2 speed transmission data thread

Discussion in 'General Topics' started by gwestr, Sep 1, 2019.

  1. gwestr

    gwestr Active Member

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    A two speed transmission could be a game changer for an electric car, or it could be a warranty and reliability nightmare that takes your million mile car with a 500,000 mile battery and puts it in the shop every 50,000 miles, like a classic VW Group DSG.

    First, we need to map out the gear ratios. Second, we need to figure out at what RPM it cuts over, or what the gear change strategy is.

    Let’s start with Tesla as a reference. I am under the impression the Tesla PSM is 19000 RPM max, electronically limited to 155 MPH (below max RPM), it has a 7.5:1 gear ratio, and it may or may not have a gear-reduction-ratio before connecting to the wheels. The latter is how Tesla slows down the launch of an AWD car, versus a Performance AWD car.

    I would think the Porsche system has two purposes. First, to act as an overdrive at 80 MPH and improve efficiency. Second, as a way to separate the “launch gear” from the “track gear”.
     
  2. JC Mann

    JC Mann Member

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    I thought I read an article that said 2nd gear kicked in at 125, which means I’d never see it.
     
  3. 285kph

    285kph Member

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    Your troll act is really tiresome.
     
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  4. 285kph

    285kph Member

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    Hm. For the quoted sub-10s 0-200km/h time (from the "Fully charged" video), some of the Taycan's supposed advantage vs the P100D was attributed to the 2-speed gearbox. If it shifts at 125mph (201km/h) that wouldn't seem to help.
     
  5. OP
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    gwestr

    gwestr Active Member

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    I instruct with the Audi group. Many participants end their track weekend early because of DSG failures, including some students I had. And it’s not the cheap cars either, many times it’s the high powered cars like RS5. And not tuned either, stock.

    A transmission can goose EV performance numbers and “beat Tesla” but at the cost of adding massive complexity and decreasing reliability. This is a reasonable statement to make. VW Group is “first” here and nobody else has done this, so we should question why.

    I’d like to know some details on the transmission. Does it use clutches? Again, this would be a first for EV. It does feel like a step backwards from a simplicity standpoint.

    An EV makes so much power that everything is under stress. Hell, the Tesla wheels untorque themselves (129 lb/ft spec) because the launch is so brutal.
     
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  6. Friedrich

    Friedrich Well-Known Member

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    Yes.....he constantly comments about Daddy's car. The bad part of the internet is that children participate when you want intelligent mature discussions. I too am a big Tesla fan, but I don't like childish trolling.
     
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    gwestr

    gwestr Active Member

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    Tell me your thoughts on WeWork. You scared they’re going to put your lights out? I heard Adam’s dad gave him the money.
     
  8. Rotordude

    Rotordude Well-Known Member

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    Transmission on an EV? I thought the marketing material/ website for the mission E just shows the battery pod and two motors...like the Tesla and Etron?
     
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    gwestr

    gwestr Active Member

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    Update: the 2 speed transmission is on the rear axle only.

    I believe there is a trick dual motor EVs do where they can turn off one motor at high speed. On the Tesla, I believe the front wheels do the pulling on the highway. It would sort of make sense to me to use different fixed gear ratios on either axle, to balance performance on launch with economy at speed.
     
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  10. charliemathilde

    charliemathilde Well-Known Member

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    Yes that’s how the dual motor Teslas use different gear ratios. I can’t wait for the world where every wheel gets its own motor like Rimac. You know, just not for $2m ..
     
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  11. JC Mann

    JC Mann Member

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    While it is true Taycan can adjust the amount each axel is used for range vs. acceleration, the Taycan actually has 2 gear ratios for the rear motor - a low one for gas faster acceleration and a higher one for better range.
    Teslas have only one gear ratio.
     
  12. JC Mann

    JC Mann Member

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    Look at wired.com/story/electric-car-two-speed-transmission-gearbox
     
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    gwestr

    gwestr Active Member

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    Wow, it actually says reliability will be a problem. No thanks!
     
  14. Friedrich

    Friedrich Well-Known Member

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    LOL.....the article said TESLA had reliability issues when it tried the 2 gear system in its first Tesla Roadster.....LOL

    For an everyday car, you don't need the two gears, for a sports car you will. I don't have issues when companies try something new and initially have problems. Thats called market leadership and then others follow. ike Porsche's PDK in ICE vehicles......the automatic double clutch. The Model S couldn't even run a 3.3 mile race track at top speed in 2016 because of battery temperature control issues, but hopefully now Tesla has improved and will be able to run a 12 mile track a top speed. I am a big Tesla AND Porsche Fan.....l

    I will bet money that the Tesla Roadster 2 will have a 2 gear system. And the Roadster 2 will be an absolutely amazing car!! Hopefully Tesla is spending as much effort in engineering on steering and stability control for the Roadster, and that technology will be used on the Y and a long overdue revamped Model S!
     
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    gwestr

    gwestr Active Member

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    I got some more data. The Porsche PSM motor has a serious problem with the torque band. The only way they could ship it is with the 2 speed. Tesla has a far superior peak torque band from 1 RPM to 8000 RPM.
     

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