Background:
The OTC exhaust backpressure kit is a product I originally purchased to conduct testing on my B5 S4.
I came across the kit while organizing my garage. I decided to install it on the GTI to measure the backpressure through the Trackslag catless downpipe and Baun Performance exhaust that are installed on the car.
The gauge is intended to be read with the car stationary and the engine RPM at a high level. This means that the vehicle is not generating boost pressure, and therefore, there is less airflow. This condition didn’t produce enough backpressure to register more than a slight quiver of the needle.
I needed to replace the gauge with a pressure sensor so that I could operate the car on the street at full boost.
Test Results:
After connecting the pressure sensor, I flashed a lower boost tune onto the car that allowed me to log in third gear without experiencing wheelslip.
The OTC line is inserted into the downpipe at the second O2 sensor bung.
I made three pulls to check for consistency, which was achieved, as shown in the chart below.
Examining one pull more closely reveals that the backpressure increases steadily during the pull, as expected, since pressure losses rise with increasing air velocity.
The backpressure peaks at approximately 1.6 psi.