So what's the black magic to adjusting the speed for a larger tire. Currently reading 12% slower than actual. I've tried adjusting the final drive ratio, the tire rev/mile and when you touch the output calibration the speedo pegs at 180 mph as soon as the car moves. The only way to fix it is to reload the base file into the ECU.
2006CTSVspeedo.jpg
In the menu go to Edit and use the Gear/Tire wizard. Make sure Make sure both check mark boxes are checked.
There are certain applications that the Tire/Gear Ratio Wizard just doesn't work on. This is one of them.
I'll be glad to help.
What was the original gear ratio and tire size? What is the new gear ratio and tire size?
OK i'll bite. What ones have the problems? What is the cure if I run into them?Originally Posted by kevin87turbot
Off top of my head, all of the 98 black box ECU's, some of the 2007 Tahoes/Yukons/Suburbans, and apparently the 2006 Cadillac CTS has this oddity.2007tahoe53Lbeigestock.hpt
Check out this 07 Tahoe file and look at the Wizard. The values are pretty odd.
I just wrote a spreadsheet to calculate the VSS Tire revs/mile and the OSS PPM output, and just don't use the Wizard on these applications.
Last edited by kevin87turbot; 08-08-2021 at 09:02 AM.
I'll check out the file tonight, thanks and I may have questions later if that is ok
Wayne,
I also have an '06 V and struggled with this as the obvious usual calculators do nothing for our car. Adjustment is made by the pulses per mile box under PCM output calibration. To increase the displayed vehicle speed, lower the amount by the percentage you want it raised.
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