An XS-Power bipipe was delivered a few days ago to go into the Get Healthy Silver S4 that I’m currently working on.   Since the product has not been flow tested, and this one is available, I decided to stick it onto the flowbench and see how it performs.

The XS-Power bipipe intake diameter is 51 mm on the inside of the pipe.  Here is how this compares to the other alternative bipipes I have measured the inlet size of:

• APR:  49.8 mm
• WDR-54:  52.4 mm
• WDR-60:  59.3 mm
• RS4:  61.1 mm

I tested the XS-Power Bipipe with a Stock B5 S4 Throttle Body at 28″ of H2O and recorded a CFM of 545.  This compares to some of the other bipipe options as follows:

Peak airflow ranking correlates with the inlet diameter, the XS-Power bipipe places just above the APR bipipe and a little below the WDR-54 bipipe.

With the APR bipipe being discontinued the XS-Power bipipe presents a new option that is similar in design as well as performance.

In the past I’ve noted that different results occur when the inlet hoses are connected to the bipipes.  The comparison above is using just the bipipe without an inlet hose.

To illustrate how the inlet hose alters the airflow through the bipipe a comparison with and without the inlet coupler hose is shown below:

The APR bipipe shows the greatest increase in airflow with the coupler hoses attached, having a maximum airflow equivalent to the XS-Power bipipe within the measurement margin of error.  All of the bipipes see a reasonable gain in airflow when the Intercooler coupler hose is attached to the end of the bipipe.

A Subaru owner contacted me about putting their airbox on the flowbench to determine how closely the Subaru table for MAF voltages matched with real airflow.

I ran this experiment with the S4 MAF Sensor and did not get a very good match so I was interested to see how things would turn out with the Subaru setup.

Because the voltage from the MAF sensor is not read by the hardware for measuring the flow bench airflow and pressure drop I needed to hook up a multimeter to the MAF sensor 5V output wire and take manual readings at various airflows.  Although this method is not a precise as it would be if all sensor values were read by the same datalogger, the results were good.

Agreement between the Subaru MAF table values and the measurements taken on the flow bench were good.

As a follow-on to the initial flow testing performed with the White Dog Racing Front Mount Intercooler I wondered what the airflow through each half of the FMIC would be.

I attached the WDR FMIC to the flow bench again, this time using a thick piece of plastic to cover one of the inlets and then sliding the coupler hose over the plastic to hold it in place and form a seal.

Then with just a single inlet open I tested the intercooler again.

I was a bit surprised by the difference in airflow readings between the two halves.  The passenger side is flowing approximately 14% more than the driver’s side.

Each half of the core has the same number of charge rows, 17.

Based on the physical appearance of the cores the only immediately obvious difference that I would guess to be causing the difference is the longer exit path that the air from the driver’s side flows through on the top side of the cores prior to exiting the FMIC.