My project is the design of a data logger and to calibrate numerous sensors to it. One thing that I wish to log is the angle of tilt on a racing car. The idea that I had was to attach two accelerometers, one sensing the one way with the other inverted 180degrees in each axis. Am I right in thinking that I can subtract the differences from the 2 acceleromteres to allow me to measure the angle of tilt on the vehicle, or is there another way of doing this?
No, if they are 180° apart, they cancel each other out, and if you then subtract them, you will get double the value.
And, if you want to measure the tilt while the car is accelerating, I don't think this is going to work at all. You have a variable acceleration of the car, and a variable tilt to the fixed acceleration of gravity. That leaves you with floating data.
Yes, you need a Gyro with at least 2 axis to measure the tilt front and back and to measure tilt side to side. A third gyro to measure yaw isn't necessary, but would complete the package and give you data on lateral slides. The tilt measured by the gyros would be used to correct the measurement of the accelerometer. You'd need a full 3 axis accelerometer to measure all the turning forces and correct for tilt of the car.