Mk7 GTI FMIC Comparison Test

1.0 Background

1.1 Summary

This project continues an evaluation of intercoolers available for the Mk7 GTI.

Front-mounted intercoolers (FMIC) which are located in front of the air conditioner condenser are the system under test. Intercoolers that work in parallel with a stock location intercooler, referred to as a bicooler, are included in the scope of this test.

Treadstone TR8C FMIC Installation
Front Mount Intercooler

Two objectives of this test project are to increase the number of FMIC products with direct peer comparisons and expand the test conditions beyond those previously used.

1.2 Previous test results

All intercoolers in this effort have been part of previous flow testing. Some of the intercoolers have been previously tested on the street, but at the time of that testing, the GTI was equipped with an IS38 turbocharger whereas for this comparison the GTI will be equipped with an IHI IS20 turbocharger.

2.0 Purpose of test

Comparison – Objectively evaluate the vehicle and engine performance when changing between the available systems under similar operating conditions.

3.0 Systems under test

3.1 Intercooler

The Mk7 GTI is equipped from the factory with an air-to-air intercooler. This stock intercooler is located in front of the radiator and behind the air conditioning condenser. An alternative to the stock location intercooler is a variety of aftermarket front-mounted intercoolers (FMIC) that are located below the front bumper crash bar and in front of the air conditioning condenser.

A third option is a bicooler, which combines the front-mounted intercooler with the stock location intercooler using a pair of branched silicone hoses.

Both front-mounted and bicooler alternatives are the subject of this test series.

3.2 Test Item Table

As of April 2024, the following table lists the candidate front-mounted intercoolers for this test.

ARM Motorsports$54722″ x 9″ x 3.25″ – Bar & PlateAcquired
Baun Performance$90022″ x 9.25″ x 3.25″ – Bar & PlateAcquired
CTS Turbo$45024″ x 8″ x 2.75″ – Bar & PlateAcquired
ECS Tuning$55026” x 7 ⅞” x 3.0” – Bar & PlateAcquired
JD Eurosport$80024″ x 7.8″ x 3.5″ – Bar & PlateSkip
Neuspeed$85026″x 6.5″x 3″ – Bar & PlateAcquired
Treadstone TR8C$27222″ x 7.8″ x 3.5″ – Bar & PlateAcquired
Forge Motorsport$882BicoolerAcquired
FMIC Products

Mk7 Front Mount Intercoolers
Mk7 Front Mount Intercoolers

3.3 Mk7 GTI

The intercoolers will be installed on a Mk7 GTI operating with an IHI IS20 Turbocharger and an aftermarket customized Stage 2 tune from Stratified Automotive Controls. The boost curve for this tune is shown below.

Stratified Custom IS20 Tune

3.4 Test Instrumentation

Temperature measurements will be made using the vehicle’s built-in sensors and supplemental Resistance Temperature Detectors (RTD). 

Pressure measurements will be made using the vehicle’s built-in sensors and a supplemental 4 Bar MAP sensor.

Data will be recorded using a DATAQ DI-149 high-speed data logger and a Cobb Accessport.

Vehicle acceleration data will be recorded using a Racebox logger.

4.0 Scope of Intercooler Test

4.1Test Environment

Temperature readings will be made while the vehicle is operating on the street. The GTI will not be tested on a Dynamometer which would result in the vehicle being stationary and susceptible to unrealistic airflow through the intercooler.

4.2 Test and Test Conditions

  • Third gear acceleration – Full-throttle acceleration in third gear up to a minimum engine speed of 6300 RPM.
  • Sequential loading – Repeated acceleration and deceleration cycles across a speed range including 47 mph to 84 mph for a minimum of 9 pulls.

4.3 Test Criteria

4.3.1 Assessment Standards

Success / Failure criteria – Products will be evaluated for performance differences relative to other products. There are no predetermined threshold or objective values against which the products will be evaluated.

An AMS stock location aftermarket intercooler paired with a Neuspeed Golf R FMIC as a bicooler pair will be recorded to provide comparison data.

AMS Performance Mk7 GTI Intercooler
AMS Performance Mk7 GTI Intercooler
Neuspeed Mk7 FMIC
Neuspeed Mk7 FMIC

A stock Mk7 GTI intercooler will be recorded to provide comparison data.

Stock GTI IC and adapter sleeve
Stock Mk7 GTI IC

4.3.2 Completion Standards

Testing will end when sufficient cooling and airflow data is recorded to support a comparison of the measures of interest for the test articles.

4.4 Limitations to Scope

There are a number of operating conditions that an intercooler could be subjected to that will not be evaluated during this test. Some examples are 0 to 60 mph acceleration, 60-130 mph full-throttle acceleration, autocross, drag strip, and road course driving.

There are several aftermarket intercooler cores available that could be built into a custom intercooler product. There are no plans to have a custom-built intercooler be part of this test.

There are aftermarket FMIC options for the Mk7 that require extensive modification to the front crash bar to fit on the GTI. These products are not part of the test.

The hoses that most of these intercoolers use to join with the charge pipes are sized to work with the stock charge pipes. There is no provision in the stock throttle body charge pipe to install a temperature probe. The intake air temperature (IAT) inside the intake manifold only provides accurate readings when there is a high airflow rate through the intake manifold. This will limit useful measurements to conditions of high airflow.

The intercooler efficiency is calculated by measuring the air temperature leaving the turbocharger and subtracting the intake air temperature. This value is compared with the turbocharger outlet air temperature after subtracting the ambient air temperature. The temperature measurement at the turbocharger compressor outlet will be higher than the temperature of the air entering the intercooler due to the cooling of the air as it passes through the hot side charge air pipe. This will cause the calculated efficiency to be higher than if the measurement was made at the intercooler inlet. Since all intercoolers will be measured at the same location, the relative standings will not be affected.

5.0 Method of Intercooler Test

5.1 Test Methods and Procedures

Full-throttle third-gear acceleration from 2000-6500 RPM

The GTI is operated with the DSG transmission in manual mode and third gear. When the engine RPM is around 2000 the accelerator pedal is fully depressed and the car is continuously accelerated to an engine RPM of 6500. The car is then slowed and the transmission returned to automatic mode.

The car is driven for a short time before repeating the process in sequence nine more times. An example recording session is shown below:

Data Collection Overview

The acceleration time from 47 mph to 84 mph is measured by the Racebox and/or Dragy.

Street Data Collection
Racebox Data Collection

5.2 Key Contributing Factors

FactorsTypeActionRangeEase of ControlData TypeComment
Ambient air temperatureConstantHold78-85FModerateContinuousPrimary concern for response.
Boost pressureConstantHold0-28 psiEasyContinuousVaries but with repeatability
Starting IATCovariateRecord~80-120FHardContinuousIAT sensor inaccuracy
Time under loadConstantHold4-5 secondsModerateContinuous
Fuel QuantityNoiseIgnore33-100%EasyContinuousFactors in vehicle weight that affects acceleration rate
Recovery interval timeCovariateRecord10-200 secondsHardContinuousIAT sensor inaccuracy
Recovery interval avg. speedNoiseIgnore30-50 mphModerateContinuousIAT sensor inaccuracy
IntercoolerControlVary1 thru 10EasyNominal

Note: In the above table, Control factors are purposely varied. Covariate factors are allowed to take on values without intervention but are recorded. Constant factors are held fixed at a particular level. Noise factors are essentially ignored.

5.3 Key Response Variables

ResponseDescriptionUnit of Measure
IATIntake Air Temperature measured inside the intake manifold – KPPDegrees Fahrenheit
Pressure DropThe pressure difference between the turbocharger compressor outlet and intake manifoldPounds per square inch
Delta TDifference between the Intake Air Temperature and Outside Air TemperatureDegrees Fahrenheit
T-OutAir temperature at the turbocharger compressor outletDegrees Fahrenheit
EfficiencyIntercooler efficiency. Turbo compressor discharge air temperature versus outside air temperature (OAT) compared with intake air temperature versus OATPercent
Acceleration TimeTime to accelerate vehicle from 47 mph to 84 mphSeconds
Peak WHPCalculated from the vehicle acceleration data using Virtual Dyno.Horsepower

6.0 Project Management

6.1 Supplies

Products available for testing are identified in section 3.2 Test Item.

6.2 Reports

6.2.1 Product test results

The following links are to pages dedicated to presenting the detailed results for each intercooler.

  • Stock Mk7 GTI – Baseline
  • AMS / Neuspeed – Baseline

6.2.2. Test result summary

The following charts show summary comparisons of the key performance parameters.

7.0 References