Eh everyone,
Just wondering what the normal operating temperature is for our cars? When I had my 84, It was always hovering around the first white line...
Right now, my car has the 3 white lines and the red one, first line is 40 (I am guessing in Celsius?), second line jumps to 80, third one is blank and last is the 100 Red line...
Just wondering if it's normal for the car to jump to the 80 line about 5 minutes in and it usually hovers around between the 80 and sometimes closer to the last white line even only half an hour or so of driving?
I dunno if the display might just be different or if it's sumthin I should be getting checked... the first 'section' is the 40 line to 80 line... second section is the 80 line to the last blank white line and the last section is the last white line to the red 100 line... so technically it's divided into 3 sections on the temperature display...
Any help or info into this would be great... just don't like the idea of overheating and stuff just in case

 

The best way to know for certain is to borrow or buy an infrared pyrometer, the guages all may be up or down a few degrees. I've "shot mine" at the first white line and also at it's normal operating temperature. My guage will usually hover at a 9 o'clock position and shooting the temperature at the thermostat housing it is between 175 and 180 degrees.

Hope this helps, but with the age of our guages and the difference between models this is your best bet for an accurate idea of true engine temp.

Regards,

Ken

 

So hard to tell, as mentioned gauges might be calibrated differently. My 87 S4 lives just below the second white line nearly 100% of the time. Only exceptions are extremely hot Texas days when I am in stop and go traffic. It has moved above the second white line a few times in that situation.
I should really put a temp gauge under the hood just to verify the exact temp.

 

Like jayc67 that was where my 87 temp lived with an 83C thermostat, I changed to a 75C and it runs between the bottom white line (cruise) to a couple of needle widths above the lower white line in traffic.

But if you are really concerned go get the IR readings.

Chris

 

Hi,
during most of the last two years I have randomly monitored my engine's temperatures taking nearly one hundred IR readings on the way. The vehicle had always been run for at least 30 minutes and usually much longer

They are given in this order - median, average, highest, lowest,

Gauge reading: 85, 85, 87, 81 (estimate of reading)
Thermostat housing: 86, 86, 90, 78
Rad hose top: 74, 72, 88, 55
Rad hose bot: 76, 76, 90, 61
Valve covers: 88, 88, 94, 85
Vee: 88, 88, 94, 80 (adjacent to temp sender)
Oil cooler top: 75, 74, 88, 54
Oil cooler bot: 77, 76, 90, 53
AT cooler top: 61, 60, 76, 43
AT cooler bot: 51, 50, 77, 31

Ambient spread: 43C max and -5C minimum - in snow

All IR readings +/- 2C of course

Note:
a ) The bottom hose can be warmer than the top hose due to the integrated oil cooler and the cooling system's "heat sink" radiator
b ) The ATF (Castrol's Transmax Z synthetic) runs remarkably cool in all conditions
c ) Reading temperatures at four key points (say top hose, bottom hose, OC top and bottom etc.) will tell if the system still has any "reserve capacity" when overheating is suspected
d ) The vee & valve covers are good indicators of the engine's actual "core" temp
e ) It takes about 30 minutes to fully warm up a 928 at an ambient around 15C. This may only bring the oil up to coolant temperature (83C+) in very cold conditions
f ) Cold engines should not be revved too high - the OP relief valve cracks at 8 or 9 bar and this is a very high pressure
g ) The oil cooler thermostat's 87C opening point suggests it operates at a late stage of heat management - quite usual in a coolant cooled engine
h ) Using a 75C thermostat in these engines may be counterproductive and I would advise against it

Best of luck

Doug

 

Just drill and tap into the water manifold and install a good autometer temp guage. Thats what im doing. When i get done, and if i remember, i will let you know what line corresponds with what numeric temp.

 

Hi Doug,

I asked Jim B once about running a cooler thermostat in my old S4 and his response was sure you could do it but Porsche set the engine up to run optimally with what they put in 'stock'. Made sense to me.

 

Hi Jim,
of course Jim B is correct but there are others on here that may have a conflicting view. In my experience alloy engines sure lose heat quickly in normal operation. This is especially so in the engine's areas of high air flow and at the extremes where some struggle to keep hot enough
I often wonder how often the 83C themostat opens in very cold weather - say at even -15C - and especially at speed is such conditions - or colder!
There are so many sensors on the engine that are temperature dependent that the variance caused by using a 75C thermostat (an 8C variance) could have a really negative affect on its overall performance

Considering that most engine oil's anti wear and other additives including the viscosity polymers are temperature dependent it will likely have a "spill over" effect there too
I have just completed some work on this aspect of the 928's engine oil and the effect of viscosity is quite amazing and very dependent on getting it up to the oil cooler's thermostat crack point (87C) ASAP

The 928s collective cooling "system" (coolant,air,oil) has enormous capacity - with the S4's first warning being at 118C and the second at 120C. An A3/B3 synthetic oil with a HTHS vis. of 4>cSt will operate up to 130C without too much drama and very little deterioration - if any at all

Regards
Doug

 

Here is a good view of my temp gauge during "normal" operation of the vehicle.


Edit: FYI this was taken July 11, outside New Orleans LA at or near sea level.
AC on full, outside temp right at 100 F.

 

All well and good, but I had two new 83C thermostats that operated quite differently, one would run up by the 2nd white line. The other anywhere from just below centre to the top white line.

If the 928's operating temps need to be spot on somewhere all the time then the thermostat is the weak link.

Didn't Devek post somewhere that 75C thermostats also help pass some of the CA smog tests ?? Reduced combustion temp helps one of the readings I forget what.

Chris

 

From what I have seen here, the S4 cars run warmer than the older ones. When pushed hard or an a racetrack, mine will run nearly to the red. The radiator is new, everything is working properly and I have never experienced ill effects from running warm. I don't think what you are seeing is unusual.

 

Once tried the 75C version........engine/oil took much longer to warm up with the car feeling sluggish during this time. Once fully warmed up final operating temp was the same as with the 83C version. My GT loves the 83C version and runs between 180F and 200F during normal operation in all weather......verified by infra-red thermo.......anything less and performance and fuel mileage goes down.

 

Chris, Interesting the diff in the 2 thermostats.

Brent, My S4 always ran near the second white line and over during track days. My GT never gets near the second white line.

Jayc67, Porsche changing to the digital instrument cluster was a bad idea in my eyes. The analogue looks so much better.

 

Hi Chris,
I think that the 928 gauge is a "living" indicator - it is not a surgical intrument. It is certainly not a sanitised device like on most newer vehicles either. These operate via an "invisible" band and sit in one position that may span some degrees. And they sit there from -10C to 50C and don't communicate a thing. They are only reactive outside their operating band when cold or very hot and according to the manufacturer's specifications

Mine gauge sits as per "jayc67's" most of thetime but moves according to a/c use,air flow etc etc - a friendly "living" gauge!

I believe that these engines really do have very good thermostat control - even allowing for variances between thermostats - and the one thing I have learned using the IR reader is how consistent the engines "core' temperature is in normal use cycles. It you look at the median readings for the valve covers and the vee I posted above you will see what I mean. After all this is where the engine's true temperature is

The engine's "83C" thermostat opens at around 83C and is fully open at 98C. The oil cooler thermostat opens at 87C and is probably fully open within about 5C (92-93C) which is about the ideal temp for engine oil. It is likely most 928 engines will operate with a "core" temperature around 88C-95C which is near to perfect and one reason why they last so long

A 75C thermostat will reduce that by 7-9C - in an iron engine it might be an option!

Regards

 

Doug, I respect your opionion you have a lot of data collected and analysed for sure.

At the end of the day its all down to whatever you want to do, great to have a choice.

On the two thermostats one was Wahle, the other Behr ? Can't remember, either way both came from 928intl and both are no doubt

One + for the 75C is that it has the failsafe valve.

Chris