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OBDII
There is a lot of new products that plug into your OBDII (On Board Diagnostics) port and claim to measure horsepower, torque, 1/4 mile etc. We have studied the OBDII protocol and the problem is that OBDII system was designed as a diagnostic tool to be used in a mechanics shop. So things such as timing accuracy and speed of the sensor readings were not critical. But for performance measurements you need exactly those things. So when it comes to measuring performance through OBDII that is a problem. It can be done easily but it's not accurate.
For performance measurements you need acceleration. OBDII devices calculate the acceleration from speed and time. In theory there is nothing wrong with that method but the problem is resolution (how often is the speed updated?) With OBDII it's only a few times per second! So acceleration readings are "choppy" and not accurate.
The best way to get accurate acceleration is to measure it with an accelerometer. GTECH takes 4000 readings per second from each of its x,y and z precision accelerometers!
