ATTENTION: This site has been created as a public webpage where I can post information about my Audi S4. You will find links to various topics about this automobile. All opinions and statements are purely my own and should not be taken to be anything authoritative or definitive. Follow this link to read my philosophy on modifications.
Copyright 2003-2005.

 

 

 

 

 

 

 

 

 

 

 

 

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DYNO TESTING
Reason:

Evaluate the performance of my S4 in "near stock" condition and collect data to try to evaluate how well the car is running during. My goal was to assess the car's performance in a near stock configuration prior to the installation of the APR Stage III kit so that I would be able to assess the performance gains of the Stage III kit and determine how well the car was running after the modifications were made.

Test Setup:

I wanted the car to be as close to stock as I could get, in order to have a useful comparison to the dynoplot that APR provides for their base S4 and their S4 with the APR Stage III kit. My car was set up with the stock Audi ECU, AWE downpipes, Supersprint exhaust, and stock Audi intercoolers. Reinstalling the stock downpipes and exhaust on the car was not feasible given the cost and time constraints I was operating under. As well, those parts are not included in the Stage III kit. I tried to schedule the stock dyno pulls as close to the installation of the kit as I could, so that the weather conditions would not change too much between the baseline test and the test once the kit was installed.

I unfortunately had about an hours drive to get to the shop where the dyno testing was to take place, which meant the engine compartment and intercoolers were well heated for the testing. The shop temperature and humidity for the testing were 62 degrees and 27%.

In addition to the data collected from the Dynojet I also hooked up a Vag-Com to the car to record intake air temperature, timing, and boost.

Results:

The three third gear pulls are shown on the graphs below.


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The first graph is the basic hp/torque plot versus rpm with the addition of intake air temperature. A couple interesting things to point out. First, you can see how poorly the cooling fan at the shop performs. Despite being a large fan, it is not nearly as effective at cooling the intercoolers as when the vehicle is moving on a road. With the car just sitting and idling with the fan blowing onto the front of the car the intake air temperature is around 100 deg F, roughly 40 degrees higher than ambient. I've generally found that when driving the car on the road at a stable speed the intake air temperature will be approximately 10 degrees higher than ambient.

The second interesting observation is that despite the intercoolers becoming heat soaked and intake air temperature increasing dramatically on the second and third runs, between 15-25 degrees at the beginning of the runs, and 40 degrees hotter on the third run. When the car is producing peak hp, around 5500 rpm, the difference in peak hp numbers between the best and worst runs is 1.5 whp.


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The next graph again shows hp/torque, adding lines for ignition timing (the dashed lines), and requested (solid line) and actual (dashed line) boost. An interesting relationship can be seen; as the intercoolers get hotter, reflected in the increasing intake air temperature at the beginning of each test, intake air temperatures for each run rise (air becoming less dense). The boost levels rise accordingly (to compensate for the less dense air entering the engine), and the timing is pulled back (lessening the possibility of pre-ignition as the air temperature in the cylinder rises).


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The last graph shows the hp/torque curves, with the air-to-fuel ratio overlaid.