S11EPS is correct, it's mainly down to the gearing of the car (plus the extra weight of the engine itself)
Torque is the measure of the turning force of the engine, and is therefore directly correlated to the acceleration of the car by simple Newtonian physics:
Acceleration = Force / Mass, i.e. more force, more acceleration
BHP is the power of an engine, which is the rate at which work is done so it follows that BHP, rather than indicating how quick the acceleration is, it is actually a better indicator of the ultimate speed the car can achieve in any given gear.