As I've been reading many threads here, one thing I've picked up on was the dumbing-down of temperature readings (ie coolant) at the factory. If they have done this, why bother with a gauge, and just use green yellow and red idiot lights? The gauge is just fluff if it isn't accurately reading. I want and expect the real deal. To have anything less in a $100k car is unacceptable.

My question is this, and forgive me if the answer has been overlooked but, is there a way to circumvent this, and either by oem or aftermarket, have gauges that read true and in real-time? Is is a matter of programming or hardware, or...??
I expect to see exactly what is going on with all systems, and not an approximation or a watered-down message. Thanks!

 

I've never heard that coolant temp was incorrect - what's your source?

 

The coolant temp reads accurately. It is a wive's tale to say that it is wrong. The coolant system regulates the coolant temp very well and that is why it is so stable. Oil temp is a much better param to monitor and that fluctuates more.

 

You are wrong sir. This has been well established and confirmed by Porsche techs. The coolant gauge has a "dead zone" from around 180 F to 215 F.

 

1BlinkGone , I agree that it sucks but pretty much 100% of cars do this now, so we have to live with it.

If you want an accurate temp, you can get it on the OBDII port. I know some people have hooked up the very cool "ScanGauge" device to OBDII and stuck it on their dash somewhere to get realtime accurate readouts.

See for example :

http://www.planet-9.com/cayman-boxst...-accuracy.html

There are also some 996 guys on rennlist who have done this.

 

The PLX kiwi is a self contained broadcasting OBD device - it sets up a wifi link to your ipad or iphone and then REV or Dashcommand can be used to view realtime data such as temp, air temp in, maf, timing advance - very very cool. And I can second the well established fact that 175 on the dash is NOT 175 - typically 189 or so, and then thermostat opens above 190 or so

 

"well established" and "confirmed" whom?

 

cbzzoom, DUnkleblau S...
THANKS! This is great news. Wish it could be done on the car's existing hardware, but this is quite acceptable if not. Cool beans.

 

You could find it easily if you did some searches. I gave you one link already, but I'll provide a few more so that future readers will find the facts more easily.

Just on the 997 board :

http://forums.rennlist.com/rennforum...il-temp-2.html

http://forums.rennlist.com/rennforum...er-what-2.html

http://forums.rennlist.com/rennforum...-anyone-3.html

There are even more at planet-9 and on the 996 boards ; there are also lots of posts involving LNE and the low temp thermostat where people take actual coolant temp measurements.

 

I would agree with those stating that the water temp gauge reading is not accurate. My car reads 175, no more no less, regardless of oil temp, winter, summer, -20 or +100, with the AC on or off, in traffic or stopped in traffic. No way the cooling system is so well engineered that the cars water temp would never waver by a single degree once warmed up regardless of the ambient temperature. If Porsche was that technically adriot they would have fixed the RMS problem years ago.

 

Thanks for the links...I always appreciate more information and I'm familiar with some of these posts since I see my name in one from a couple of years ago. I still have a difficult time characterizing this information as all factual...and even if it were, I'm not sure what the issue is. My guage tells me when the engine coolant is at operating temperture (whatever that is) and tells me if it's getting too hot. I actually judge my engine temps more from the oil temp guage than the coolant temp. I just don't think the info is that cut and dried to call someone else's response "wrong". To me RMS failures are an issue, not a temp guage that may or may not reflect the true coolant temp...but we're all entitled to our opinions.

 

It would take determined design action to design such nonlinear behavior. I have seen my temp going up from the 180F op point under the appropriate conditions.

I did not see in the links you posted any authoritative statement saying that the coolant temp gauge does not work. Quite the contrary:

Edgy01: "According to my service manager the gauges do actually work. They have seen them venture above 175F but only when an engine lost all its coolant. So, it truly is a temperature gauge and reports what it is experiencing, and not merely pegging at 175. Once again 1999Porsche911 makes a claim but then never backs it up with proof. I don't know why anyone reads this stuff from the self-professed oil and coolant 'expert.' He never cites his experience but is quick with the analysis. He's never opened up a 997 engine either."

and OCBen states it well - it's the oil temp you should be looking at:


"Originally Posted by 1999Porsche911: 'Engine temperature is the same as coolant temperature.'

No, engine temperature is not the same as coolant temperature, unless that's a jargon convention used among mechanics, even though it would be technically inaccurate.

An engine has many thermal gradients throughout the engine block. At the cylinder walls, piston caps and heads where the explosions of combustion take place, the temperatures are the hottest - natch. It's the combustion chambers that are the source of heat in an internal combustion engine, otherwise known as a heat engine in engineering parlance. The sole function of the heat management systems in an engine is to get rid of this heat as efficiently as possible.

In a water cooled engine the coolest temperatures are at the coolant inlet where the thermostat is typically located. And if the water temperature sensor is located here - where it typically is - these temperature readings are the coolest temperatures in an engine. From this point on, all temps will be hotter throughout the engine. So we have the hottest engine temperatures at the combustion chambers and the coolest engine temperatures at the coolant inlet.

The oil temperature is generally more indicative of what might be regarded as the 'average' engine temperature, provided no heat exchanger for the oil is being used. And the term 'engine temperature' would more accurately be described by oil temperature. It should be obvious that oil temperature will always be hotter than coolant temperature, since all temperatures beyond the coolant inlet will always be hotter."

The oil temp gauge is a better indication of the actual engine temp. The coolant temp is far more stable and better regulated. But I have seen it change, contrary to the hereby accepted common wisdom. Drive spiritedly up a mountain side for a few miles on a hot day and the coolant temp will surely rise; the oil temp will rise too and faster, as it should be.

 

i have smartycam system that feeds from ODB2 port and indeed 'engine temp' parameter it reads fro it does fluctuate a bit while water temp gauge stays dead accurate in the middle.

 

That is because the coolant temp gauge pickup is in a point where the coolant temp is well regulated. Other points in the engine will fluctuate more. The coolant temp should be seen as a long time average of the coolant temp and that is a good thing, and yes I have seen it vary. For short time averages rely on the oil temp gauge - that's why it's there. Beware also that initially the coolant rises in temp much faster than oil. That's why an engine should not be pushed before the oil reaches op temp.

 

Excellent reading here: http://www.hartech.org/docs/buyers%2...20part%205.pdf

The temp sensor is in a stupid place (closer to the radiator), the thermostat opens too high, and by the time it does (190), the engine may actually be 20-25 degrees hotter - I say again, whats the point in having a gauge on the dash that sits at 175 no matter what --- it becomes clear now, they don't want you to worry about it until it is truly a huge problem --- problem is you don't know what is actually going on in the engine - and now we see scored cylinders in the M96 and M97 engines as a result of uneven cooling in bank 2.

SO, I would say this is a very relevant concern.