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I posted this over the winter on that other forum... I saw the posts on warming up a 911 so I thought I would post this here as well.
Nerd Alert!
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.
That's interesting, especially the third point, ie, that the temps rise regardless of load. Any idea why?
First, this is all my conjecture.... FWIW.
I suspect the car has quite a bit of cooling capacity given it is touted as a track-ready vehicle. I believe the engineers are using this capacity to manage thermal growth in a very linear way... they don't want the car to heat up too fast... I suspect they want the other components to warm up along with the engine core limiting thermal differences between components.
Of course, I suspect if I started it and then immediately ran to red line up a steep hill, I could make it run up quickly, but I just followed the owner's manual and drove it normally (actually conservatively for me) and kept the revs down. Looking at the data, I can't really see the effect of my running up the revs or sitting idle at stop signs in the slope of the heating curve. If there is, it is not much at all.
You're probably correct. With as much oil as these cars hold, that's gotta build in a lot of thermal stability. I'm lucky, living in Miami, as I never need to pay much attention to the water temp (unless it's really hot and I'm stuck in traffic. Even then, it's never been an issue.) I watch the oil temp though I'm still learning why.
It's no fun collecting and sifting through data like this. Thanks for doing that heavy lifting!
Interesting, my coolant temp gauge is so steady at about 175 , no matter the outside temp, traffic etc, that I thought it was a very inaccurate gauge. Now your data tells me differently.
Interesting, my coolant temp gauge is so steady at about 175 , no matter the outside temp, traffic etc, that I thought it was a very inaccurate gauge. Now your data tells me differently.
I agree, I think the the thing has gobs of cooling capacity and is just good at it.
Some have made the comments that the gauges tell you want Porsche wants you to see and not what the truth is..... I am not so sure about that.
Another issues is where the heck are these sensors located? Intake to block? Discharge from block? If they obtained the data say inches from where the water had just passed around the combustion chamber, I suspect you would see fluctuation.
The other frustrating issue is Durametric..... the darn thing shows a bunch of water, air, and oil temp buckets some of which return nothing, some return bizarre character strings, some ... well who knows what comes out of there and there is no documentation whatsoever on this stuff.
But it is all quite entertaining isn't it!
One other interesting data point: back when I obtained my 2009 C2S, I had myself convinced that I needed a lower temp thermostat..... please let's not get into that bucket o'worms..... but I just did. So I contacted a supplier and he told me two things: 1) With the 997.2 DFI engines, Porsche lowered the operating temps making the value of a lower temp stat less necessary, and 2) They didn't make them anyway as you can't just swap them out.. Update: Either I am wrong or the guy I talked to was wrong but the DFI engine uses a old-fashioned stat.... part number: 9A1 106 225 01...an 80C (176 F) model. Just google it. I found it in my PDF of the PET parts diagrams.
So, am I right? Did the guy I talked to know what he was talking about? Who the f knows........ I kinda liked the old days when big personalities like my dad wearing a blazer, a drink in one hand, a cigarette in the other, booming out dirty jokes knew everything. The louder and bigger you spoke, the righter you were!
Peace
Bruce in Philly
Last edited by Bruce in Philly; 05-18-2015 at 07:16 PM.
05-17-2015, 04:05 PM
