You may recognize this car--we tested a K&N drop-in filter, MagnaFlow exhaust, Stratmosphere downpipes sporting high-flow cats and Revo software on it once before. With those mods power jumped from 321 whp to 341 whp (Feb. ’10).

Since then, the car’s been running great but the owner’s been thirsty for more. With only one aftermarket RS4 intake system available that we know of, we ordered a GruppeM Ram Air system from Modified by KC. Whether it would make any more power than the K&N drop-in we didn’t know (we didn’t think so), but we were curious enough to try. The trick with dyno testing an RS4 is in monitoring fluid, ambient and intake air temperatures, which have to be the consistent from run to run. This allows the ECU to trigger the same, and optimal, ignition timing and fuel mixtures. We monitored these parameters using an Actron Elite AutoScanner Pro CP9185 scan tool. Our scanner was also used to monitor temperatures during our 60-120mph pulls, ensuring accuracy, and the times were recorded using the GPS-based PerformanceBox from VBox USA.

Vehicle Data

Engine: 4.2-liter V8 FSI
Transmission: Six-speed manual
Mileage: 16,450
Current Modifications: Milltek/Stratmosphere downpipes, MagnaFlow cat-back exhaust, Revo Technik Stage 2 software, Continental ContiSportContact 3 tires, Forgestar F05 wheels
Dyno Data: Dynojet 424x
Temperature: 75-82 F
Humidity: 10-16%
Test gear: Third

Peak power: 341.9 hp @ 7500 rpm
Peak torque: 296.7 lb-ft @ 3800 rpm
3000-8400 rpm dyno acceleration: 8.74 sec.
Temperature: 75 F
Humidity: 16%

Test Notes
To retest the K&N with the car’s current mods, we returned the intake back to its stock paper element for a new baseline. Like other newer cars, the RS4 goes through a lot of ECU adaptation on the dyno. With similar temps, the runs started off in the upper 320 whp range and finally reached the 340 range consistently, but not until after 10-12 runs. We knew we’d have to give several runs and about an hour’s worth of pulls for each upgrade when taking cool-down time into consideration.

This was the highest number we got so we went with it as our baseline. We were surprised to see almost the same horsepower we left off with from over a year ago, when we also had a K&N drop-in filter installed.

K&N Drop-in Filter

Test 1

Peak power: 352.7 hp @ 7200 rpm
Peak torque: 303.2 lb-ft @ 3800 rpm
Max horsepower gain: 16.0 @ 6700 rpm
Max torque gain: 12.5 lb-ft @ 6700 rpm
3000-8400 rpm accel.: 8.52 sec.
Temperature: 79 F
Humidity: 10%

Parts: K&N drop-in filter
Installation time: 0.5 hours
MSRP: $69


  • Great bang for the buck
  • Cons

  • Considering the inexpensive price, none
  • Test Notes
    In Part 1 (Feb. ’10) we tested this K&N filter, only with the stock exhaust system and the Revo Stage 1 software. It netted a peak gain of 10.2 hp and 7.0 lb-ft of torque at 7500 rpm. This time, with the current exhaust mods and Stage 2 software, the filter was good for a little more power.

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