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RPM/speed

Discussion in 'General Tech and Maintenance' started by danjones, Jun 11, 2004.

  1. danjones

    danjones Junior Member

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    On a 2003 Acura RL, what should the engine RPM be at a 70 mph cruise?
     
  2. swanny

    swanny Senior Member

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    I would guess it would be around 2,700 RPM or so, I tried finding info and found the transmission gear ratios
    Gear Ratios

    1st 2.46:1
    2nd 1.45:1
    3rd 0.95:1
    4th 0.65:1
    Final drive 3.13:1

    I think there might be a way to calculate the RPMs but I do not know the formula. If it is anything over 4k RPMs you either have your overdrive off or your transmission may have some issues.
     
  3. MikeBergy

    MikeBergy Blah blah blah....

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    Measure the outside diameter of your tire. now divide that by two. that is the tire's radius.

    Now lets say your tach says 4500 rpms, and you are in 3rd gear.

    4500 x 1/.95 x 1/3.13 = 1513.36 rpms at the tire.

    V = r(w), where r is your tire radius, and w is your tire's angular velocity( needs to be in radians per unit time).

    1513.36 x 360deg x pi/180deg = 9508.7 rad/min

    Say your tire is 2 feet in diameter - your radius is 1 ft

    V = 1ft x 9508.7 rad/ min = 9508.7 ft/min = around 108 mph. But I doubt your tires are 2ft in diameter, that seems a little big; just showing you how to do the math. There is probably a calculator in the ref section somewhere.
     
  4. Citizen_Insane

    Citizen_Insane Senior Member

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    stfu blanco. there is this thing called "Math" and it is used by lots of us to do "problems". Your problem if you can't understand elementary level mathmatics.
     
  5. Bl6CRX

    Bl6CRX Senior Member

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    woah woah cool down there hotshot...he was just making a joke...we need not turn this thread into another pointless argument, otherwise this would be looking like honda-tech
     
  6. ahedau

    ahedau Senior Member

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    ouch.. my head hurts!

    The simple answer is 2000 RPM at 70MPH given a tire size of 225/50/15. I'm too lazy to look up the OEM tire size but here's a link to the tranny calculator that does all that math for you

    tranny calculator
     
  7. MikeBergy

    MikeBergy Blah blah blah....

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    thanks. that is what I was referring to.
     
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