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Use of Tachometer for Speed Control

Discussion in 'Ferrari Discussion (not model specific)' started by Rachane, Oct 6, 2005.

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  1. Rachane

    Rachane Formula 3

    Sep 5, 2005
    1,086
    San Francisco, CA
    Full Name:
    Rachane
    #1 Rachane, Oct 6, 2005
    When driving my 328 I had some difficulty keeping the car's speed steady, as the marks on the speedometer are very close together and a slight touch on the accelerator is enough to alter speed 10mph or so - hardly noticeable to the driver, but possibly more so to a lurking radar gun.

    I found that it was much easier to use the tach to keep speed constant. For example, 3,500rpm in 5th gear yields a nice, steady 65mph. 3,000rpm 60mph, 2,500rpm 45mph, and so on.

    Just thought I would pass this along as a possibly useful technique ... at least for those who don't always have both dials pegged all the time! :D
     
  2. Bandit

    Bandit Formula Junior

    Dec 21, 2003
    493
    Central MS
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    Mike B.
    #2 Bandit, Oct 6, 2005
    I use the tach, but it is because the steering wheel hides everything from 40 - 120 mph. Just under 3K means everything is fine on the two lane highways the cops like to frequent.
     
  3. Mondial2

    Mondial2 Karting

    Jan 23, 2004
    60
    #3 Mondial2, Oct 6, 2005
    I use the tach because the speedo doesn't work about 50% of the time!

    The speedo has been rebuilt, but it turned out not to be the problem. Apparently the sending unit needs to be replaced. I wish I had tried that first!
     
  4. hardtop

    hardtop F1 World Champ

    Jan 31, 2002
    11,294
    Colorado
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    Dave
    #4 hardtop, Oct 6, 2005
    I always use the tach because the speedo is off anyway and harder to read. However, your numbers are off. In a 328, in 5th gear, you get roughly 20MPH/1K on the tach. 3K for 60 is about right, but 3500K is 70 and 2500K is 50.

    Dave
     
  5. docweed

    docweed Formula Junior

    Dec 8, 2004
    452
    Morgantown,WV
    Full Name:
    Chuck Stewart
    #5 docweed, Oct 6, 2005
    I'll have to try that as my speedo is in kilometers and it's too much mental gymnastics multiplying by .62 for all possible speeds. BTW I checked about having my speedo converted but you can only change the mile/hr and not the odometer. Something to do with the electrical impulses.
     
  6. Rachane

    Rachane Formula 3

    Sep 5, 2005
    1,086
    San Francisco, CA
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    Rachane
    #6 Rachane, Oct 7, 2005
    That's interesting. In this 328 and the previous one I had some years back, 3,500rpm/5th showed 65mph. I suppose the test would be to get the speedometer calibrated; I wonder if anyone has had this done for a 328 or other Ferrari. I had it done some time ago for a Maserati 228, in which the speedo from the factory was substantially off.

    To date I have been using 3,500rpm for 65mph on CHP-prowled California highways and haven't had any problems. To be sure, on these same highways the prevailing trafffic is usually going 80-90, so I guess I'm chump-change.
     
  7. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,044
    USA
    #7 f355spider, Oct 7, 2005
    328 tachometers are well known to fail and start reading lower rpms than actual. You can send it to Palo Alto Speedometer for repair.
     
  8. venusone

    venusone F1 Rookie

    Mar 20, 2004
    3,238
    #8 venusone, Oct 7, 2005
    Was that in your Bandit Special or the 328. Gotta love that American muscle in black & gold! Hey, I was in a movie w/ Burt.
     
  9. Bandit

    Bandit Formula Junior

    Dec 21, 2003
    493
    Central MS
    Full Name:
    Mike B.
    #9 Bandit, Oct 8, 2005
    That's in the 328. The T/A has a tilt column (something I guess Ferrari couldn't figure out) so I can put the wheel where it is most comfortable and still see the dash. 3K in the T/A would be closer to 90 mph, and I doubt the cops are that forgiving.

    You'll have to let me know where in that movie you are. I'll be sure to watch closely next time.
     
  10. icantdrv55

    icantdrv55 Karting

    Aug 13, 2005
    189
    Hartfordish, CT
    Full Name:
    Chris
    #10 icantdrv55, Oct 8, 2005
    Someone mentioned to me that Ferrari speedos are notoriously inaccurate (we were talking about my 328 at the time -- I don't know if this is true for all Ferraris...), and that they usually overstate the actual speed. This conversation sparked my curiosity, so I brought my GPS with me on one trip, and discovered that when my speedo reads exactly 80MPH, I'm actually going 72. Haven't yet gotten geeky enough to figure out how linear the error is...
     

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