Converter Slippage

[Mad_Trbo]

To calculate converter slippage using the following formula:

Conv Slip% = [((RPM * Tire Height) / (Rearend Ratio * Trans Ratio * MPH * 336)) -1] * 100

Do I use the the tranny gear ratio the car is in for the MPH and rpm I am using?
For example

I am at 6150rpm 1st gear 39 mph do i use the trans ratio of 2.74?

 

[bison]

To calculate converter slippage using the following formula:

Conv Slip% = [((RPM * Tire Height) / (Rearend Ratio * Trans Ratio * MPH * 336)) -1] * 100

Do I use the the tranny gear ratio the car is in for the MPH and rpm I am using?
For example

I am at 6150rpm 1st gear 39 mph do i use the trans ratio of 2.74?

Yes. You need exact tire height measurements to be accurate. Sidewall numbers are not accurate.

 

[Mad_Trbo]

tire side wall height

so measure off with straight edge and ruler to get the exact sidewall heights?

I assume air pressure may change this number!!!

 

[Mad_Trbo]

Holy smoke but no perspective

30% seems crazy.

so does this change as the mile per hour increases.

Just straight logic tells me know, it is strictly rpm.

30% without really thinking about it I don't know what this equates to for me in acceleration but it seems I am leaving quite a bit on the table

And from what I am seeing / understanding it is worse earlier on.

 

[bison]

30% seems crazy.

so does this change as the mile per hour increases.

Just straight logic tells me know, it is strictly rpm.

30% without really thinking about it I don't know what this equates to for me in acceleration but it seems I am leaving quite a bit on the table

And from what I am seeing / understanding it is worse earlier on.

Its probably correct. You have to run the car till g force drops below a practical level to get an accurate slip number. Slip is likely 50% on a ratio change even though the g force is likely very high. Wat your concerned with is if the converter is able to couple near your shift rpm. My 2-3 is at about 52-53mph and its at about 3% slip at that point. On hte 2-3 shift it drops to about 5550 and the mph is around 92-93. So 40% slip. By the time im at 142mph in 3rd its back at 3%.

 

[S2V6RACER]

Actual driveshaft speed and engine RPM is the most exact way.

You can overlay the logs (if possible) and take a look at what is going on when you turn up the power all the way down the track. Slip #'s on the big end tell only part of the story. A G meter is a very handy tool to have in the data log.