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.

With having collected enough performance data on the street about the effect of the AWE Exhaust Manifolds on boost onset and pre-turbine back pressure, there was not much left that I was interested in seeing.  Still, with installing exhaust manifolds being a bit of a chore, I decided I would take advantage of having the AWE product installed and dyno my S4.

I was thinking of ways to make the session a bit more productive other than to just gather more data on the AWE manifolds.  I chose to also test the effect that the water-methanol injection system’s nozzle placement has on Intake Air Temperature and the effect, if any, that the Fluidampr harmonic dampener has on torque and power production.

With those three tests planned I arranged for a dyno session at ET Tuning in Union Missouri.  As a precursor to the dyno test procedure, and to get an estimate of the amount of time it would take to swap the harmonic dampener, I swapped my S4 back to the OEM part.

First up was a pull with the car configured as I’ve driven it lately – BorgWarner K04 turbochargers, AWE-Tuning tubular exhaust manifolds, and dual 0.4mm Aquamist WMI nozzles placed in the up-pipes.  One exception was the OEM harmonic dampener being installed, lately I have driven with the Fluidampr, although my last dyno with the BW K04’s was done with the OEM dampener in place.   The tune is unchanged from the last K04 dyno session.

In a post from the day of the dyno I explain the absence of the bumper and headlights.  A comparison of the better pull from the earlier session (red line) with the better of the first two (of several) on this day (blue line) is shown below.

Nothing particularly remarkable stands out.  The torque with the stock S4 manifolds builds more quickly, this could have been expected based on the data that showed the boost building more quickly with the stock exhaust manifolds.  On the dyno the boost profiles are (solid lines stock, dashed lines AWE):

With the AWE-Tuning manifolds the boost is about 200 rpm behind that of the stock exhaust manifolds, although the curves do start slightly later with the AWE manifolds.  The initial boost swing of the stock curves is not a byproduct of the stock exhaust manifolds as I only saw that response on the dyno the day the first logs were recorded.

Tabulating the peak torque and horsepower numbers from all the runs on both days and comparing them, with the stock exhaust manifolds the car made 8 more wheel TQ and 5 less wheel HP than when equipped with the AWE-Tuning exhaust manifolds.

Notably from the datalogs, the AFR during the AWE manifold runs was almost three-quarters of a point richer than the stock manifold runs – potentially altering the power numbers from where they would have been (higher) had the AFR been the same between sessions.

Comparing the Exhaust Gas Temperatures on two pulls that had similar starting conditions:

The rate of temperature increase with both exhaust manifolds is approximately the same.  This is not a surprise since the duration of a dyno pull is relatively short.

This test produced no surprises.  Aftermarket exhaust manifolds predominantly are built to improve airflow, or more correctly reduce pressure losses at high airflow rates, a result of this is a reduction in air speed through the manifold runners as compared to the stock manifolds.  This lower air speed decreases the available energy for spooling up the turbochargers giving the delayed boost onset and slightly reduced low-end torque in favor of better top end horsepower.

In my case, with a small turbocharger and a modest boost profile the effects are minimal, but present.

The next test was to find if the location of the water-methanol system nozzles would affect the intake air temperature.

One of my concerns with the placement of the nozzles in the up-pipes is the potential for a significant amount of the injected fluid to impinge the side walls or opposite side and collect in a stream that does little to help cool the charge air.  This concern had prompted a request for a set of intercoolers with wmi bungs located in the end tanks such that the injection of water-methanol would be almost directly into the oncoming airflow, thus gaining better mixing of the fluid and air.  This placement in the end tanks is shown below.

Several pulls were conducted with the wmi nozzles in the bipipes and the SMIC end tanks.  A compilation of the intake air temperature data is shown below:

There does not seem to be any obvious difference in the temperature profile with change in nozzle placement.

Flow rates were also unaffected:

Note that on pull 2 (F2-V2) on the top chart and pull 5 (F3-V3) on the lower chart that these pulls are after the WMI hose line was swapped and the initial spike in flow rate is on account of the line being filled.

The last test was the most involved labor-wise.  Swapping out the OEM harmonic dampener for the Fluidampr.

Ready to install the Fluidampr:

As it turned out, the Fluidampr pulls proved to be the most involved to decipher.  When comparing the peak numbers of the OEM harmonic dampener versus Fluidampr the swap caused the torque to drop 8 ft-lbs and the power to drop 13 horsepower.

The immediate deduction was the added mass of the Fluidampr is slowing the rotation rate of the crankshaft and diminishing the output.  Knowing how the intake temperatures can affect power production I looked into how the power numbers changed with the smallest recorded IAT of the pull.

The correlation is very strong, so much so that I needed to do more than a simple comparison of peak numbers to deduce what the Fluidampr may have done to engine performance.

In the chart above the green dots are with the OEM harmonic dampener and the red dots are with the Fluidampr.  The orange dot is also with the Fluidampr, but was the first pull after the hour-long break while swapping the parts.

If the number of Fluidampr data points is limited to the pair that have IAT’s similar to that with the OEM part then the difference is only a drop of 3 ft-lbs and 10 horsepower.

Unfortunately one of the two good IAT datapoints happens to be the orange dot, the pull that was first after having the car sitting, and cooling, on the dyno for an hour.  If I take the single reliable datapoint for the Fluidampr, the difference is 1 ft-lb and 4 wheel horsepower, a minuscule difference when comparing values of around 430 ft-lbs wtq and 400 whp.

The dyno chart for this ‘best case’ comparison is shown below with the Fluidamp pull highlighted by the green line.

Results with the Fluidampr are not conclusive, but it does not seem engine power production was increased with the aftermarket harmonic dampener.  This is not all that surprising since the function of the part is not to increase power but help to control harmonic vibrations.