Curious about this question I collected some data some time ago, for what it is worth.
The title question enters into many a concern related to coolant temperature and this post is my attempt to use VCDS to try and answer this question, at least for my A2, albeit an FSI but this should not matter too much.
The coolant temperature is "read" by the sensor G62 which has two "outputs", one reports to the engine ECU and the other to the dash [& ultimately the temperature gauge].
The temperature value the ECU "receives" and acts upon is easily observed in VCDS from
The other "output" of G62 to the dash of course can be monitored in a way by simple observation but this is subjective. As an alternative I am led to believe the gauge can also be monitored using VCDS under 'Instruments'.
Good that the coolant temperature on this screen is not labelled G62 as in the Engine controller - argues this is the other "output" of G62, and backed up by the curious value of 30℃ which is different to the Engine screen controller above. 30℃ seems some kind of default for a cold engine in Instruments. The dash ambient temperature was 20℃!
The ideal would be to monitor both "outputs" of G62 side by side with VCDS, ready to compare with gauge readings, but I have yet achieve this but if anybody knows how I am all ears. The best I have achieved is to flit between 'Engine' and 'Instruments' controllers forming a log along the way that contains the coolant temperature "outputs" from each side of G62.
In this context the rest of this post is devoted to the warmup of coolant in my FSI from overnight cold with comparison of my manual observation of the dash temperature gauge. I repeated the exercise 5 times on consecutive days with exactly the same trial, the only change was the ambient temperature that varied by a few degrees. The results were broadly in agreement but not exactly the same, the figures quoted below are a representative.
Some points to note first ...
1. For other A2 models I expect only the range of values will change (& the time to achieve these but no emphasis is placed on time here).
2. The exercise was "driven" by observation of the dash gauge. When I judged the gauge needle was bang on the calibration points of 60, 70,80,90 ℃ the two VCDS temperature values were logged.
3. The VCDS values in (2) are not at the same point in time, it took about 25 seconds to flit between first 'Instruments' and second 'Engine' controllers to log the temperature values
4. As a matter of safety I did not wish to log VCDS values while driving. Not to annoy my neighbours I parked in a nearby quiet country spot with engine idling for some time and this invoked the curiosity of several passing dog walkers - I wondered if they thought I was committing suicide?!
5. Climate was off, it is Summer!, but alas nowhere near warm enough to warrant A/C.
The results are summarised in the following table but for completeness the VCDS log is attached (edited purely for ease of reading).
Tenuous Conclusions.
The dash gauge temperature is accurate in the lower half of its warmup range.
In the upper half it becomes progressively ahead of the "reported" G62 temperatures when warming up, weird.
90℃ occurs 5+ minutes after this value is initially observed on the gauge based on the ECU "feed" of G62.
[FSI dependent - Thereafter the 90℃ is false, part of the dash gauge moderation for driver comfort construct.]
Worth saying even though it not occur here, the gauge comfort moderation keeps the gauge needle on 90℃ except for extreme values.
Andy
The title question enters into many a concern related to coolant temperature and this post is my attempt to use VCDS to try and answer this question, at least for my A2, albeit an FSI but this should not matter too much.
The coolant temperature is "read" by the sensor G62 which has two "outputs", one reports to the engine ECU and the other to the dash [& ultimately the temperature gauge].
The temperature value the ECU "receives" and acts upon is easily observed in VCDS from
The other "output" of G62 to the dash of course can be monitored in a way by simple observation but this is subjective. As an alternative I am led to believe the gauge can also be monitored using VCDS under 'Instruments'.
Good that the coolant temperature on this screen is not labelled G62 as in the Engine controller - argues this is the other "output" of G62, and backed up by the curious value of 30℃ which is different to the Engine screen controller above. 30℃ seems some kind of default for a cold engine in Instruments. The dash ambient temperature was 20℃!
The ideal would be to monitor both "outputs" of G62 side by side with VCDS, ready to compare with gauge readings, but I have yet achieve this but if anybody knows how I am all ears. The best I have achieved is to flit between 'Engine' and 'Instruments' controllers forming a log along the way that contains the coolant temperature "outputs" from each side of G62.
In this context the rest of this post is devoted to the warmup of coolant in my FSI from overnight cold with comparison of my manual observation of the dash temperature gauge. I repeated the exercise 5 times on consecutive days with exactly the same trial, the only change was the ambient temperature that varied by a few degrees. The results were broadly in agreement but not exactly the same, the figures quoted below are a representative.
Some points to note first ...
1. For other A2 models I expect only the range of values will change (& the time to achieve these but no emphasis is placed on time here).
2. The exercise was "driven" by observation of the dash gauge. When I judged the gauge needle was bang on the calibration points of 60, 70,80,90 ℃ the two VCDS temperature values were logged.
3. The VCDS values in (2) are not at the same point in time, it took about 25 seconds to flit between first 'Instruments' and second 'Engine' controllers to log the temperature values
4. As a matter of safety I did not wish to log VCDS values while driving. Not to annoy my neighbours I parked in a nearby quiet country spot with engine idling for some time and this invoked the curiosity of several passing dog walkers - I wondered if they thought I was committing suicide?!
5. Climate was off, it is Summer!, but alas nowhere near warm enough to warrant A/C.
The results are summarised in the following table but for completeness the VCDS log is attached (edited purely for ease of reading).
Coolant Temperature (℃) | Comment | ||
Gauge | Instruments (MVB 17-003.1) | Engine (MVB 01-001.2) | |
59 | 30 | 13 | Just prior to engine start, diverse agreement. Ambient 15.5 ℃ on DIS |
60 | 61 | 62 | Gauge needle begins to move, good agreement |
70 | 70 | 70 | Good agreement |
80 | 76 | 75 | Gauge in advance |
90 | 83 | 82 | Gauge quite in advance |
90 | 94 | 90 | +~ 3 mins. since gauge reached 90℃ |
90 | 105 | 100 | +~7 mins. since gauge reached 90℃. Strong gauge moderation. getting FSI warm! |
Tenuous Conclusions.
The dash gauge temperature is accurate in the lower half of its warmup range.
In the upper half it becomes progressively ahead of the "reported" G62 temperatures when warming up, weird.
90℃ occurs 5+ minutes after this value is initially observed on the gauge based on the ECU "feed" of G62.
[FSI dependent - Thereafter the 90℃ is false, part of the dash gauge moderation for driver comfort construct.]
Worth saying even though it not occur here, the gauge comfort moderation keeps the gauge needle on 90℃ except for extreme values.
Andy
