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Acceleration vs percived GForce

Discussion in 'Model S: Driving Dynamics' started by mochouinard, Aug 31, 2014.

  1. mochouinard

    mochouinard Member

    Joined:
    Aug 3, 2014
    Messages:
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    Location:
    Montréal, Quebec, Canada
    Hi,

    I normally can answer those answer by myself, but I'm confused for some reason on this one !

    Let say we have 3 car. One that does 0-100kph in :
    A: 4 second
    B: 5 second
    C: 6 second

    Would the actual difference force perceived between the B-C and A-B be the same, or the A-B would feel much more.

    So is the acceleration calculated in time from 0-100 offer an linear g-force difference or it exponential as the time decrease ?

    As you probably guessed, it to decide if the P85 would be worth it feeling wise, or the S85 would be just fine and save some hard earned cash !
     
  2. Xenoilphobe

    Xenoilphobe Active Member

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    Fairfax County Virginia
    A = A Navy Fighter Jet launched off a steam catapult system of a Carrier Deck
    B = A Roller Coaster on it's steepest sloop
    C = Most high performance ICE Cars.

    I wish I knew how to really answer your question.
     
  3. brianman

    brianman Burrito Founder

    Joined:
    Nov 10, 2011
    Messages:
    15,487
    From a web search of "feel of g force compared to acceleration":
    How many G's does a car pull under acceleration? - PistonHeads


    - - - Updated - - -

    If finances are a significant concern (only you can decide), then get the S85 and you'll love it.
    If you have some "fun" money to work with (finances have some breathing room), the P85 is even more addictive.

    Not sure I helped, but the main point is that you'll love either vehicle. I don't "miss" the P when I get an S85 loaner. Heck, even an S60 loaner (I've never driven a 40/60 ... hint hint beg ....) is a better loaner vehicle than anything Enterprise has in their fleet, IMO.
     
  4. physicsfita

    physicsfita Member

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    Ann Arbor, MI
    Assuming constant acceleration, a = Delta v/Delta t. Convert km/h to m/s, and divide by g = 9.8 m/s^2 to get g's of acceleration. Since I'm waiting for a very long download to complete, I did the math for you: :biggrin:

    A: 0.71 g
    B: 0.57 g
    C: 0.47 g

    The acceleration won't be uniform, though. As you speed up, air resistance will be working the other way, and the car's acceleration will decrease. But, my download is now complete, and I don't have to time to do the differential equations. :redface:
     
  5. R²B

    R²B All Star

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    Waddell, AZ
    So....I'll use 60mph instead of 100kph.

    Car 1: From 0 to 60mph in 4s (assuming constant acceleration) = 88ft/s in 4s or 22ft/s^2 of acceleration
    Car 2: From 0 to 60mph in 5s (assuming constant acceleration) = 88ft/s in 5s or 17.6ft/s^2 of acceleration
    Car 3: From 0 to 60mph in 6s (assuming constant acceleration) = 88ft/s in 6s or 14.6ft/s^2 of acceleration

    The acceleration due to gravity (G-Force) is 32ft/s^2 so we have:

    Car 1: .68 g
    Car 2: .55 g
    Car 3: .45 g

    You'll notice that the G-force starts dropping more and more rapidly due to the fact that we're using ratios and linear changes in time reflect exponentially.
     
  6. astrotoy

    astrotoy Member

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    SF Bay Area
    The big Tesla grin comes to a large degree from the instantaneous acceleration of the 1 speed motor applying the torque to the wheels. The assumption of constant acceleration in the calculations does not take the difference in the initial acceleration of a Tesla Model S (any of the models) compared to a normal ICE. My Lexus LS460L has exactly the same 0-60 time spec as my Model S85. However, the acceleration characteristics are completely different, a big grin with a Tesla, not so much with a Lexus. As far as the differences among the S85, P85 and P85+, I would just do a test drive to see whether it is worth it to you.
     
  7. mochouinard

    mochouinard Member

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    Location:
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    Thanks Guys, you guys answered my question ! Made this small graph :
    gforcegraph.png
    So starting at 6second and down, the increase start to be considerable more. Is the diff between worth while... Ok maybe this info doesn't help me much ! :) I'll hope to be able to do a S85 and a P85 model test drive close together !
     
  8. Hans (Amsterdam)

    Hans (Amsterdam) Model S res#3130

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    S85 torque is 440 Nm from 0-5900 rpm, P85 torque is 600 Nm from 0-5300 rpm.
    G force of the P85 is 600/440 = 1.36 times G force of the S85 (from 0-5300 rpm).
    So off the line this is quite a difference, except when driving on wet roads. Above 5300 rpm the difference gets smaller.
    My experience is that above 50mph (from 6.500 rpm) the difference in acceleration between P85 and S85 is marginal.
    I drive a S85 for 9 months now and I am still impressed by its acceleration.
    If you like a comfortable ride: don't go for 21 inch wheels.
     

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