For this measurement I replace the wideband O2 sensor that is positioned prior to the catalytic converter with a pressure sensor.  In this way I am able to measure the exhaust back pressure of most of the exhaust system.

Here is shown a chart containing the manifold  boost pressure and the corresponding backpressure in the exhaust after the turbocharger.

The logical next step after recording the pre-turbo pressure loss with the RS4 intake components on a Stage 3 setup, operating around 24 psi, was to swap the RS4 Y-pipe out and replace it with the S4 Y-pipe.

A comparison of pre-turbocharger pressure loss recorded with these two Y-pipes is shown below:

Expressed as a percentage increase in pressure drop when going from the RS4 to S4 Y-pipe the results look like:

The boost and MAF readings for these two cases is presented in the chart below:

While there clearly is a measurable gain in using the RS4 Y-pipe instead of the S4 Y-pipe it is unclear if the difference would translate into a performance increase for the engine.

I am continuing to record some pre-turbocharger compressor inlet pressure drop as I did with the K03 turbo pressure drop.  Now I am using the TTE550 turbochargers operating with a significantly higher boost pressure.  With this Stage 3 setup I presently have the following boost profile:

Measuring the pressure drop in the turbo inlet pipe produces these results.  Note:  All data not specified as TTE550 is from the BW K03’s.

Not surprisingly the pressure drop is greater with the Stage 3 setup as there is more airflow through the inlet for an equivalent engine speed.

Below is a comparison of the K03 vs TTE550 Boost and MAF readings during these collection sessions.  The greater boost and MAF lines are produced by the TTE550’s.