I know the ECU doesn't send the speed signal to the gauge cluster but I was wondering if you change then diff gear ratio will you have to adjust flashpro? I have 3.90 gear in the diff and I was wondering what and where you would adjust in flashpro for the change? Also by how much?

 

You don't really need to adjust the speed that the ECU sees, but you can adjust it using the FlashPro in the Sensors -> Speed Adjustment field. If you have 3.9 gears, then I believe you would enter 5%

 

I guess I would just have a friend watch the laptop as I go at a steady speed and compare it to my GPS?

 

You don't really need a friend. Just put the car in reverse, get up to about 40 MPH, and set the cruise control. Then hit the datalog button while cruising (in reverse of course), and take note of your GPS speed. Then stop the datalog, floor it, spin the wheel to the left, and enjoy a nice reverse switchover. Then go back home to compare the datalog speed with your GPS speed, and adjust the calibration.

 

lol what?

 

Just set the cruise control on the highway, take note of the GPS speed, turn on datalogging for a few seconds, then go home and adjust the speed based on the difference between the datalog and GPS speed.

 

I saw that and the first thing that came to mind was Reverse Vtec!!!

 

O.O This was my reaction as well...