One of the forum members on Audizine contacted me about performing a flow test on a pair of their XS Power side mount intercoolers for the B5 S4.  I was interested to see how this low cost alternative compared to the other side mount intercoolers that I have flow tested so we arranged to have them sent to me for flow testing.

Picture of XS Power SMIC on flow bench
XS Power Driver Side SMIC

Here are a couple of pictures of the XS Power product placed alongside the stock Audi B5 S4 side mount intercoolers and the aftermarket Silly Rabbit Motorsport SMIC’s with RS4 inlet/outlet piping.

(L-R) SRM, Stock, XS Power
Side view of SRM, Stock, XS Power side mount intercooelrs
(L-R) SRM, Stock, XS Power

As I do with all the B5 S4 intercoolers that I have flow tested I took some measurements of the core dimensions.

Picture of XS Power Audi B5 S4 Side Mount Intercooler
XS Power Audi B5 S4 Side Mount Intercooler

The XS Power side mount core measures:

  • 7-11/16″ wide
  • 6-15/16″ tall
  • 3.5″ deep

The core has 10 charge rows, each approximately 7.4 mm wide.  The column containing the fins is 10.7 mm wide.

There are 67 fins in a column, giving approximately 9.7 fins per inch.

One surprising measurement was in the area of the inlet / outlet piping.  The XS Power side mount IC uses an unusually thick pipe, with an inner diameter of 1.65″.


By comparison the stock piping has an ID of 1.81″ – that means that the XS Power inlet pipe has approximately 9-10% less cross sectional area for air to flow into, and out of, the core as compared to a stock S4 intercooler.

With the core measurements taken I brought the XS Power SMIC’s over to the flow bench and tested them out – after doing a bench calibration check.

Picture of XS Power Passenger SMIC on Flow Bench
XS Power Passenger SMIC on Flow Bench

The driver side intercooler flowed 160 cfm @ 28″ of H2O and the passenger side intercooler flowed 168 cfm @ 28″ of H2O.

I was also provided with a data log from the car that contained intake air temperature performance results so that I could plot the XS Power side mounts against the other SMIC’s that I have tested on the flow versus temperature rise scatter plot.  Additionally I had a single data pull from a different car with the same intercoolers.

Three data points is not an overwhelming amount of data upon which to assess a product, but given the magnitude of the temperature rise shown with the two cars it is unlikely that the data I was provided with is significantly different from what would be observed with more samples.  To account for the uncertainty about the variability of the data I chose to use the lowest of the three temperature delta readings that I have.

Combined results are shown below with the other products that have been evaluated.

XS Power intercooler flow test results


The design of the XS Power side mount intercooler does not lend to strong temperature reduction or air flow performance.

  • The XS Power SMIC has the lowest fin density of any core I have measured.
  • The frontal area of the core is less than the stock B5 S4 intercoolers.
  • The core volume is slightly greater (12%) than stock.  By comparison the ‘average’ aftermarket SMIC I have measured has 75% greater core volume than stock.
  • Charge area, the total area for air to pass through the core, is equivalent to the stock SMIC.

Temperature reduction is substantially worse than stock and the airflow is only modestly better than stock.

The only worthwhile benefit I can see the XS Power side mount providing over the OEM S4 intercooler is that the end tanks are metal and welded onto the core and therefore should withstand higher charge air pressure levels without concern.

Audi B5 S4 Information and Testing