90 degree bank turns are a bit steep for first timers!!! You cant maintain a constant bank angle, there is no vertical lift component. Sounds like a bit of a cowboy instructor you got there. Be wary!!!
Next time he pulls a stunt like that, raise the nose and put in as much rudder in the direction of the turn as you can. Sounds like you were in a sprial dive when the 172 was at 160 kts???
