Re: Speed Application

[Chuck Simpson <csimpson@zeltech.com>]

Okay,

Try this...

MPH = (RPM * TireDiameter) / (FinalDriveRatio * 336)
    TireDiameter = 23.08"
    FinalDriveRatio = 3.39

Some examples:
    60.79 = (3000 * 23.08) / (3.39 * 336)
    121.58 = (6000 * 23.08) / (3.39 * 336)
    131.71 = (6500 * 23.08) / (3.39 * 336)

Sounds pretty close.  Got the formula off the net.

I really don't think Wind Drag has anything to do with calculating
the MPH for a car.  It will affect acceleration.

c-ya,

Chuck Simpson
'98 White Jetta GLX-VR6


Adam Lindsay wrote:

> OKay....follow me here for a minute. I want to write an application that
> takes into account as many possible variables and calculates a realative
> distance, speed of a car run. Such an application could show prime shift
> points and speeds to expect at certain RPMs in certain Gears. I have some
> formulas now to get speed but I reliezied that Torque and Weight must be a
> contributing factor. Does anyone have these formulas laying around or know
> where I could get them.
>
> I know that there are some many factors that play into account that I could
> possible ever write an app that was perfect. The color of shirt affects how
> fast you can go. =} But I want to see how close I can get.
>
> This is what I have so far.
>
> MPH = (RPM * TireDiameter)/(Gear Ratio * 1000)
> TireDiameter = ((Section Width * Aspect Ratio)/25.4) * 2 + RIM
> Gear Ratio
> 1    3.78
> 2    2.12
> 3    1.46
> 4    1.03
> 5    .84
> R    3.80
> F    3.39
>
> so sample
> 205/50 R15 at 3000RPM in 3rd gear on a Jetta GLX
>
> TD = (205 * .50)/25.4 * 2 + 15
> TD = 23.08"
> MPH = (3000 * 23.08)/1.46 * 1000
> MPH = 47.4
> Real World showed pretty close results.
>
> But I want to study acceleration. So I need more formulas.