Testing on the six cars took a total of seven hours. By now we know you just want to see the numbers, so enough background and on to the results.

For peak torque and horsepower, APR nosed ahead of the field and put out a pack-leading 303.1 lb-ft of torque and 302.1 horsepower. Generally speaking the rest of the field was tightly bunched right behind APR (within 10 lb-ft and 4.9 hp of the APR-leading numbers) but there has to be a winner, right?

The big surprise of the day was the AMD car coming in a distant 6th place, behind even the supposedly baseline-providing stock S4. The AMD tuned vehicle made a whopping 31.7 lb-ft torque less and 2.8 hp less than stock - Confusing and hard to explain results considering the upgrades to the car.

Peak Torque (lb-ft) Peak WHP
APR 303.1 APR 302.1
OCT (res) 301.3 OCT (res) 298.3
OCT (non-res) 297.9 OCT (non-res) 301.6
GIAC 293.7 GIAC 297.2
Stock 277.7 Stock 278.8
AMD 246.0 AMD 276.0

  • APR had the highest peak power
  • APR had the highest peak torque
  • OCT had the most consistent power curve (other than stock)
  • OCT had the most overall torque
  • APR had the most overall WHP

Dyno Graphs




OCT Non-resonated

OCT Resonated





OCT was the only software that did not lose torque compared to stock over the RPM range. While the APR car had a peak torque higher than any other car, it was under the stock torque curve between 4000-4700 rpm. The GIAC car had a huge deficit in torque between 3000-5000 rpm compared to stock; even though it's peak torque was at 3000 rpm it could not hold the power across the 3000-5000 rpm range. AMD was way below stock torque output during the entire rev band. Both OCT cars stayed well above the stock torque curve, and did so consistently.

OCT was also the only software that didn't lose HP over stock. While APR had the highest peak WHP, it had less HP than stock between 4000-4500 rpm. GIAC had a significant loss of HP relative to stock during the same 3000-5000 rpm range where it lost torque. AMD had lower HP than stock across the entire rev range. Again, OCT was the only software to remain above the stock HP curve the entire rpm range.

From the data, it appears GIAC and APR were tuned specifically for HP gains with less focus on mid-range power. APR and GIAC do get to claim to be the HP "king", however a loss in midrange power would generally result in a slower car. Based on it's consistent high torque output, OCT would probably yield the best "around town" performance yet only give up a couple of HP on the top. Nice job OCT.

Based on our findings, the APR software appeared to be trying to balance itself during runs. One run would yield high HP and low torque, then the following run would yield the opposite (lower HP with higher torque). The first run yielded the highest HP number but the lowest torque number. The 2nd run yielded slightly more torque but several HP lower than the first run. The third run yielded the highest torque number and a slightly higher HP over the previous run. However, the 4th run lost only a small amount of torque and the HP was the lowest of the run group. The software was constantly adjusting during runs, possibly trying to compensate for a massive exhaust leak in the front section of the APR exhaust.

The AMD car was an interesting case. The timing looked very good, appearing aggressive and well executed. Fuel injector duty was the highest of any of the cars suggesting it might have been running too rich and robbing the engine of power. Take a look at the AMD torque curve and note how flat it is. VERY flat. That would be a great thing if it were 30 lb-ft more but not in this case due to the unexpectedly low output. Where the losses occured remains a mystery at this point. Exhaust design? Software? An S4 with a fullback exhaust should be making a lot more HP up top than a stock car.

Seven dyno pulls were made with AMD with the later runs yielding the best power. Only two of the seven runs are included below.

Peak Wheel Torque and HP Average Wheel HP Average Wheel Torque
Wheel Torque and HP Wheel HP Wheel Torque


Dyno Detail by Tuner (alphabetical order)

AMD WHP GIAC vs Stock Torque
AMD Torque OCT WHP (res)
AMD vs Stock WHP OCT Torque (res)
AMD vs Stock Torque OCT vs Stock WHP (res)
APR WHP OCT vs Stock Torque (res)
APR Torque OCT WHP (non-res)
APR vs Stock WHP OCT Torque (non-res)
APR vs Stock Torque OCT vs Stock WHP (non-res)
GIAC WHP OCT vs Stock Torque (non-res)
GIAC Torque Stock WHP
GIAC vs Stock WHP Stock Torque
VAG Ignition Timing and Fuel Data
All Cars Ignition Timing OCT (non res) Ignition Timing and Fuel
AMD Ignition Timing and Fuel OCT (non res) Mass Air Flow
AMD Mass Air Flow Stock Ignition Timing and Fuel
ARP Ignition Timing and Fuel Stock Mass Air Flow
APR Mass Air Flow Stock vs AMD Ignition Timing
GIAC Ignition Timing and Fuel Stock vs APR Ignition Timing
GIAC Mass Air Flow Stock vs GIAC Ignition Timing
OCT (res) Ignition Timing and Fuel Stock vs OCT (res) Ignition Timing
OCT (res) Mass Air Flow Stock vs OCT (non res) Ignition Timing

The B6 S4 Dyno Shootoug was a great event to be involved in. All the cars ended up producing fairly consistent results among their runs, providing some level of comfort that no anomalous results were being reported. The ice cold temperatures and cooling fans helped keep the cars from heat soaking run after run (some even performing better after a pull or two). Even under the harsh conditions presented by a dyno, the 4.2L V8s just kept twisting out power without fuss.

Dyno services provided by:
Agile Automotive Performance
10022 York Road
Cockeysville, MD 21030

Editors Note

This article has ignited a firestorm of e-mail and feedback to AudiWorld and we wanted to take the opportunity to clarify a few points about the shootout.

Highly controlled, scientific shootouts happen from time to time in an effort to provide very concise, apples-to-apples data with which to compare tuning modifications. This article did not, in our opinion, cover a shootout of that variety, but rather the efforts of one group of enthusiasts to understand more about their own aftermarket setups.

As such, we are troubled by any claims that this article represents a comprehensive and indiputable overview of all potential B6 S4 tuning programs in the marketplace. First, while considerable effort went into controlling variables, there were a host of parameters which were not consistently addressed. Second, there are obvious tuner products missing altogether, meaning that the shootout is inherently incomplete. Third, it was not the intent of the group of enthusiasts who conducted the testing to provide an all-encompassing and 100% scientifically controlled shootout (nor was it AudiWorld intent to report the results in that manner).

To be clear, this article represents the results of a single group of Audi owner/enthusiasts using their own individual vehicles on a single day of Dynapack-based dyno testing. Actual results for individual owners with similar tuning modifications on their own vehicles could vary widely depending a multitude of factors.

We would hesitate to recommend purchase decisions for any of the products featured in this shootout, or any other competitive products which were not featured, based soley on the results of the dyno testing as presented. Until the day - which may never come - that we have a single vehicle which is tested with each and every different product in a scientifically controlled test, we could not declare ultimate winners and losers.

We are hopeful that this article will spurn a more comprehensive and inclusive B6 S4 tuner shootout which AudiWorld would be interested in covering in-depth.

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