May 20, 2004

B5 2.7t vs. B6 4.2 Performance
Text and Pictures by:Don Pavlik

Turbocharged B5 S4 or V8 powered B6 S4?

The world got its first look at Audi's 2.7t bi-turbo engine when Audi launched the B5 S4. The engine was an immediate hit among enthusiasts with its deceptively powerful, long, flat torque curve and an advertised 250 HP (265 HP in Europe). With a simple chip/exhaust upgrade the engine was easily tuned into the 350 HP neighborhood and over 430 HP with upgraded turbochargers. Unfortunately, the 2.7t could, at times, also be prone to intake plumbing problems and turbocharger failures.

Jumping ahead to the next generation, Audi introduced the B6 S4 with a shortened version of the 4.2 liter V8 producing 340 HP right from the factory. The lightweight aluminum V8 actually comes in right around the same weight as cast iron block 2.7t, a significant improvement in the power-to-weight ratio. Advantages of the normally aspirated 4.2L: immediate throttle response as a result of eliminating turbo lag, V8 grunt, much easier throttle modulation and, hopefully, improved reliability.

Beyond the quick paper comparison we wondered how the V8 stacks up against the hard working bi-turbo V6 in daily driving? Three cars in various configurations were rounded up for testing purposes and put through their paces on a head-to-head basis (note in one case a B5 S4 was run in two different configurations). At the time of testing there were no performance upgrades for the B6 S4 V8 engine. All cars used 93 octane fuel running fuel specific programs where available.

  • Stock B5 S4 6-speed manual
  • Chipped B5 S4 6-speed manual
  • Stage II+ B5 S4 6-speed manual (chip, downpipes, full exhaust)
  • Stock B6 S4 6-speed manual

    The following data was collected assuming generally "normal" driving techniques. You won't find any clutch frying 5,000 RPM launches or power shifting in this shootout. Standing starts were done at 2200 RPM with drivetrain friendly launches. The goal here was to replicate the performance a driver wouldbe likely to achieve in daily driving.

    As such, the numbers here are sure to cause some grumbling among enthusiasts who will rise up in protest claiming that their car performs way better. Yes, all of these vehicles will achieve better times if driven to wring out absolute performance. Angry mobs, put down your brooms and pitchforks--believe it or not these are real world numbers that "Joe Average" driver is likely to achieve. No, really.

    Test conditions were in the 70's, low humidity, 87 feet above sea level. Acceleration runs were measured with a Race Logic AP-22. Engine data logging performed with VAG-COM by Ross-Tech. 

    0-100 MPH

    A quick look at the acceleration curves reveals that a chipped B5 has a leg up on a stock B6 up to a point. By 50 MPH the chipped B5 was 13 feet ahead of the B6 but started giving up distance to theB6 after 90 MPH. In contrast, the stock B5 was just left wheezing and at the back of the pack. The Stage II+ S4 was king in this crowd, having put a whopping 314 feet of distance on a stock B5 by 100 MPH! I fully expected the Stage II+ S4 to be a smidge behind from a standing start thanks to greater turbo lag, but the results clearly proved me wrong..

        0-100 MPH Standing Start
    MPH Time (sec) Distance
     (feet)
    Time 
    (sec)
    Distance
     (feet)
    Time (sec) Distance
     (feet)
    Time (sec) Distance
     (feet)

    B5 
    Stock

      B5 Chipped   B5 Stage 2+   B6 Stock  
    0 0.00 0 0.00 0 0.00 0 0.00 0
    10 0.87 6 0.73 5 0.61 3 0.74 4
    20 1.80 26 1.41 20 1.31 18 1.41 19
    30 2.67 58 2.16 48 2.00 44 2.24 50
    40 4.39 146 3.71 128 3.32 113 3.67 125
    50 5.65 229 4.76 197 4.43 186 4.97 210
    60 7.14 350 6.05 302 5.67 287 6.31 319
    70 9.56 579 8.08 496 7.52 495 8.40 518
    80 11.80 826 10.04 712 9.35 667 10.28 725
    90 14.47 1160 12.42 1010 11.47 931 12.99 1066
    100 18.23 1682 15.78 1479 14.58 1368 15.66 1439

    30-50 MPH 3rd Gear

    For 30-50, I steadied the car at 29 MPH and went full throttle. Here, lack of turbo lag for the B6 was an initial advantage against everything but the B5 Stage II+ where its huge swell of torque put it up on top again.

    The results get interesting when you factor in throttle lag. Using VAG-COM for data logging and watching throttle activity, I tracked the time between when throttle was called for and added that delay into the acceleration times. Stock programming puts the B5 at a big disadvantage, giving up a second to throttle delay thanks to boost that comes up smoothly. The two chipped B5s, with their aggressive throttle behavior, lost little time getting on-boost and ended up paying little or no penalty. The B6, like the stock B5, was hindered by the smooth power delivery behavior of the throttle.

    30-50 3rd Gear
    MPH Time (sec) Time (sec) Time (sec) Time (sec)

    B5 Stock

    B5 Chipped B5 Stage 2+ B6 Stock
    30 0.00 0.00 0.00 0.00
    40 1.72 1.55 1.32 1.43
    50 2.98 2.60 2.43 2.73
    30-50 3rd Gear with Throttle Lag Included

    30-50

    3.99

    2.88

    2.74

    3.34

    40-70 MPH Top Gear

    For 40-70 MPH in top gear, the advantage of turbocharged torque was clear. Again, the Stage II+ B5 ripped through the run over 3 seconds faster than the slowest car. The two chipped B5's all fared well as the boost came up and provided maximum torque to pull the car to 70 MPH. The stock B5 felt a bit anemic by comparison but managed to beat out the B6 all the same. The B6, out of it's power band, felt like it was struggling to reach 70 MPH.

    40-70 Top Gear

    MPH Time (sec) Time (sec) Time (sec) Time (sec)

    B5 Stock

    B5 Chipped B5 Stage 2+ B6 Stock
    40 0.00 0.00 0.00 0.00
    50 3.52 3.71 3.42 3.98
    60 6.92 6.57 5.83 7.86
    70 10.51 9.35 8.26 11.58

    40-70 MPH 3rd Gear

    Here, the group was much tighter. All the cars were in the right gear to take advantage of engine power. Again, and by this point unsurprisingly, Stage II+ B5 ruled. The stock B5 and B6 traded places while the chipped B5 edged out the stock B5 and B6 thanks to big midrange torque.

    40-70 3rd Gear
    MPH Time (sec) Time (sec) Time (sec) Time (sec)

    B5 Stock

    B5 Chipped B5 Stage 2+ B6 Stock
    40 0.00 0.00 0.00 0.00
    50 1.80 1.52 1.20 1.66
    60 3.63 3.14 2.56 3.42
    70 5.54 4.90 4.33 5.31

    Conclusion

    In this shootout the the Stage II+ B5 S4 was the clear performance king. Ripping through all the runs, turbo whistling happily under the hood, it presses the driver's back into the seat and definitely comes across as aggressive. At the other end was the stock B5, mild mannered with silky smooth power delivery compared to the other cars. While the stock B5 put down respectable times in general, it was hampered by 50 less horsepower and some 100 lb-ft less torque than the chipped B5. However we would reiterate that given the stock B5's power deficit compared to the rest of the field it did surprisingly well.

    The B6 S4 came out fighting with 86 more horsepower than the stock B5 and it showed. It was able to best the performance of the stock B5 and almost matched that of the torque rich chipped B5. The chipped B5, at an advantage with a lower curb weight than the B6 and a big fat turbo induced torque curve, still kept the B6 at bay for the most part.

    Straight from the factory the B6 is an excellent performer delivering genuine sports car performance with no fuss. Stock vs. stock the 4.2 is a substantial improvement over the 2.7t model. The chipped and Stage II+ cars are indeed faster, but if you are one who is not inclined to modify your vehicle (whether fearing warranty problems, premature failure or the cost) then suddenly the B6 performance is ano-brainer.

    From a daily driving perspective it would be an understatment to say that these cars all differ significantly. The stock B5 was the mild mannered of the group with smooth power delivery, while at the other end of the scale sat the whistling, surging, brutal and abrupt power of the Stage II+ B5. You can drive the Stage II+ B5 calmly but it's an exercise requiring constant attention. Squeeze on just a smidge too much throttle and there's the boost--whoosh--off you go at a blistering pace. The chipped B5 is also a twitchy one to drive. The B6, by comparison, was smooth and deceptive. A more than capable performer, but without the turbo surge of the B5, the B6 S4 is very easy to drive quickly without even noticing.

    Thanks to Audiworld member 8ung for providing his Stage II+ S4 for thiscomparison.

    8ung.jpg (120598 bytes)

    Test Vehicle Configurations:

    Stock B5 S4: S4, no modifications
    Chipped B5 S4: S4, APR v5.0, 93 octane program
    Stage II+ B5 S4: APR v5.0, AWE downpipes, AWE twin exhaust, 93 octane program
    Stock B6 S4: S4, no modifications

    Data logging software provided by:

    Ross-Tech, LLC
    888 Sumneytown Pike
    Lansdale, PA 19446
    USA
    http://ross-tech.com