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Reply to "MTH Engine Gear Ratios"

stan2004 posted:
SanDiegoMark posted:
stan2004 posted:

Perhaps another way to look at it is to observe that 46.5 x 11 = 511.5.  That is suspiciously close to "exactly" 512.000 - in other words is a 9-bit binary shift which is arguably what you'd expect a presumably fixed-point microcontroller processor to do to represent two levels of resolution or scaling of the same underlying value.


Stan, you may be onto something here. The 46.5 number I use was derived by working backwards. With a little more 'tuning', it really could be 46.545454 and then 46.545454 * 11 = 512.

X is the same raw_value (tach stripe count).  Different slopes and different offsets but with a fixed-ratio (512) between m1 and m2. 



I can easily test this part.

I took the DTO and DOD raw values, ran the engine for about 1.5 Smiles and took the raw values again:



The DTO difference is (almost) exactly 512 times the DOD difference. Its off by just a little which could be the result of how the engine accumulates the tach counts.

So you have added another piece of the puzzle.

Last edited by SanDiegoMark
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