Stock Turboback

Flow testing the full B5 S4 turboback exhaust system and comparing to the results of testing the Autospeed downpipes and 034 Motorsports 3.5″ single (3″ mid-pipes with dual Magnaflow mufflers) exhaust system.

The setup:

The chrome exhaust tips on the stock exhaust are not airtight, so I needed to tape them up and then wrapped the tape in a rubberized band.

Audi B5 S4 stock turboback exhaust

The results:

Stock turboback exhaust pressure drop

B5 S4 stock turboback exhaust flow


A well optimized aftermarket exhaust system can substantially outperform the B5 S4’s stock turboback exhaust system.


The following chart shows the performance of the stock muffler without downpipes.

Audi B5 S4 muffler airflow

Audi B5 S4 Information and Testing