View Single Post
Old 09-07-2008, 03:32 AM   #13 (permalink)
needs more cowbell
dcb's Avatar
Join Date: Feb 2008
Posts: 5,038

pimp mobile - '81 suzuki gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Volkswagen Golf TDI
90 day: 53.56 mpg (US)
Thanks: 158
Thanked 267 Times in 210 Posts
Collecting data for a half second is entirely appropriate for display purposes, because that happens to be the display refresh rate. I have not suggested anything that would interfere with the accuracy of the trip accumulators, those are more important than the instant display. And yes, you need a "slop factor", as mentioned, my metro looks like 1.6.

re: traces, Here are a couple pulses (pm'd you the link):

The problem comes in when you want to do something like an accurate coast down test to determine your cda/crr. cda/crr doesn't exist yet, but 1/2 a second resolution is less than ideal for that task, more than one pulse is also less than ideal too, the signal on the metro itself is far from ideal, there's only so much you can do with it.

The nice thing about the "slop theory" and tracking the min and/or max vss pulses per 1/2 second in the interrupt handler is that it is based on a physical limit of the existing system, i.e. the min or max should be mostly those readings where most/all the slop was at it's maximum extents, and thus we have a reference point, sort of
  Reply With Quote