Mk7 GTI Stock Intercooler Cruise Temperature

Curious to assess how the GTI stock intercooler performs during a routine drive a VCDS cable was connected to the OBD2 port and temperature readings were taken.

Setup:

The ambient temperature during the drive was 74 degrees F and the drive lasted just over 30 minutes.  For the majority of the drive the car was in motion, there were few stops.  There was a single planned stop where the car sat and idled for 1 minute before resuming the drive.

Mk7 GTI Drive with IAT Logging
Mk7 GTI Drive with IAT Logging

Speed was varied during the drive in accordance with posted speed limit signs and the cruise control was utilized to maintain speed.

Results:

One of the more interesting findings from the test was the continued rise in the Intake Air Temperature throughout the first half of the drive.  Even without stopping the IAT rises to 35 degrees over ambient.

A few times where the vehicle is accelerating relatively rapidly a trend develops wherein the IAT drops dramatically.

Mk7 GTI Stock Intercooler IAT Drop
Mk7 GTI Stock Intercooler IAT Drop

What is a bit peculiar about this trend is that even before the vehicle has returned to cruising speed the IAT has dropped to within about 10 degrees F of ambient, nearly a 25 degF drop in IAT.

Mk7 GTI Intercooler IAT Drop
Mk7 GTI Intercooler IAT Drop

In the two charts above the area of interest is shown with the black vertical lines labeled 1 and 2.

I was expecting to see the temperature drop lag slightly as the vehicle speed increases, and I was not expecting to see such a substantial drop in IAT.

Adding engine speed to the chart helps to explain the rapid drop in IAT.

Mk7 GTI Intercooler IAT Drop with Engine Speed
Mk7 GTI Intercooler IAT Drop with Engine Speed

Even though the IAT is dropping rapidly before the vehicle reaches the steady state cruise speed, the engine speed has increased significantly, which correlates with an increase in airflow through the intake system.  The increase in airflow results in less heat transfer from the intake pipes to the air, and thus giving a lower temperature reading when that air reaches the intake air temperature sensor.

The speed changes from low to higher speed were done at partial throttle and may not have triggered the turbocharger to generate positive boost pressure (boost pressure was not logged).  Had boost pressure been created it is likely that the temperature changes would be different as a result of the compression of the intake air.  Compressing the air would have raised the temperature.

Conclusion:

The Mk7 GTI stock intercooler does not perform all that well under steady state conditions.

The point of having the intercooler on the vehicle is to cool the compressed charge air being discharged from the turbocharger compressor and that aspect of the stock GTI intercooler performance was not evaluated during this drive.

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