Racepak Download

[Tom Goldman]

When using the 8 magnet driveshaft collar on cars with numerically low rear gears ,I find the driveshaft and g-meter readings are very close.
On my car with a 4.30 rear gear there is about a .009 second difference.
I'm sure gear ratio and car weight and shock settings will greatly effect the time difference, but the 8 magnet collar gives much better resolution of the driveshaft rpm.
I noticed a huge difference between my driveshaft readings at Lebanon Valley and ones on a graph recorded with 2 magnets.
Non throttle stop cars probably don't need this resolution ,but for a car running the .90 index's it's invaluable.

[Don Eckel 111]

Originally Posted by Tom Goldman

When using the 8 magnet driveshaft collar on cars with numerically low rear gears ,I find the driveshaft and g-meter readings are very close.
On my car with a 4.30 rear gear there is about a .009 second difference.
I'm sure gear ratio and car weight and shock settings will greatly effect the time difference, but the 8 magnet collar gives much better resolution of the driveshaft rpm.
I noticed a huge difference between my driveshaft readings at Lebanon Valley and ones on a graph recorded with 2 magnets.
Non throttle stop cars probably don't need this resolution ,but for a car running the .90 index's it's invaluable.

I agree 100% that with more magnets on the collar, the movement of the car should be very close with the g-meter. With 8 (45 degrees apart), there would be next to no lag in the recorder picking up the driveshaft.

[MOTORSPORTS Innovations]

All good points. To SST159 there is no way to get any of the timing system info into a data log so we use some item in the car to start the run.

Here is what I think on the subject:

- As mention above, unless you have a 8 magnet collar, I would not recommend using the DS movement for the start point.
- Yes the G-meter is my #1 recommendation for the start point.
- I sometimes use the RPM jump when TB releases because it's a bit easier (that was the reason in the vid) and it really is the mechanical beginning of the run. If the valve body, or TB solenoid, is not releasing exactly the same this is how you see it.
- It's important to remember that this is not a permanent change to the log file - you can reset the start point at a later time.
- Sometimes if I am overlaying more than two runs I will purposely offset the start in the runs so I can see overall picture better.

[SST159]

Originally Posted by Tom Goldman

When using the 8 magnet driveshaft collar on cars with numerically low rear gears ,I find the driveshaft and g-meter readings are very close.
On my car with a 4.30 rear gear there is about a .009 second difference.
I'm sure gear ratio and car weight and shock settings will greatly effect the time difference, but the 8 magnet collar gives much better resolution of the driveshaft rpm.
I noticed a huge difference between my driveshaft readings at Lebanon Valley and ones on a graph recorded with 2 magnets.
Non throttle stop cars probably don't need this resolution ,but for a car running the .90 index's it's invaluable.

Another good point.
I think for my purpose, the G meter may be sufficient to start the run.
In the mean time I should look into the availability of an eight magnet collar.
In the long run that sounds like the way to go. I cannot remember, however I believe my current collar has 4 magnets.
Thanks for the input and suggestions.