MK7 Cooling on Track - Ongoing Analysis
These cars run hot - so lets gather data as to why
I’ve been gathering data logs from not just myself, but from other friends and MANY different people from the MK7 forums. You’ll find below a “report” that I’ve been maintaining for a while now.
All data samples are taken from 200 sec snips of the hottest periods while on track - more specific testing procedures are notated on page 1.
The primary points of interest are the engine coolant temps (ECT) and the intake air temps (IAT) since those are very easily logged pretty much regardless of what interface is used.
Other items being logged are ambient temps, oil temps (when possible - more on that below), boost, vehicle speeds, and average throttle position (TPS). This is due to the variation from driver to driver and track to track which has a FAR greater influence on how “hard” the cooling system is being worked than anything else. TPS was chosen over raw pedal position since the pedal maps can be tuned wildly differently and will vary from tune to tune. TPS is directly applicable from car to car.
Generally speaking, the faster a driver is (on an identical track), the higher the average TPS % will be. Bigger turbo might mean a bit lower average TPS if comparing IS20 vs IS38 on the same track just because less time is spent on the straights. Average speed is logged because it takes more energy to move a car through air at higher speeds than lower speeds, and if you monitor the min/max speeds as well, tracks that have a larger split generally will be harder on the car due to more time spend going from say 40mph up to 130+mph.
It’s worth noting that IAT is to be taken as just a general overview - not absolute (no “OMG this IC drops temps by 2 deg more so it’s better!”). In my opinion the minimum and averages are worth noting as long as they’re not ridiculously out of line from the others. Maximum IATs seen during the data samples are moreso a function of how much time is spent in the corners where the IAT sensor will creep up while off-throttle. You’ll find nearly all the [aftermarket] intercoolers are pretty similar with only a few exceptions in their min and average values.
This entire document is very much still in the data gathering phase, with very basic overviews with a few charts displayed prior to the details of each individual sample. If you open it up in a new page, you can hit “ctrl + f” to find a specific mod or whatever you are curious about. Only the primary drivetrain and cooling parts that will affect temps are notated. Oil temp is a less reliable measure as based on my prior research, there are effectively two oil temperatures within the ECU: “toil” and “toil_srv_intl”. “toil” is the “modeled” oil temperature used in the ECU, and “toil_srv_intl” is the actual raw temperature measured in the oil pan from the sensor. There will be a later article going more in depth but the following points are the important ones:
Dash temperature is accurate.
If you’re logging oil temp and it does NOT match the dash temperature, it is the modeled temp.
The modeled oil temp is wildly inaccurate as soon as you start modifying the car, specifically the cooling system or changing turbos. Generally you can expect a +/-10F deviation if it’s closer to stock. If an oil cooler is added, it may show as much as a 30F difference between the model and dash (actual) values.
For the above reasons, when comparing one sample to another, oil temps must be taken with a grain of salt, paying attention to if it was the ACTUAL or MODELED oil temp being logged. Where possible, I added what the driver saw as peak oil temps on the dash in the case of logging modeled temps.
There will eventually be a deeper dive into analyzing some of these samples as more become available, and especially as recurring sample vehicles make changes and run at the same tracks, or no/minimal changes on different tracks. I’d like to get at least 50 + samples to eventually feed into a model for establishing trend lines where possible.
If YOU want to contribute a log, add the following items to your logging list:
RPM
Boost
Speed
TPS % (not pedal)
Ambient air temp
Intake air temp
Coolant temp
Oil temp (preferably TOil_MDI which matches the dash exactly)
Optional/recommended: Coolant outlet temp - I’ve started collecting this to evaluate how much heat the radiator is rejecting under these scenarios
…then send me an email using the form below. I’ll look it over and possibly ask a few questions, and request you email me your .csv log file(s), at which point I’ll add them to the report.
