i have the speedo set at 12% and im still fiddeling with it, 12% isnt perfect, i just need to gps it or use milemarkers....i think 13-13.5 is more like it, i know it seems more than it should but at 11, and 11.50 on the freeway it was still off by a noticable margin.

 

Dialing in the correction factor by the calculated error for your gears should get you to within about 2% to 3%, which is what the error was before you changed the car. If you are still seeing that kind of error (21%), perhaps you should double check the Yellow Box wiring. You may have it hooked up wrong.

 

no no no, the 21% error is with 0 correction, all switches set to 0, it just kinda surprised me that it was that much

i'll do the mile marker calibration tonight and post the results

 

I had to set my Yellow Jacet to 24 to get the speed right. Luckly I had a GPS to help me, then a friend driving next to me to confirm it.
I started with 11 then went up from there.
I have 4.57's and 18 inch wheels, running 255 35's.

aquatic

 

OOOOoooOOO

 

ok, i did the mile marker calibration and i tried to do it to the 0.01 mile so i measured the seconds @36mph when i passed a mile marker, here's what i got

1---> 5 miles and reading of 5.6 at the marker + 5seconds when the tripmeter clocked 5.7 miles

2---> 10 miles and reading of 11.3 at the marker + 9seconds when the tripmeter clocked 11.4 miles

so here's the calculations i did

1---> (5.7 - 0.05) / 5.0 = 1.130
2---> (11.4 - 0.09) / 10.0 = 1.131 pretty accurate if you ask me

(1.130 + 1.131) / 2 = 1.1305 ~ 1.1300 which is a correction of 13.00%


according to my logic i did the right calculation by subtracting the seconds from the reading after i passed the marker, it should NOT be added, please, correct me if im wrong?

if it was added the correction would then be 15.00%, but im pretty positive that i did everyting right so i have my yellow box set @ 13.00% as of now and i will hook it up in 15 minutes so if i did someting wrong, let me know ASAP, thx

 

I think your calculations are correct and 13% sounds reasonable to correct for the gears and the existing speedo error of this car. Therefore, these numbers seems to be in vast contrast to what you reported in your first post. I'm wondering if the policeman was dicking you around.

 

1.1305 is rounded to 1.131

 

there is no correction factor on the table for 1.131, that's why it's 1.1300

 

As a side note, you can easily check your precise speed with almost any GPS nav unit, if you know somebody who has one. Flat ground gives the best results, of course.