In addition to the White Dog Racing Bipipes that I flow tested a couple of days ago the box contained a set of the intercooler inlet pipes that replace the stock components for use with the Silly Rabbit Motorsport RS4 side mount intercoolers.

These inlets in addition to being made of metal are larger in diameter than the stock components they replace.

For the flow testing I attached the inlet to the SRM intercoolers and mounted them onto the flowbench.  I began with the stock hardpipes and couplers supplied with the SRM intercoolers.

Both the driver and passenger side flow performance was measured.

Then I swapped to the White Dog Racing inlet pipes and checked the airflow again.

 

Finally, for comparison with a completely stock setup I used the stock S4 intercoolers with the stock inlets.

Results:

Airflow through each of the setups was measured at a depression of 28″ of H2O.

The chart above illustrates a number of pieces of data:

1. The red bar and purple bar are the airflow readings from a stock intercooler and the SRM RS4 intercooler – without any inlet piping attached.  It is clear that in this configuration the SRM RS4 IC greatly outflows the stock intercooler.
2. The green bar shows the reduction in airflow through the stock intercooler when the stock inlet piping is attached.  There is a modest decrease in airflow as compared to the IC alone.
3. The orange and blue pair of lines are showing driver versus passenger side results of swapping inlet pipes between stock and WDR.  The passenger side has a higher airflow for each pipe arrangement.  Their is a small improvement in airflow when switching from the stock to WDR parts. (It should be pointed out that readings taken under operating conditions would be different as charge air under boost is denser and thus develops more back pressure).
4. Finally, the SRM RS4 intercooler undergoes a substantial drop in airflow with the addition of the inlet piping, regardless of whether it is stock piping or the WDR piping.

Conclusion:

The airflow through the intercooler and inlet is increased measurably, but only slightly, by using the larger White Dog Racing hard pipes, when evaluated on the flow bench.

For a typical user the larger inlet pipes may not provide much performance benefit, but for the all-out build where optimizing every part matters, the White Dog Racing hard pipes do provide measurable gains.