Cold-Blooded Engine it seems
Thread Starter
Rennlist Member
Joined: Dec 2009
Posts: 1,429
Likes: 15
From: Southern California
Cold-Blooded Engine it seems
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
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
Race Car
Joined: Jun 2012
Posts: 4,522
Likes: 63
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.
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.
Instructor
Joined: Jun 2012
Posts: 144
Likes: 0
From: N.E. Ohio
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.
User
Joined: May 2003
Posts: 1,043
Likes: 225
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)!
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)!
Three Wheelin'
Joined: Feb 2012
Posts: 1,458
Likes: 233
From: SF Bay Area
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.
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.
Trending Topics
Rennlist Member
Joined: Jun 2001
Posts: 12,988
Likes: 1,442
From: North Bay Area, CA
Interesting topic, Gary. I'll pay more attention to the exact mileage next time I drive my cars.
Rennlist Stories
The Best Porsche Posts for Porsche Enthusiasts
9 Features and Characteristics That Only Porsche People Understand
Verdad Gallardo
I've Written 500 Rennlist Articles: Here's How Porsche Has Changed Along the Way
Joe Kucinski
10 Most Unnecessary Porsches Ever Built (And Why We Love Them)
Verdad Gallardo
Porsche 911 GT3 S/C vs 718 Spyder RS: 10 Categories, One Winner
Joe Kucinski
This Builder Is Turning Heads With Its Slantnose 911 Creation
Verdad Gallardo
Porsche 911 GT3 Artisan Edition Pays Homage to Japanese Culture
Verdad Gallardo
Porsche Reveals Coupe Variant of the Electric Cayenne With a Fresh Look
Verdad Gallardo
10 Porsche Colors That Have More Personality Than Most People
Verdad Gallardo
Guntherwerks' Final Speedster Creation Is the Ultimate Porsche Restomod
Verdad Gallardo
Race Car
Joined: Jun 2012
Posts: 4,522
Likes: 63
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.
Instructor
Joined: Jun 2012
Posts: 113
Likes: 0
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.
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.
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.
Rennlist Member
Joined: Jun 2001
Posts: 12,988
Likes: 1,442
From: North Bay Area, CA
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.
Three Wheelin'
Joined: Feb 2012
Posts: 1,458
Likes: 233
From: SF Bay Area
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 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
Race Car
Joined: Jun 2012
Posts: 3,628
Likes: 346
From: Maryland USA
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.
