Background:
The Trackslag 4″ downpipe for the Mk7 GTI in the 200 cell per inch catted form was previously flow tested. For this test, a catless version of the Trackslag 4″ downpipe is the system under test.
Test Procedure:
The flow bench is first checked with a calibration plate to ensure the measurements are accurate.
Next, the downpipe is attached to the flowbench using a 3″ straight silicone coupler and a 3″ adapter with an expanding outlet. At the inlet of the downpipe a bellmouth is attached to help smooth the air entry into the downpipe.
The flow bench is operated at a depression of 16″ of H2O and air is drawn in through the downpipe inlet and into the flow bench.
Trackslag Test Results:
The Trackslag 4″ catless downpipe flows 573 CFM @ 16″ of H2O.
This result along with other downpipes that have been tested are shown on the chart:
Conclusions:
The Trackslag 4″ downpipe for the Mk7 GTI without a catalytic converter was flow tested using a PTS flow bench. The catless Trackslag downpipe flowed 573 CFM @ 16″ of H2O.
This result is a surprising 10% increase over two other catless downpipes that have been tested (~240% over the stock GTI downpipe). The reason for the surprise with this outcome is that all of the downpipes are predominantly 3″ in diameter with the differences in diameter occurring primarily toward the inlets. Presumably, the Trackslag downpipe incorporates other design elements that contribute to reducing drag significantly compared to the other catless downpipes that were previously tested.
To verify the results were correct, the test with the Trackslag was repeated later, producing the same 573 CFM @ 16″ as during the first test.