[Jackpine]

Originally Posted by 88Racing

That's approximately the place holder for the TS on my gryphon also. And yes that "rounding up 3mm is weird also but maybe its upping it to an inch scale value that we don't get to see?

I thought maybe that was the case too, but since there are EXACTLY 25.4 mm in an inch, I checked both values. 2481 is 97.677... inches and 2484 is 97.795... inches. Neither one is a simple whole number.

But, here's a thought: 2481 works out to 648.667 revs/mile. 2484 is 647.884 revs. Now, if the figure actually needed for the PCM was revs/mile, it MAY be using 648, which works out to a TS of 2483.555.... (which "rounds" to 2484). So, I think the software in the Gryphon is calculating revs/mile from the TS and then "truncating" it (dropping the decimal result) and using 648. In reloading previous settings, it calculates TS as 2483.5556, which it "rounds" to 2484.

And here's where it gets interesting: If you leave 2484 in for TS, the next rev/mile result is 647.88, which truncates to 647. Reloading again, the TS becomes 2487.394 which rounds to 2487 (another increase of 3 mm). And, I remember this happening, way back when I left the 2484 value in. From now on though, nothing should change, because the new revs/mile is 647.103 which truncates to 647 again.

In my case, the accumulated error is only 0.2% (12.8 feet/mile), or almost 1 mile every 400 miles. Obviously not enough to worry about. Different TS values might take longer to "stabilize" though and there could be a larger accumulative error. If I'm right about "truncating" and "rounding", it would be better to "truncate" all the time, I think. (I would stabilize at 2483 in that case).

I know this has bored most everyone to death, so I apologize. But knowing these things helps me put out meaningful advice to the "new" people. And, I know other programmers ask for revs/mile, not tire circumference. Wonder why the Gryphon/Edge chose circumference?

- Jack