Last night, I did my first software update of the Speedo cluster since it has been in the car.
It was a tiny bit stressful as the programmer I use also erases the boot code in the PIC (uProcessor) so there is a window of time where if something goes wrong, or if I make a mistake, the speedo is "bricked". That would require having to pull the whole lot out to be able to get at the emulator connector on the circuit board inside the speedo housing - lots of work. (I bricked the speedo a number of times during it's software development so it's not beyond me to "get it wrong".) It all went well.
The update came about following the speedometer inaccuracy mentioned a couple of posts ago. Woody from the AEVA forums sent me this extra gem of information about tyres.
http://www.carbibles.com/tyre_bible_pg4.html#slr
Another website I found also supported this although it results in slightly different figures.
TRC Calculator
(Link fixed)
The combination of different differential ratio and the 0.96 rolling curcumference correction (from the above articles) completely explains the 67km/h vs 60km/h error - although I'm still perplexed at why anyone would have changed the diff in the first place.
So I have altered the ODO and Trip meter calculations to use the 0.96 compensation but left the speed calculation about 3% high - just by not applying this compensation. It also appears (from the second web link) that the static and dynamic rolling curcumference can change. It moves back to about 0.97 at 60km/h and probably changes more at higher speed - getting closer to calculated value. This of course depends on initial tyre inflation. I don't think I'll go that far but I will measure the static circumference of the Hancook Enfren LRR tyres when I get them using a driveway/chalk rolling test.
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment