Mk7 GTI Downpipe Testing

1.0 Background

1.1 Summary

This project is being undertaken to continue evaluating aftermarket performance products available for the Mk7 GTI. For this evaluation the exhaust downpipe is the test subject. The downpipe receives exhaust gasses from the turbocharger turbine housing and directs them to the rear exhaust pipe. The location of the downpipe results in the part affecting the turbine expansion ratio which affects turbocharger and engine operating efficiency. This project will seek to quantify and compare any performance changes produced by different vendor downpipes.

1.2 Previous Test Results

The stock Mk7 GTI downpipe was previously compared to an aftermarket downpipe equipped with a catalytic converter in a flow test conducted using a flow bench. The aftermarket downpipe was found to flow more than the stock GTI downpipe. This comparison is documented here.

2.0 Purpose of Test

Determine if downpipes affect the performance of the Mk7 GTI turbocharger and engine. Test a sampling of aftermarket downpipes available for the Mk7 to determine which provides the greatest performance gains.

3.0 Systems under test

3.1 Downpipe

The downpipe section of the exhaust system will be the product evaluated during this testing.

3.2 Test items

As of July 12, 2021 the following table lists potential products to be tested. Not all of these will be tested.

CTS Turbo Catless$449 + $199 Cat.3.5″ to 3″ piping
ARM Motorsports Catted$447200 Cell High-Flow Catalyst
TIG welded T304 grade stainless steel
3″ piping
Trackslag Catted$1130EU5 oversized 200 cell catalyst
304 stainless steel / Tig welds back purged
4″ to 3″ piping
BCS Powervalve$1092125 mm oversized 100 cell cat
304-grade stainless steel
3″ piping
Integrated Engineering$800200 cell catalytic converter / metal matrix
“Our catalyst is also a very large diameter,”
304 stainless
3″ piping
AWE Tuning$1,745200 cell HD high-flow catalyst.
T304 stainless steel
3″ piping
034Motorsport$845101.6mm Euro 3 Racing Catalytic Converter – 200 CPI
304 Stainless Steel 
3″ piping
MAPerformance$1150304 stainless steel
3″ piping
Unitronic$400-cell 5″ GESi cat
304 stainless steel
3″ piping
Milltek$1276200 CPI catalytic converter
304 stainless steel
3″ tubing
HPA$1000300 cell metal cat
304 stainless steel
3″ piping
AMSOnly available for Golf R
USP Motorsports$600200 cell Metal Catalyst
Stainless steel
3″ piping
Baun Performance4″ GESi cat
3.5″ piping
485 Design4″ GESi cat
3.5″ piping
CCDesignFab4″ GESi cat
4″ or 3.5″ piping
Ultimate Racing

3.3 Test instrumentation

Airflow measurements will be made using a PTS flowbench and digital manometer.

4.0 Scope of downpipe test

4.1 Test environment

Testing will be conducted first using a flow bench to isolate the downpipe from other system components.

Products that show positive results during flow testing will be installed on a Mk7 GTI for further evaluation under street driving scenarios.

The remainder of the plan for this test MIGHT be completed later.

4.2 Test and test conditions

4.3 Test criteria

4.3.1 Assessment standards

4.3.2 Completion standards

4.4 Limitations to scope

5.0 Method of downpipe test

5.1 Test method and procedures

5.2 Support requirements

6.0 Project management

6.1 Supplies

6.2 Reports

6.2.1 Product test results

6.2.2. Test result summary

Trackslag Catless Downpipe Flow Test

7.0 References