Someone please tell me if I am correct or not.

Using the stock 245-50-16 tires and 3.73 gear with a 700r4 tranny.

Datalog from the dyno says 6150 rpm and 118 mph. Plugging those figures into the rpm vs mph calculator:

Bowling's Vehicle RPM Calculator
Input Parameters Are the Following:
Differential Gear = 3.73 to 1
Transmission Gear = 1.00 to 1
Tire Diameter (Inches) = 25.70
Vechicle MPH = 118
Computation Results:
Computed Engine RPM is 5757

So 6150-5757=393 / 6150 = 6.39% slip
Correct or not?

 

For my formula I need

Tire diameter (yours is 25.64")
Finish line rpm at 1/4 mile
Finish line mph
Rear gear ratio = 3.73

You can't guess at what it will be without hard numbers. If you want to guess at the 1/4 mile rpm and mph as 6150 rpm and 118 mph then I calculate converter slippage at 6.214%

 

Do they have to be track numbers or can you use dyno information? I am assuming that the dyno is somewhat accurate.

 

Also, how much would posi unit slippage play into total drivetrain losses?

Could a posi unit that is close to being completely worn out rob power?

 

dup

 

- that's not entirely accurate either. - 1/4 mph is calculated, not radar/etc. Usually between about 1000 and the 1320, distance vs time it takes to cover. Some tracks take mph 30' before the finish and the stripe, some take it from the stripe to 30' after..... - that's how NHRA "slowed" top fuel down. They measure from before instead of after the finish line, thus making it look as though the cars are no longer running(continuously) over 330mph.

 

There isn't a track in North America that has a speed timer after the 1/4 mile mark since the early 70's.

The 1/4 mile speed is calculated from 66' before the finish line to the finish line. It's a simple calculation on how long it takes to break both beams. We're talking fractions of a second. A car that's set up properly will not be accellerating at a very fast pace during that last 66'. Accellerating is continually going faster. The car is already going fast but not much faster. The true speed at the 1/4 mile mark "may" be ever so slightly higher than a timeslip says. For all calculation formulas, it's close enough.

If you want to see an example of how fast your car is going at the end of the track, look at the difference in time between 1000' and 1320'. My 15 second truck travels that 320' distance in 2.5 seconds. My drag car does it in 1.6 seconds. That means my truck travels that last 66' in .5 seconds and my car does it in .33 seconds. How much faster do you think it can really accellerate in that amount of time at the top end of the track?

1/8 mile mph is more inaccurate. It's still measured from 66' before the 1/8 mile however a vehicle is still accellerating hard during that 66'.