ARM Downpipe Flow Test

ARM Motorsport Cat-less DP Flow Test


ARM Motorsport provided a sample of their cat-less downpipe to conduct a flow test as a follow-up to the flow test with their catted Mk7 downpipe.

Previously a CTS Turbo 3.5″ cat-less downpipe was flow tested and I am interested to learn how the 3″ ARM cat-less downpipe compares.

Test Procedure:

First, the flow bench is checked for accuracy using a calibration plate.

Next, the downpipe is attached to the flow bench using a silicone coupler that is the same 3″ diameter as the piping at the outlet end of the downpipe.

A bell-mouth is attached at the inlet to smooth airflow into the downpipe.

ARM DP Flow Test - Bell Mouth Inlet
ARM DP Flow Test – Bell Mouth Inlet

The flow bench is operated at a depression of 16″ of H2O and the airflow measured at that depression is recorded.

Test Results:

The ARM Motorsport cat-less downpipe flows 520 CFM at 16″ of H2O.

ARM Downpipe Flow Test
ARM Downpipe Flow Test

This result is compared with the stock GTI downpipe, which has two catalytic converters, and the CTS 3.5″ cat-less downpipe, below:

ARM Catless DP Flow Test
ARM Cat-less DP Flow Test

The airflow measurements from a few other downpipes that were tested in this manner are shown below:

Mk7 ARM Catless DP Flow Test Summary
ARM Cat-less DP Flow Test Summary


The ARM cat-less downpipe flows 520 CFM @ 16″ of H2O.

This is roughly a 200% increase over the stock GTI downpipe. Compared to the ARM Motorsport catted downpipe the cat-less model increases airflow by approximately 35%.

Comparing the 3″ ARM downpipe to the CTS cat-less downpipe that has a 3.5″ inlet there is no significant difference in airflow at the test depression.


ARM Motorsport Mk7 Downpipe

4 thoughts on “ARM Motorsport Cat-less DP Flow Test”

  1. Any plans to test one of the GESI catted Baun performance downpipes by chance?

  2. Will you test with APR downpipe sometime soon? I heard it’s one of the loudest but idk about airflow

    1. If I can easily get access to one I will. Most parts that I get access to for testing have been from purchasing them, so I have to weigh the costs and benefits.

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