The 4.2 liter FSI V8 is a great motor but not exactly a tuning powerhouse platform. Unfortunately, as the motor is fairly highly stressed in stock form and routing power to all four wheels without going forced induction on the motor there is not much to gain. On 93 octane APR takes the car from 352 horsepower at all four wheels to 361 horses at all four wheels for a gain of only 9 horsepower at the wheels.

This improves on 100 octane to a gain of 14 horsepower at the wheels for a peak of 366 all wheel horsepower. As sad as it is to say, the S5 with the 3.0 TFSI supercharged six cylinder makes more sense as a tuning platform than the 4.2 V8 in the RS5. When APR releases a supercharger for the B8 RS5 things may change. Still, a naturally aspirated V8 with an 8400 RPM redline is pretty sweet and if one wants a little more out of it APR's tune is a good place to look especially for $699.

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Stock
As Measured by Audi
Stock - 93 Octane (R+M)/2
As Measured by APR
91 Octane (R+M)/2
95 Octane RON
93 Octane (R+M)/2
98 Octane RON
100 Octane (R+M)/2
104 Octane RON
Rev Limit 8400 RPM 8400 RPM 8400 RPM 8400 RPM 8400 RPM
Speed Limit Max Speed Limited Max Speed Limited Unlimited Unlimited Unlimited
Peak Horsepower (HP) 450 HP 450 HP Uneasured 458 HP 466 HP
Peak Torque (FT-LBS) 317 TQ 324 TQ Uneasured 330 TQ 335 TQ
Max Horsepower Increase over Stock

Uneasured 10 HP @ 3250 RPM 18 HP @ 7150 RPM
Max FT-LBS of Torque Increase over Stock

Uneasured 16 TQ @ 3250 RPM 16 TQ @ 2350 RPM
Program Mode 0-60 MPH 0-100 MPH 60-120 MPH 60-130 MPH
Data collected at the same location via a Racelogic P-Box with 93 (R+M)/2 fuel, launch control, ESP/ASR off, Dynamic mode and Sport mode. May not be comparable to data collected in other locations.
Best Measured Stock - 93 (R+M)/2 Octane 4.3 seconds 9.8 seconds 9.1 seconds 11.7 seconds
Best Measured APR Stage I - 93 (R+M)/2 Octane 4.0 seconds 9.1 seconds 9.0 seconds 11.3 seconds