This report was originally published on Audiworld in October of 2006.

Stage I – Bench Test

Objective – Determine how the RS4 intercooler responds to heating and cooling under conditions similar to what the stock and IPP intercoolers were tested under.

Procedure – The same as for the stock and IPP intercoolers.

Configuration – The same as for the stock and IPP IC test.

Constraints – The same as for the stock and IPP IC test.

Results – The chart below shows the results for all three intercoolers. The RS4 intercoolers rose in temperature at the same rate as the IPP intercoolers, less than the stock IC’s, but reached a steady state temperature 10 degrees Fahrenheit higher than the IPP intercoolers. Once the fan was turned on the RS4 intercoolers cooled more rapidly than the stock or IPP intercoolers. The steady state cool temperature of the RS4 IC’s was 1 degree warmer than the IPP intercoolers.

The next chart shows the rate of cooling once the fan was turned on and the intercooler began to cool down. Over the first 30 second measurement interval the RS4 IC’s cooled most rapidly; the IPP IC’s cooled the slowest. (Note that the stock intercoolers did not begin to cool immediately, as the IPP and RS4 IC’s did.)

Over the next 30 second measurement interval the trend remained the same. By 90 seconds all three IC’s were cooling at an equivalent rate.

The affect of the different rates of cooling shows up on the first chart. Both the RS4 and IPP intercooler begin to show a bottoming out in the rate of cooling around 120F. Both IC’s are close to their steady state temperature at this point.   In cooling to 120F the RS4 intercooler drops 75F in 120 seconds. The IPP intercooler drops 65F in 150 seconds. By more rapidly cooling, the RS4 IC’s produces a greater total temperature drop over shorter period of time as compared to the IPP intercoolers.

Stage II – Road Tests

Objective – Determine how the RS4 intercoolers respond to heating and cooling when mounted on the S4 under conditions similar to what the stock and IPP intercoolers were tested under.

Procedures – The same as for the stock and IPP intercoolers.

Configurations – The same as for the stock and IPP IC test.

Constraints – The same as for the stock and IPP IC test.

Results –

1) Cruise Test

With the outside air temperature between that recorded during the stock and IPP tests, there was a noticeable decrease in the Intake Air Temperature with the RS4 intercoolers installed at similar driving speeds. The difference was generally between 5-10F less than the stock and IPP IC’s had shown.

2) Speed Test

In fourth gear at 3000 rpm the RS4 intercoolers reached a steady state temperature approximately 5F cooler than the stock IC’s with no indication that the temperature would have risen if the test was run further in that gear.

In third gear at 3000 rpm the RS4 intercoolers increased in temperature approximately 4F over the previous steady state temperature. The temperature difference between the RS4 and stock IC’s increased slightly, with an additional temperature difference occurring between the IPP and RS4 IC’s.

When changing to second gear and decreasing the vehicle speed to 27 mph the temperature of the intake air began to rise steadily. After rising approximately 10F it began to steady out. Shortly thereafter the car was forced to slow and turn around, which caused a slight additional increase in temperature.

At this slowest speed the RS4 IC performance was very similar to the stock IC. The IPP IC was 10F warmer when the data collection was halted.

3) FATS Test

During the FATS tests the temperature of the RS4 IC’s followed a similar trend as the stock and IPP IC’s. There were some differences noticed, the RS4 IC’s reached a cooler temperature in the middle rpm region. This affected the FATS IAT Rise plot.

Upon first look it’s clear that the RS4 IC’s raised in temperature a greater amount than the stock or IPP IC’s. What becomes clear is that the lower temperature drop in the middle rpm is driving this result because the starting and ending temperatures are nearly the same between all of the intercoolers.

The post-FATS cool down shows some difference between the RS4 IC and the other two systems. Despite slowing the vehicle more rapidly during this series of tests and to a lower speed, the RS4 intercoolers showed the most rapid temperature recovery of the three.

The chart of post-FATS temperature drop shows the RS4 IC’s tying with the second IPP test for most temperature drop.

It important to consider that only three FATS tests were performed with the RS4 IC’s, limiting the amount of confidence that can be given to the results. As a whole the data collected is representative of the RS4 intercoolers, but in order to make more confident conclusions about their performance versus the other IC’s on the FATS tests, additional runs would be needed.

Final Conclusions –

The RS4 IC’s showed the most rapid temperature drop on the bench test. They were the top performer on the cruise and speed test; on the FATS test their performance was close enough to the performance of the other IC’s to make a clear-cut winner on that test uncertain.