I have a Nissan Fuga (Infinity M45 in the USA) tuned with UpRev, and have changed the final drive gears which has resulted in some complaints from the ECU, and has disabled cruise control. The ecu error is saying it is receiving miss matched speed data from the transmission and the speed sensors on the wheels. Thats cool and makes perfect sense.
Where I am stuck is there are tables for the final drive ratio in the ECU that can be changed via UpRev. But I don't know how they work becasue the numbers in them make no sense. EG, the stock ratio is 3.13 to 1, and the table value is 0.393479. I looked at another rom example from a G35 with 3.357 gears and it had a value of 0.352707 in the table.
There are also tables for wheel radius and tire effective radius, so I thought maybe the value was related to how far the wheel rolls per drive shaft revolution. But using the default values of these I get a value of 0.36575, not 0.393479. So I am unsure if that is how this is worked out.
Does anyone have any ideas or know how these tables work to give the ECU correct data on the final drive ratio?