Downshifting multiple gears with semi-automatic transmission

Discussion in 'Motorized Vehicles' started by iNoob.x, Nov 29, 2010.

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  1. iNoob.x

    iNoob.x Notebook Evangelist

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    Hi everyone,

    This is probably not the best place to ask this but I thought someone on NBR's GOT to know the answer. I've been reading up on cars lately and was looking at semi-automatic transmissions (automated manual transmission) where you shift using paddles behind the steering wheel or the lever (with an up/down motion). I currently drive a standard and sometimes when I suddenly want to go fast I can downshift 3 gears - from 6th to 3rd (or 6th to 4th if I'm on the highway to avoid the engine blowing). Anyway, long story short, how do you downshift more than one gear at a time using the paddle? Do you just press the left paddle twice? Wouldn't that be a little jerky since it would: clutch, downshift, try to release clutch but realize you've pressed the lever again, reclutch, downshift, release the clutch? :confused:
     
  2. linuxwanabe

    linuxwanabe Notebook Evangelist

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    Dual clutch transmissions are entirely sequential and can't skip gears. Old fashioned torque converter automatics can, but I'm not sure that the manumatic interface allows you to do so? Actually, these days you're just better off leaving it in "Drive."

    True automated manual transmissions, that is manuals where a conventional clutch is worked by a servo, should be avoided. The shifts are simply too slow and jerky. This is precisely why Ferrari, Maserati and BMW have moved to dual-clutch transmission.
     
  3. H.A.L. 9000

    H.A.L. 9000 Occam's Chainsaw

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    ^True. I can go directly 2 gears down at a time. Three isn't supported by the TCM software, as it would place the RPM's to high to handle rev-matching and gear switching safely. That's BMW's Steptronic in Sport mode. My Camero didn't support anything like that... and it was the 6Spd automatic.
     
  4. Trottel

    Trottel Notebook Virtuoso

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    Two downshifts in a row aren't any more jerky than one. It shifts then shifts again.

    This is all academic though, since real drivers choose manuals. Then you can go from reverse to sixth all in one shot and as smoothly as you want/can.
     
  5. H.A.L. 9000

    H.A.L. 9000 Occam's Chainsaw

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    A good Steptronic or Lexus's 8-speed are quicker than a manual, even for professional drivers. Manual's with a really good driver are great, but recent technology has put some autos on the same level, with even quicker shifts. And gearboxes like in the Nissan Z even do rev-matching for gear selections... which is nice for the everyday joe that doesn't drive like a pro..lol.
     
  6. Trottel

    Trottel Notebook Virtuoso

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    I'm well aware that there are slushboxes like the one you have that can be relatively close to the performance of a manual, and that there are a number semi-automatic transmissions that are decidedly superior to manual transmissions from a performance standpoint, but it isn't about that.

    PS: BMW's Steptronic automatic transmission is significantly slower than a manual by about 10% according to the 0-60 times they give on their website. Also there is no way to compare Lexus's automatic that you are talking about since there is no manual transmission to compare it to, but there is no way it is faster than a manual anyway. No conventional automatic is going to offer superior performance to a manual transmission. Sure, the automatic may possibly be able to shift as fast or even slightly faster than a manual, but they have other performance penalties over a manual transmission. Only semi-automatic transmissions often, but not always, have greater performance than manuals, but they are unrelated to conventional automatics.
     
  7. Ferrari

    Ferrari Notebook Evangelist

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    I dont know about other cars that use F1 type transmissions but IIRC, when down shifting in a Ferrari you hold down the left paddle shifter down when slowing down and the ECU automatically downshifts and to also avoid over revving.

    I just also want to say that Ferraris F1 superfast transmissions are far superior to any manual than any other sequential type transmissions in any production car. According to Ferrari, the gear shift times on the 458 is zero. Through my research, the only thing that the standard manual currently has over the F1 transmission is reliability and has a longer service life. But from what i have read, its debatable in the Ferrari community.
     
  8. H.A.L. 9000

    H.A.L. 9000 Occam's Chainsaw

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    True, true. Performance vs Fun... the manual wins EVERY time. The Lexus transmission I remember because it's the same one used in the LF-A, and while it's not Ferrarri "0" shift times, it's rev-matched and the maximum shift time is about 350MS. That's pretty quick, especially for something used in production cars. The LS has the same transmission. :)
     
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