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  1. #1
    Active Member One Ring
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    Sep 22 2016
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    Kapaa HI

    D2 S8 Motor vs B7 S4 Motor Difference in HP/TQ

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    Hi all, So 4.2 V8 in the D2 S8 & B6-B7 S4 appear the same except the timing components of course.

    Why does the S8 have a little more HP and Torque? They are almost identical numbers so if anyone knows what gives the D2 S8 a little more HP/TQ rating from Audi I've always wondered?

    Thanks in advance!

    Eric,

  2. #2
    Veteran Member Three Rings jmcS4's Avatar
    Join Date
    Nov 16 2013
    AZ Member #
    130459
    My Garage
    Nogaro B6 S4 & Brillant Black B5 A4 Avant
    Location
    Lower NH

    They do not look the same from the engine bay. Different intake manifolds and probably heads, cams etc.


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    04' B6 Nogaro on Nogaro S4 (Current)
    04' B6 Nogaro S4 (parted out)
    01' B5 A4 Avant 1.8t (current DD)
    00' B5 A4 Avant 2.8l (sold)
    04' B6 Silver S4 (totaled)
    98' D2 A8 (junked)

  3. #3
    Active Member One Ring
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    Sep 22 2016
    AZ Member #
    381553
    Location
    Kapaa HI

    Yes, that's what I Thought, the different intake and cams could make the difference alone. Just always wondered as there so close in HP & TQ ratings. And both 4.2 5 valve heads.
    When the B6 S4 came out some car rags were saying how the stuffed the S8 or S6 motor in our cars by shortening the block by going from belts in front to chains in the rear of the motor.

    Thanks for the info!

  4. #4
    Veteran Member Four Rings Nollywood's Avatar
    Join Date
    Nov 03 2011
    AZ Member #
    83391
    My Garage
    B6 Avant 420-R, Toyota Runx 1.4 16V
    Location
    Manitoba, Canada.

    They are not close in terms of power.

    B6 S4 4.2 V8 40V - 344hp.
    D2 S8 4.2 V8 40V - 380hp.

    Both have the same peak torque of 430Nm.

    Both have dual-stage intake manifolds.
    Both have the same exhaust manifold volume and shape, just different flanges on the ends.

    Camshaft are different, and I donít mean the drive configuration (chain vs belt). Different profiles, the S8 cams are geared towards more torque from lower rpm, to suit the heavier car and luxurious drive experience.

    The main differences are in the ECU maps, as all things being equal, both engines will produce the same power and torque, at the same engine speed.
    His:
    B7 420-R Avant - RS6 4.2 BiTurbo, (BCY). B7/8.5 Hybrid "RS4" OEM Widebody Coming Soon.

    Waiting To Purchase 2012 B7 Seat Exeo ST Sport Tech.

    Hers:
    2002 Toyota Runx, 1.4L DOHC 16V Auto.

  5. #5
    Active Member One Ring
    Join Date
    Sep 22 2016
    AZ Member #
    381553
    Location
    Kapaa HI

    Cool

    Thanks for the info- on the differents in Hp TQ in the US model anyway it says D2 S8 @ 360HP@ 7,000rpm 317@ 3,400rpm for torque. VS B6 S4 340Hp @7,000rpm & 302 @ 3,500rpm for torque.

    So, Yes different camshafts & different ECU would make sense, as you stated for the top of the line S8 flagship Audi at the time- heavier & more expensive Luxurious car.

    I would love to have both! But am more then happy with my B7 S4.



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