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355 Differential

Discussion in '348/355' started by bostonmini, Jan 21, 2004.

  1. bostonmini

    bostonmini Formula 3

    Nov 8, 2003
    1,881
    Someone a few weeks ago brought up the fact that the 355 from Switzerland has a slightly more aggressive final drive due to the extreme alititudes. If thats the case, has anybody ever documented the performance gains for a normal environement? I would think that might actually be a really nice little mod eh? I think it went from 4.35 to 4.55 but not sure...
     
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  3. redhead

    redhead F1 Rookie
    Consultant

    Dec 26, 2001
    4,869
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    ~Red~

    Can you point me to this post?? I have no idea where to start looking. Very intrested in this.

    Thanks

    R
     
  4. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,014
    That was I.

    But I reitterate (again), the swiss gearbox has LOWER performance not higher. The swiss noise laws made Ferrari giggle the ratios to turn fewer RPM/speed and thus have less thrust, less RWTQ and therfore lower acceleration and LOWER performance.

    LOWER not higher. LOWER.

    Got it? LOWER!

    I responded twice after I gave the indication this it might be higher performaning, then I looked in the shop manual and found I was wrong and stated sow in two different responses in the original thread. Apparently you can't read.

    LOWER PERFORMANCE not higher.

    Got it now?
     
  5. rudy

    rudy Formula Junior

    Jan 13, 2004
    360
    Los Angeles California
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    Rudy Hassen
    So you're saying it's lower. Right?
     
  6. bostonmini

    bostonmini Formula 3

    Nov 8, 2003
    1,881
    "apparently you can't read"


    so you never forget? better man than I...
     
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  8. redhead

    redhead F1 Rookie
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    Sorry to get in the middle of this...BUT, the reason I asked, I can not find any info on this either way, higher or lower. I looked in all of my F355 parts books and Cd's and only in the Challenge book did it note anything about the CH cars. And its ONLY note was, Ch cars are listed as Europe cars in the diff. section.

    I am not saying I doubt anyone, just a little curious as to what the part #'s for the CH cars may be.
     
  9. bostonmini

    bostonmini Formula 3

    Nov 8, 2003
    1,881
    Mitch, lost my temper, no disrespect, I couldnt find the old thread to be honest;) Although, a more aggressive rear end is interesting as an idea...
     
  10. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,014
    Page D-18 Istruzioni per le Riparazioni :: Volume 1 F355 - F355F1 Repair manual. Section: Gear ratios:

    Spur rear ratio
    Standard: 25/29
    Swiss: 25/27

    Overall gearing:
    1st gear:
    Standard: 13.327:1
    Swiss: 12.408:1

    Less torque multiplication in the swiss gearset.
     
  11. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,014
    Most of the time, but especially in Switzerland!
     
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  13. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,014
    I sort of figured that, carry on.
     
  14. SoftwareDrone

    SoftwareDrone F1 Veteran
    Rossa Subscribed Owner

    Jan 19, 2004
    6,298
    San Jose, California
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    Mike
    I tell you, when I changed the final drive in my NSX from the 4.09 to the 4.55, it TOTALLY TRANSFORMED THE CAR! It was WAY more fun to drive, and I was smoking cars I could barely keep up with before during light to light races. Yes, I really want to know more about this mod as well.

    :)
    Mike
    http://northwest.nsxca.org/mike.html
     
  15. bostonmini

    bostonmini Formula 3

    Nov 8, 2003
    1,881
    Very interesting on the NSX, I used to be on that board a while ago, along with the s2ki board which made me think about it. Ferrari's are more beautiful, but are still clearly very much performance machines, and if we can raise the bar that much more by WHATEVER means, Im sure enzo would be proud;)
     
  16. redhead

    redhead F1 Rookie
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    Dec 26, 2001
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    Mitch--

    Not doubting you at all, it is just confusing to me, as you have number and the F355CH book even states that there is a difference for the CH cars, YET, no where are the different part(s) listed. And being a parts *****, you see why I am digging on this. It's slightly boggling to me that they do not show a difference for the CH cars, but once again, thats Ferrari :)

    R
     
  17. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
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    Rob Schermerhorn
    I have no documentation on Challenge having different gearing for F355. My spreadsheets I used back then have standard gearing for USA cars.

    The confusion may come from the fact that for 348 Challenge, non factory built chassis (dealer conversions) were authorized to use the Speciale drop gear. For 348, there are three different drop gears available, standard 348 (tallest), standard Mondial T (intermediate, no one used it in Challenge), and Speciale/ Spider/ Factory Challenge (shortest, we all used it). Somewhere in my archives I have the actual ratios if someone's interested.

    So, if you want to change gearing in a F355, I can get new gears, specifically designed for F355 gearbox. What's your goal?

    I'll supply cost and availability details depending on the project. Complete dog-drive synchro conversion? No problem. Custom drop, no problem. Depending on the specifics, I can have parts in as little as six business days. Let me know now, and I'll have specifics by next Monday.

    Best regards,

    Rob Schermerhorn
     
  18. redhead

    redhead F1 Rookie
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    Dec 26, 2001
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    Rob,

    What I am asking is why there is no listing for factory gears for the CH cars? Look in the 97 Challenge book page 8 and it list that there is a differnce between the CH cars and the rest of the world. I have no real intrest into purchasing them, just trying to get to the bottom of where it may be listed. As well, I can source the gears myself if I ever did need them.
     
  19. ze_shark

    ze_shark Formula 3

    Jul 13, 2003
    1,273
    Switzerland (NW)
    Interesting, so swiss 355's have 7.4% taller gearing ? This is huge. 500rpm at advertised top speed (assuming that the 295km/h can be reached with such a taller gearing).

    This spiked my curiosity so I went on reading swiss regulations on noise emissions (for amateurs http://www.admin.ch/ch/f/rs/7/741.41.fr.pdf, enjoy).

    Unless I missed something, swiss noise regulations only call for static measurements, made at 3/4 of the peak power rpm (422.1 p207), 7m away from the car. Not a rolling noise test.

    A short digression: this does not help me to understand why Ferraris have this vacuum valve system since the noise measurement level is much higher in revs than 3500rpm.

    Why would Ferrari go to the extent of having a taller final gearing if noise measurements are static ? Would not see exhaust emission laws impose that since they are static too.
     
  20. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,014
    There is a resonance in the header systems between 2500 and 3500 where strangling the exhaust leads to smoother performance. At this point, the engine is turning slo slowly that the negitive pressure wave from the header has abated before the intake valve opens, and the subsequent positive pressure wave blows fresh air back up the intake. The exhaust valve strangles the headers so both waves are reduced in pressure. Once the revs rise above this region, the headers add performance, so the valve is opened for full wave action in the headers.

    The exhaust valve is present to prevent performance issues not to avoid noise issues.
     
  21. ze_shark

    ze_shark Formula 3

    Jul 13, 2003
    1,273
    Switzerland (NW)
    Thanks for the info Mitch, very interesting.
    That means that the wise guys who bypass the valve so that it's open all the time are missing the point ? Same thing on a 550 ?
     

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