Re: Warm Up of Water & Oil Temps - Durametric Data

Nerd Alert!

2009C2S 74K miles

Using my Durametric, I tracked the following from a cold start (ambient temp was 32 F):

RPMs
Car speed MPH
Engine Temp (water temp but Durametric shows as “engine”)
Oil Temp
Catalytic Converter Temp

Why did I do this? Um, I dunno, ‘cause I am a nerdy geek. But I, like others, have wondered about oil temps on cold start ups. It appears on our gauges that oil temps lag way behind water temps. But as the graph shows, oil lags water temp by only about two minutes and track closely together. So some observations:

1- Oil temp lags water temp by about two minutes but warm up equally together
2- Oil temps and water temps stabilize to about the same temps under “normal” non-aggressive driving
3- Oil and water temp rise at a controlled constant rate regardless of load/RMPs/speed
4- You can “hit it” after about 10 minutes of easy driving (starting out at 32F) as oil and water temps are near their stable maximum.
5- I did this earlier this winter and witnessed the same, linear controlled rise in water temps under a different driving situation (I did not track oil as the Durametric tool had me a bit confused)
6- Cat temps made no sense to me except they get hot fast and then seem to drift without much regard to other dynamics

Driving situation: Car was kept outside over night and I started it about 10:27 in the morning when ambient temp was 32 F. I waited until the car’s pitch changes (about 20 seconds) and backed out of my driveway. Then I drove gently through stop signs, up a few rather steep short hills, then to a few red lights, and then onto the interstate at 10:37. I kept RPMs below 3500 until I hit the interstate.

Time: Elapsed from engine start to stabilized temps was about 12 minutes and I shut down the computer after about twenty minutes.

Air Temperatures: I did not display any air temps in the chart. Ambient temperature was 32 degrees F. I tracked a few different “Air Intake” buckets and while one sensor tracked between 32 and 34 degrees F (obviously external, ambient temp), others were very different although they all started out at 32 F. One swung from 32 F to a high of 193 F and tracked closely with vehicle speed and RPMs dropping to 32 F when vehicle speed was 0.

Catalytic Converter Temps: I recorded both left and right bank but showed only the left in the graph, as both read virtually the same.

Peace
Bruce in Philly

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In some ways it confirms my suspicions (e.g.: temps warm up a bit faster than the likely damped gauge shows), and oil lags water. I would haev expected it to lag more however, and this is, i think, good news.

If you have another nerd attack, i'd be curious to see how fast oil vs water cool. On my Audi, where i can monitor such things, it appears that the water will lose heat rapidly, but the oil will hold it for many hours.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The coolant temp curve is very similar to the ones I've seen from the data from my cars. I have no way to pull oil temperature or converter temperatures from the vehicle. (I'd have to custom code something up and I've never had the time.)

Just a word of caution. While coolant and oil temperatures are at nominal operating temperature not all oil is warmed up (and maybe not all the coolant either.) There can be some oil in the sump that believe it or not is really not in circulation and still relatively cold. A large increase in engine RPMs will of course result in a big demand for oil. At this point the oil off to one side of the oil pump intake will get drawn in and this is much colder oil. Granted there is not much of it.

With other cars I have observed the coolant gage needle climb to the point the engine coolant is up temperature but more than once have observed the coolant temperature drop some as the T-stat fully opens and lets a slug of colder coolant through.

Now with my Porsches I've never really seen the coolant temp take a dip or a drop nor have I observed any drop from the actual coolant temperature data. It would appear that -- better be sitting down for this -- Porsche has this engine warm up business pretty well sorted. That somehow it manages to avoid large temperature gradients in the coolant as the engine/coolant warms up.

Before I push the car hard, the engine hard, I always of course drive the car easy until the coolant temperature gage needle is at its "usual" engine operating temperature point on the gage face but I then continue to drive the car still easy (but not as easy as I drive with things dead cold) for some minutes more. I want to give the entire load of coolant and oil time to get fully up to temperature.

One fluid heats the other at first, then the "direction" is reversed and one cools the other. Can't find the information source, so no verification is offered here concerning which is doing what when, but it was part of a technical description for the 981. May apply to the 986 and 7.

Quote
MarcW

Just a word of caution. While coolant and oil temperatures are at nominal operating temperature not all oil is warmed up (and maybe not all the coolant either.) There can be some oil in the sump that believe it or not is really not in circulation and still relatively cold. A large increase in engine RPMs will of course result in a big demand for oil. At this point the oil off to one side of the oil pump intake will get drawn in and this is much colder oil. Granted there is not much of it.

You may have hit on why there is a lag in the oil gauge.... there may not be. If they are pulling the temps from, say the sump or at the pump where it just came from the sump where hot return and the cold pool are mixed, then the oil will read cooler than the water..... there is your lag. I am assuming, I think correctly, that water turnover is faster than oil turnover.

Regarding the coolant... many years ago I ran the engine in my Buick with the radiator cap off and I was amazed at the amount of swirling going on. That water pumped moved some volume. If all cars move water at that rate, there would be consistent temps throughout the coolant volume.

Another variable is how many places does Porsche track a fluid's temps and what do I tick off in the Durametric tool to see them? The tool now has about 4-5 different line items that say "Oil Temperature" but only one will provide values. The sensor feeding the gauge may not be the sensor I am reporting out here. The Durametric tool has virtually no documentation on what the tracking buckets actually are or where the senders are located.

It just doesn't make sense to me that Porsche would go through the expense of creating a laggy oil temp gauge just to mislead us. If the rest of the engine or oil must warm up, then fine, state the OK oil temp in the manual or put a green line directly on the dial. Or, like some manufactures do (BMW so I've been told), limit your RPMs until OK temp is reached. Purposly misleading us is a bot odd...... I've read that there are folks who believe this. Jake Raby noted on more than once that Porsche displays the temps that "they want you to see". Not that I don't believe Jake, but I just don't understand why a maker would purposely dick with gauge readings. I don't see why it would matter.

Peace
Bruce in Philly



Edited 3 time(s). Last edit at 03/31/2015 11:11PM by Bruce In Philly (2000 S Boxster, now '09 C2S). (view changes)

My 986's coolant gauge would read to whatever the temperature was, no matter how high, although there was no oil temperature readout available in the settings options. (Hmmm, were there any?) When I first got the 981 in June 2012, the gauge would read only to a maximum of, IIRC, 214 F. (Early on I didn't think this was a capped reading and wondered how Porsche could keep the temperature so stable! All that "thermal management" I guessed.) Apparently, as delivered, Guenter's was capped at 194, and after a software update sometime in the last year or so, mine reads only that far, too. Having a cap makes no sense to me, and as someone once mentioned here, in an overheating situation, you won't know until a warning light comes on. My workaround, which I actually set up when I first got the car just to have the information, is to have the multi-function gauge read oil temperature (and pressure.) If anything, the oil readings are giving you some idea as to what's going on with the all-important internal moving parts.