Dinan Tune for X5
Unless you have the engine on a stand to measure the HP, every other method of measuring HP and torque has some serious limitations.
Yes Density Altitude, wind and grip will impact MPH. In our case, grip should be a near non issue. I have not heard of tuned X5Ms losing traction on a regular basis. You can correct for wind and DA if you really want to.
With strap on dynos, there are the different readings, on inertia dynos vs eddy current dynos. These differences can approach 10%. On all dynos, there are also the questions of strapping technique, hood up or down, how big a fan is being used, the quality of the data in the weather station, tire pressure, etc, etc.
I described the MPH method as "fun and fairly accurate". I stand by that description. I also warned about set up and weather "(This is best done where the temp and humidity are similar and the vehicle is set up the same way, i.e. tire pressure, full tank of gas, same octane gas, etc.)"
The Dinan tunes should definitely be good enough to add a few MPH on a consistent basis. You will definitely see a change in MPH with a 50 HP increase.
I stand by the formula. It is a fairly accurate way to measure HP and torque.
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