[ODE] Calculating G force

[Anders Olofsson]

How would I calculate the G force that a body is subjected to?. G force as 
in when a fighterjet turns or a F1 car makes a sharp turn..

I was thinking something like this:
Force=(velocity1-velocity2) / time between velocity measurement.

But I need it to be in the bodys coordinatesystem, mainly in its upward 
(jet) or sideway (car) direction. Take the bodys velocity and use 
dBodyVectorFromWorld and then do the force calculating, will do the trick?

I guess I manually have to add the earth gravity part somehow since if the 
bodys velocity is zero it still should have 1 G downwards..

--Anders