Table of Contents
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.
| Brand | Cost | Description |
|---|---|---|
| CTS Turbo Catless | $449 + $199 Cat. | 3.5″ to 3″ piping |
| ARM Motorsports Catted | $447 | 200 Cell High-Flow Catalyst TIG welded T304 grade stainless steel 3″ piping |
| Trackslag Catted | $1130 | EU5 oversized 200 cell catalyst 304 stainless steel / Tig welds back purged 4″ to 3″ piping |
| BCS Powervalve | $1092 | 125 mm oversized 100 cell cat 304-grade stainless steel 3″ piping |
| Integrated Engineering | $800 | 200 cell catalytic converter / metal matrix “Our catalyst is also a very large diameter,” 304 stainless 3″ piping |
| AWE Tuning | $1,745 | 200 cell HD high-flow catalyst. T304 stainless steel 3″ piping * DISCONTINUED * |
| 034Motorsport | $845 | 101.6mm Euro 3 Racing Catalytic Converter – 200 CPI 304 Stainless Steel 3″ piping |
| MAPerformance | $1150 | 304 stainless steel 3″ piping |
| Unitronic | $ | 400-cell 5″ GESi cat 304 stainless steel 3″ piping |
| APR | * DISCONTINUED * | |
| Milltek | $1276 | 200 CPI catalytic converter 304 stainless steel 3″ tubing |
| HPA | $1000 | 300 cell metal cat 304 stainless steel 3″ piping |
| AMS | Only available for Golf R | |
| USP Motorsports | $600 | 200 cell Metal Catalyst Stainless steel 3″ piping |
| Baun Performance | 4″ GESi cat 3.5″ piping | |
| 485 Design | 4″ GESi cat 3.5″ piping | |
| CCDesignFab | 4″ 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
- Stock GTI downpipe
- USP downpipe
- CTS Turbo downpipe
- Trackslag downpipe
- ARM Motorsport catted downpipe
- ARM Motorsoprt catless downpipe
- CTS vs ARM boost onset
- ARM (catted) vs Trackslag boost onset
- ARM (catted) vs Trackslag acceleration
- ARM Catless vs ARM Catted vs Trackslag Catted Boost Onset
- Trackslag (catted) vs ARM (catless) Power Estimates
- ARM (Catted) vs ARM (Catless) Power Estimates
- Baun Performance GESI 4″ downpipe flow test
- Trackslag (Catless) flow test
6.2.2. Test result summary
