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Quick yes/no question about sequential trannys

Discussion in 'Technical Q&A' started by YellowMaranello, Apr 5, 2004.

  1. YellowMaranello

    Jan 7, 2004
    39
    Mount Holly, NJ
    Full Name:
    Pete Gold
    Do sequential transmissions (rally cars for example) have a pedal operated clutch? Or is it like the F1 inspired transmissions in F cars?
     
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  3. formula1joe

    formula1joe Formula Junior

    Nov 3, 2003
    436
    Atlanta, GA
    Full Name:
    Joe Bennett
    I believe there is no clutch. Just pull and go!
     
  4. Sean F.

    Sean F. F1 Rookie

    Feb 4, 2003
    3,003
    Kansas
    Full Name:
    Sean F
    Yes, they have a clutch.

    Just like Motorcycles and Indy cars. You can operate the transmission without the clutch if you match revs carefully and practice, but in general it's not a good idea to do that on your street car.
     
  5. Smiles

    Smiles Moderator
    Moderator Owner

    Nov 20, 2003
    14,390
    Pittsburgh, PA
    Full Name:
    Matt F
    Not true.

    Skip Barber's Formula Dodges, for example, have a sequential gearbox with a normal pedal layout, including the clutch. The clutch is used for starting from a standing stop, or for downshifting.

    Up shifting does not require the clutch. Under full acceleration, you put pressure on the gear lever towards the direction for an upshift. Lift off of the acelerator pedal slightly, and the transmission will click into the higher gear, and you can continue accelerating.

    Down shifting requires the clutch. Because the transmission is sequential, you can't put it into neutral when going from, say, 5th to 4th. The clutch is necessary to rev the engine in order to find the lower gear.

    --Matt
     
  6. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
    Full Name:
    Rob Schermerhorn
    Matt, you're well versed in dog synchro 'boxes. Done a Skippy or two?

    Everything you stated is correct.

    Slight addition that race school instructors won't tell you 'cause it may cost them increased maintenance costs: All dog drive gearboxes Can be downshifted without depressing the clutch pedal. The technique requires practice. What must happen is a very slight blip of throttle followed in microseconds by the gear lever going into the lower gear. The driver must blip to take the load off the dogs momentarily to accomplish the shift down (which is why one must lift for an upshift, takes the torque off the gear syncros). Depressing the clutch for this takes most of the skill out and keeps the driver from grinding expensive dog ring synchros and gears.

    Some drivers prefer to hit the clutch, and some designs work better than others. Knowing the RPM drop between gears is helpful, though it's also safe to assume the RPM drops decrease as you go up. Example: 2500 rpm drop from 1st to 2nd, 2000 2nd to 3rd, 1400 3rd to 4th, 1000 4th to 5th. Depends on the track and torque / hp curve of the engine. Too much RPM from a big blip is as bad as not enough.


    Best regards,

    Rob Schermerhorn
     
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  8. NC348

    NC348 Karting

    Feb 18, 2003
    154
    Houston, TX
    Full Name:
    James I. Movich
    Hey Pete....
    didnt you know there is no such thing as quick, yes, or no here? Ha! (well, we DO have maybe sometimes...)

    we do have detailed, informative, thorough, and lively, even opinionated, but, alas, none of the above .....LOL
     
  9. Smiles

    Smiles Moderator
    Moderator Owner

    Nov 20, 2003
    14,390
    Pittsburgh, PA
    Full Name:
    Matt F
    Sequentials don't have synchros! (But I know what you mean.) :)

    Thanks, Rob. I'll have to try downshifting like that!
     

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