GrandPaJohn

I tow a lot and often concerned about rising oil temps. I was curious why the coolant never varied form 200F and I learned that the stock gauges don't give real results. So I plugged in the Foxwell NT530 and the temp readings for both coolant and oil differ greatly from what is shown in the gauge cluster. Do the gauges and the Foxwell read the same sensors or are there different ones? Which reading is a more accurate measurement for my high temp concerns?

BCeagle08

The dashboard gauges do not show exact readings because the fluctuations would scare/distract drivers. They only display whether the temperature is in the normal or abnormal range.

nathan1

This is a known phenomena.... Porsche (and other manufacturers frankly) realize that the average consumer is a mindless idiot who feels warm and fuzzy when their gauges never move.... So they program them to always show a comfortable number unless they exceed that by a wide margin. Now for the digital readout, oddly enough they program the oil temperature to read too high and it gets exponentially higher the higher the temp. So for example on my CD it might show 210F oil temp on the display and a scan tool shows 215F, not a big difference, but when my display shows 270F (scary) actual is usually in the 230F range. When towing I keep my bluetooth scan gauge hooked up and watch it that way if I am concerned. Water temps always read closer to accurate display vs. scan tool.

GrandPaJohn

Interesting. I'll have to use my scan tool next time I tow. Not sure I understand your last sentence. Are you saying the cluster gauge reads coolant temp more accurately than a scan tool? Seems odd since it's usually pegged at 200F.

BrewDude

Your scan tool will read more real time temps than the gauge cluster ever will.

Coolant temp will stay at 200 even if it's not at 200. The gauge electronics are programmed to not be linear, and by the time temps start creeping up beyond the threshold and show things too hot it's usually too late. You'd most likely see a swing of up to 30 degrees on your scan tool and the cluster will still be sitting at 200 degrees.

I had the cluster in my R32 changed to a linear reading and shows real time temperature of the coolant at all times. You'd be surprised how much it swings and would probably cause the average driver a coronary to see it creeping towards the redline.

nathan1

There are two "dash" temperature readings, the physical gauge and the digital display you can toggle to. The physical gauge literally NEVER moves unless you have an absolute crisis (too late). The digital readout will vary slightly but it still is not accurate (programmed that way from Porsche). The scan tool is accurate for actual temps.

GrandPaJohn

UPDATE; So just got back from a short trip towing the trailer. This time I hooked up my OBD2 scanner and compared the coolant and oil readings to those in the cluster. No hills, just flat roads but I was able to confirm that the cluster is way off. Coolant didn't fluctuate much and stayed within 195-210F even though the cluster read 200F the entire time. . The oil temps were the real eye opener....the cluster read from 10-23 degrees higher than shown on the scanner. At one point the cluster read 245F and the scanner showed 222. So I might not have as big of an oil temp problem as I thought. Have a trip in a few weeks that will take me through WV so I'll be able compare the temps when climbing the hills. Thanks everyone.

e92BMW///M3

Interesting feedback. I understand smoothing the temps but does anyone know an approximate range/methodology that the Cayenne is smoothed based on to determine what gets displayed?

ledbette

Porsche aggregates the transmission fluid temperature in with the oil temperature on the Boxster. I wonder if they do the same on the Cayenne.

GrandPaJohn

Latest update...climbing long incline while towing my ~6000lb travel trailer on route 68 in WV, oil temp in cluster reached a high of 264F, but scan toll read 230F. Incidentally, coolant temp stayed within 5 degrees of 200F.

ledbette

Next time it would be good to look at the transmission oil temp and transfer case oil temps if those are available.

Mr Beau

During street/highway driving, my 2011 CT shows 90C / 194F for coolant and oil on the digital gauge readout. Pushing the sport button drops oil by about 10C.
My 2013 CS shows 90C for coolant and 100C for oil. Pushing sport drops the oil temp by about 10C.

Is the non-turbo set to run hotter oil than the turbo under normal conditions or is there something else going on that I should investigate?