 0.7 C/C, which means that on the average, the Oil Sump temperature is always 1.2 to 1.43 times higher than the coolant temp."

This 1.2 to 1.43 figure was derived from the slope of the curve in this study under specific conditions, and clearly stated "on the average."

Each engine oil/coolant temps will vary depending on the engine design, throttle condition, oil used, and the heat exchanger (radiator) used and the amount of cooling air available.

The simulation did show correlation with the "bench" engine.
 
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Originally Posted By: MolaKule
One of the questions you have to answer is, "How much oil would be diverted via the sandwich adapter?"

Another would be, "Can the oil pump supply enough flow to the rerouted oil AND engine components without significant pressure drops?"

As long as the hoses and system can take up to 75 psi this would be a viable way to cool engine oil. How much it would cool the oil would be dependent upon how much oil is diverted to and through the radiator.

The system would allow oil heating from the radiator and cool the oil when hot.

My '92 Burb had this system and I attributed its longevity (382,000+ miles) to this feature.

That is very interesting, but I think adding a thermostatic switch that opens at a set temp say 85C for the oil, to flow to the cooler would be better, IMHO ?
Then since I have a cooler, I can use XW30 oils instead of the Xw40s I have now. What I am afraid of is, more oil lines, more chances of leakage.
 
I've started using my Volvo 850 as my daily drive...I must get back on my pushbike as it's less than 4km to work, but always find an excuse, and am a bit concerned about the short commute on my oil. It has a trans cooler in the bottom tank and an oil cooler in the top tank - I'm surprised at how quickly this engine warms up, by the time I get to work the thermostat is open, and the sump is too hot to touch. My other cars get up to temp on the gauge in the same time, but the thermostat is still closed. Looks like the oil cooler is bringing the coolant up to temp faster. No overheating, temp is consistant on a trip, just a very rapid engine warm up. Makes me feel a bit better using it on short runs.
 
Originally Posted By: MolaKule

My '92 Burb had this system and I attributed its longevity (382,000+ miles) to this feature.

so in other words, keeping the oil temp relatively low, ..not too low, say 85 to 95C will ensure engine longevity ?
 
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