PaulS:
An accelerometer measures the instantaneous rate of change of velocity, along some axis. It is extremely unlikely that you can apply a change of velocity to the accelerometer in such a way that it affects only one axis.
Considering the answer of DrDiettrich , you still think that can"t be possible ? Even if it not possible with it what woud you sugget, I thought about piezo sensor in 4 sides in the car and then get the highest value to determinate what angle it come from.
DrDiettrich:
Knock at the sensor from different angles, and try to find a relationship between angle and accelerations. Two accelerations (X and Y) are required for the determination of an angle, so you have to deal with two values anyhow. Eventually the sensor chip is not aligned properly, causing a shift of the axes?
Well , I already tried the chip without any hit on the car and I got nothing so I think it's quite good calibrated. By the way, to clarify, I don't need an precise angle. I just need 90 180 270 or 360 /0 . Have you already worked with this kind of chip ?
Anyway, already thanks to you two, I'm getting further in this !