Mk7 GTI Radiator External Fin Flow Test


Some questions about the interaction between airflow from the stock location intercooler and radiator coincided with work I am doing to swap the turbocharger and intercooler on my GTI.

Turbocharger & IC Swap
Turbocharger & IC Swap

With easy access to the radiator, I decided to make a detour and flow test the external fins of the stock GTI radiator.

Radiator Flow Test Prep
Radiator Flow Test Prep

Looking at the fins, they are shorter and more closely spaced than the stock GTI intercooler.

Radiator Fin Close-Up
Radiator Fin Close-Up

Test Process:

The airflow through the external fins will be measured using a flow bench with an adapter that draws air through a subsection of the core.

The airflow will be measured three times to calculate an average flow rate while rotating the core between measurements to minimize the influence of the core orientation.

First, the flow bench calibration is checked using a calibration plate and then the adapter is attached to the bench.

Radiator Flow Test Calibration Check
Radiator Flow Test Calibration Check

The radiator is set down on the adapter and airflow through the external fins is measured at a depression of 10″ of H2O.

Radiator External Fin Flow Test
Radiator External Fin Flow Test

Test Results:

The airflow rate measurements are:

  1. 383 CFM @ 10″ of H2O
  2. 384 CFM @ 10″ of H2O
  3. 383 CFM @ 10″ of H2O

Average: 383 CFM @ 10″ of H2O.

The chart below shows the external airflow rate for a collection of intercoolers available for use with the Mk7 GTI.

CTS FMIC External Air Flow Test
External Air Flow Test

The chart is current as of the day of the post.


The Mk7 GTI stock radiator was flow tested to determine the airflow rate through the external fins and to compare the measurements with intercoolers that are available for use on the Mk7 GTI.

The flow rate through the stock GTI radiator is 383 CFM @ 10″ of H2O.


6 thoughts on “Mk7 GTI Radiator External Fin Flow Test”

  1. Interesting read. I wonder how it would fare with the ac condenser and intercooler in front of it. Sort of mimicking having the whole stack on the car.

    1. I don’t think this test would produce good results trying to do that because of the adapter drawing air in through a portion of the core it’s in contact with. Air would be drawn through the IC and condenser, and spaces between them, differently than through the radiator.

  2. Tony Mester

    Interesting data point for frame of reference vs the available intercoolers. Next up: condenser?

    1. I don’t have a spare on hand and removal isn’t a realistic option.

  3. Very interesting read. I wanted to know if you have ever done tests on cooling the air that passes the turbo, meaning the intercooler or as in ea288 tdi engines the “charge air cooler. I dont know if the ea888 engines have an intercooler or water-to-air cooler. if the case is latter, i want to learn if we can make it more efficent at cooling the air. in the “self study program” supplied by VW the charge air cooler liquid cycle is called low-temprature cycle. Can we or should we change this liquid as a maintenance requirement?

    1. The Mk7 GTI uses an air-to-air intercooler.
      I don’t know what maintenance would be performed on a water-to-air system, changing the water occasionally seems plausible.

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