I need to keep an eye on this to have anything definitive to report, but it happens I leave the secondary screen on "auto info" when I'm just driving around town. The bar graphs and numeric data duplicate the analog presentations of course, but they catch the eye and I noticed something interesting tonight. The oil temperature rises very slowly.

Three miles from home, and the oil temp was still 47° F. The water/coolant temp was up to 110° or something like that. As a first guess, the new thermal management mods are piping the heat to the components critical to emissions testing in the start-up phase. That's always been a bugaboo of course. I'm still thinking about this because I'm not sure I see how that guess explains it completely.

No stumbling or anything of the sort. Nothing we conventionally complain of with "cold-blooded" engines. Just a startling number to see from an engine that has been running for five minutes and carrying the car along with moderate briskness. Looks like no fun times at the freeway on-ramp until warm weather returns unless I want to make a five-mile detour to let the engine come up to working temps first.

Gary

 

How do the different fluids circulate?
Isn't coolant typically regulated by temperature, while oil is pressure-controlled? When cold, isn't coolant circulated much more slowly than oil? I would expect that when cold the coolant circulates very slowly, in order to improve warm-up time. When cold, coolant flow could be so slow that coolant in the radiator is cold even though coolant leaving the engine (which I presume is where the temp is read) is hot. Coolant temp reading is much higher than the temp average of all the coolant in other words. Oil on the other hand, well we don't allow oil to stop circulating just because its cold. So all the oil is always circulating and the reading is much closer to the average temp of all the oil in the system. In other words the oil temp will tend to lag the coolant temp. In that case, if the engine's warm enough to be putting out normal operating temp coolant, then it should be warmed up- or darn close to it.

 

Water temp does rise much faster than oil temp in my 991. I don't run it hard until oil temp is up around 195 to 200. I am probably naive; this is my first dry sump car so I assumed it took longer for the oil to come up to temp due to that, and the fact that the sump holds a lot of oil. I also have my screen set to the bar graphs, at least until it is fully warmed up.

 

It warms up faster in Normal mode. With Sport mode engaged, it warms up slower and is held to 200F instead of 225F.

 

It really depends on where they've located the sensor, I'm pretty sure the 991's must be after the thermostat for the oil cooler - wouldn't worry too much about cold temp oil flow with synthetic anyway.
I've also noticed the car will recharge the battery after a cold start at up to 15.1 volts until fully charged and then drop rapidly to 13.8 volts. Overall, these electronc engine management upgrades seem to work very well (as they should)!

 

Oil temp does take forever, but so did my 997. Is the feeling that the 991 takes longer for the oil?

Obviously, the water is much quicker in the 991 -- which a to a dummy like me would seem logical to maybe have some quickening effect on the oil, too. But no.

 

I read somewhere that full operating oil temperature is not achieved until approximatley 6 miles of driving. This seems a rather long time.

 

Neither my 997.2 S or my Cayenne V8 (which has the same "info screen" bar graph options for engine temp etc. that Gary refers to on his 991) are anywhere close to full operating oil temperature in 6 miles, especially this time of year. I haven't done a timed check but off the top of my head I'd estimate it takes twice as long to reach 200-210 on the oil temp gauge versus the water temp gauge.

Interesting topic, Gary. I'll pay more attention to the exact mileage next time I drive my cars.

 

Makes total sense to me. Except, phrases like "it warms up faster" are over-simplifying: what warms up faster? The oil? The coolant? Or the engine?

These used to be all the same, but not any more! A lot of this can be figured out just by looking at info on porsche.com and thinking about how engines work. Then even the Sport/Normal observation makes sense.

 

At 32 degree ambient temperature it can take over 12 miles for the oil temp to reach 170

 

I was referring to the oil temp displayed on the graphic. Coolant temp seems to rise much faster, but it is pretty constant at 200F on my car no matter what.

I read that in Sport mode, the car engages a more aggressive fan effort to keep the oil cool. This also decreases fuel economy, altho I am not fully certain as to why.

 

Really? Since upshifts are delayed and revs are kept higher in Sport mode I would have expected the opposite. Must be something exclusive to the 991. Any idea as to the reason for this behavior?

Edit: Just saw your post about the fan. Still, I would think the fan would be linked to engine temp. Since fast warm ups are good for emissions the fan programming, if true, shouldn't kick in until the engine was fully warm.

 

This thread has some info (or at least theorizing) about the different oil temps/mapping between modes.

I did try mine the other day, and the oil temp drops for sure when Sport is engaged.

http://www.6speedonline.com/forums/9...peratures.html

 

I think I read somewhere that in normal mode the oil bypasses the oil cooler so it heats it faster, and in sport mode it runs through the cooler all the time.

 

Interesting post. I guess I would ask you guys what temps (oil/water) are best before high revs.