Water Temperature

[barryb]

Hi

 

Since I've had my car the water temperature gauge has sat at just over 80°C as one would expect from an 83° thermostat. As my previous post I have just changed my water pump and thought that as recommended I would change to a 71° thermostat. I've driven the car for few days now and the thermostat still sits at just over 80°. There is a common belief that the gauge is just an idiot indicator and does not reflect the true temperature it's either cold, normal or overheating. When I have some time I will check the temperature via the OBD, but it just makes you wonder.

Barry 🤔

[extanker]

I don't know about po cars but putting a low temp stat in other cars requires the fans to be re-programmed [if they are run by the ECM ] 

[Aaron]

The thermostat opening earlier does not necessarily mean a lower engine coolant temp.  The ECU will target a specific ECT as its defined operating temp and only engage the fans when the EGT exceeds a certain temperature.  The fans would then cutoff once that lower temp was reached.  Only if the radiator system was over engineered would you get lower than target ECTs - the engine is producing less heat than is expelled by the cooling system resulting in a lower than expected operating temp.

 

Remember that the purpose of the thermostat is to decrease engine warm-up times by keeping the coolant localised to the engine and only utilising the radiator when coolant temps become excessive - triggering the thermostat.

 

The 987 is a pretty hot running engine but a lower temp thermostat is not really useful for road driving... If your radiator fans never come on generally, then the lower temp thermostat is going to do little more than increase your engine warm-up time.

 

As for the accuracy of the gauge itself - I have no idea.  Reading the sensor output from the ECU is the best way to obtain an accurate reading as you mentioned.  However, if you have never captured the reading prior, then you don't actually have any comparison data to understand whether the thermostat has made a noticeable change.

[MartinF6]

Gauge in a 987 is heavily buffered.

 

It will sit in the same place in the centre across a very wide range of temperatures. Think it has to get well over 100 before it starts moving beyond '80'. It also hits '80' before it's actually 80. I would not expect to be able to see on the gauge whether the engine running cooler due to the stat.

[barryb]

Hi

 

That's what I thought re. the gauge. The ECU does not need reprogramming as the fans will come on when the engine temperature/ coolant temperature reaches around 97°C regardless of which thermostat is fitted as it is a mechanical device with no connection to the ECU. Manufacturers have found that running higher engine temperatures helps to pass emission regulations ( my Mini JCW runs a thermostat at over 100° with the temperature gauge reflecting this high temp). A lot of more knowledgable people than me have shown that a 71° thermostat helps to even out the temperature through the engine especially during warm up helping to limit hotspots and maybe maybe borescoring. 

Barry

[wtaite01]

On 23/03/2022 at 18:00, barryb said:

Hi

 

Since I've had my car the water temperature gauge has sat at just over 80°C as one would expect from an 83° thermostat. As my previous post I have just changed my water pump and thought that as recommended I would change to a 71° thermostat. I've driven the car for few days now and the thermostat still sits at just over 80°. There is a common belief that the gauge is just an idiot indicator and does not reflect the true temperature it's either cold, normal or overheating. When I have some time I will check the temperature via the OBD, but it just makes you wonder.

Barry 🤔

 

On a very hot track day last year I did manage to make the dashboard temp gauge nudge slightly above 80°C but didn't trigger any warnings. That was with OBD coolant temps of >110°C. 111°C was the max I saw before coming in.

 

I am wondering if my Zunsport grills were the issue, will remove them for track days from now on and see if the issue returns.

Edited March 25, 2022 by wtaite01

[barryb]

Hi

 

I guess that confirms the temperature gauge is bit useless. I assume the fans came on at 110°. I wonder what would make the gauge go to end scale,  would the engine have seized by then? You would think like other manufacturers the indicator would give a true representation. That deficiency extends to not having an oil pressure/ temperature gauge as standard, this after all is a performance sports car.

 

Barry

[Neil_jdmr]

This was a common issue with rx7s. The temp gauge wasn't linear so the needle didn't move until your seals were boiled alive then it shot up quite quickly.  

The common benchmark was if your needle moves up at all from average,  shut it down.

 

One modification was to recalibrate the gauge with a replacement sensor. A new gauge and sensor was the easier option but every rx7 runs an aftermarket ecu so you usually get that data displayed anyway. 

 

You could also remove your water gauge and swap it for a stack item in the original cluster. 

[extanker]

If this is a street driven car the factory gauges are sufficient,if it gets some hard track time, invest in quality gauges . 

[barryb]

Hi

 

Why would you not expect a gauge to tell how it is. If it doesn't why have it. If for instance the fuel gauge always showed half full it would be useless as you would not know when you were going to run out. Wether you tear around a track or drive on the street it is reasonable to expect a high end sports car to have reasonable instruments telling the real status of the engine. My old 911 has a set of instrument giving me the information I need to react to developing problems. Modern car makers are starting to treat us like idiots unable to process detailed information. Just my opinion.

 

Barry

 

[extanker]

1 hour ago, barryb said:

Hi

 

Why would you not expect a gauge to tell how it is. If it doesn't why have it. If for instance the fuel gauge always showed half full it would be useless as you would not know when you were going to run out. Wether you tear around a track or drive on the street it is reasonable to expect a high end sports car to have reasonable instruments telling the real status of the engine. My old 911 has a set of instrument giving me the information I need to react to developing problems. Modern car makers are starting to treat us like idiots unable to process detailed information. Just my opinion.

 

Barry

 

is this your first car ?

[barryb]

Hi Extanker

Thank you for your input, it is always good to get advice and help from a knowledgable forum member. Are you a racing driver or a Porsche mechanic perhaps, or just an enthusiast like myself?

Barry

[MartinF6]

23 hours ago, extanker said:

If this is a street driven car the factory gauges are sufficient,if it gets some hard track time, invest in quality gauges . 

 

I would disagree. 

 

Showing the actual temp allows you to see if the car is running abnormally in the early stages of a fault and could help you avoid a catastrophic failure.

 

For new cars run under warranty by the average consumer, it makes sense to buffer the gauge. The manufacturer doesn't want people bringing cars is for non existent faults because an owner sees the temp needle moving about. Better that it seems like the car is always running at the 'perfect' TDC temp unless it gets very, very hot.

 

For us lot running these cars out of warranty, much better to be able to actually see what is going on.

[extanker]

22 minutes ago, MartinF6 said:

 

I would disagree. 

 

Showing the actual temp allows you to see if the car is running abnormally in the early stages of a fault and could help you avoid a catastrophic failure.

 

For new cars run under warranty by the average consumer, it makes sense to buffer the gauge. The manufacturer doesn't want people bringing cars is for non existent faults because an owner sees the temp needle moving about. Better that it seems like the car is always running at the 'perfect' TDC temp unless it gets very, very hot.

 

For us lot running these cars out of warranty, much better to be able to actually see what is going on.

feel free to load the A pillar and top of the dash with a bunch of exact after-market gauges ,maybe a group buy with the op. 

[extanker]

4 hours ago, barryb said:

Hi Extanker

Thank you for your input, it is always good to get advice and help from a knowledgable forum member. Are you a racing driver or a Porsche mechanic perhaps, or just an enthusiast like myself?

Barry

#1 raceD drag,road,off road,still play on the street

#2 re-tired shop owner ,fortunate enough to not have to work on my cars anymore 

#3 over 30 years of racing corvettes,,,,it was time to slow down so i went with porsche ......over priced n under powered lol

[Aaron]

I feel this thread de-railing.

 

I think we can all agree that cars are designed for a specific audience and compromises/decisions are made during that process to achieve the best outcome for the manufacturer - whether that's reduced cost, less needless service questions, or just trying to provide a good driving experience.  No one on this forum designed the Cayman and discussion on those decisions seems a bit moot, especially when the topic is something as specific as target ECTs or reducing hot spots.  As much as I love the technicalities and understanding how things work, I don't have an engineering degree in thermodynamics so I leave that to better trained individuals.

 

If you want a car to have track/race functionality then you need to buy one that's oriented that way, or modify your car to fit that usage better.  There's a great race build thread on here somewhere - it's a great read.  Or, if you just want to vent, then feel free to do so.

 

Personally, I would focus more on driving the car rather than fixating on ECT.  It's much more fun that way.  Especially with the weather we're currently experiencing!

 

[MartinF6]

1 hour ago, extanker said:

feel free to load the A pillar and top of the dash with a bunch of exact after-market gauges ,maybe a group buy with the op. 

No interest in doing that at all. Buffered gauge isn’t the end of the world.

Would just be preferable if it wasn’t buffered, which it wasn’t on the previous gen 986 and 996 cars. You lose worthwhile info, nothing remotely controversial about that.