why does torque increase with bhp?

Torque drops do to several reasons. The intake and exhaust systems are resonance chambers and as such have natural frequencies at which they actually act as a boost system on the intake side and scavenge exhaust on the opposite side.

Then there is the fact that horse power is applied torque. Torque is potential horsepower and once the optimum engine operation point is reached, then torque has to decrease as this potential is used as horse power.

a million. the dating is that BHP will strengthen with torque. power is proportional to the fabricated from torque cases rpm, so increasing torque 10% at any particular rpm will strengthen BHP 10% on an identical rpm. All power ameliorations at any rpm are the direct results of torque ameliorations. 2. for an identical reason, torque continuously has to drop off purely before the flexibility curve. All factors farther precise of the curve have bigger rpm (that's what the X axis is); in case you had - to illustrate - consistent torque, the flexibility could be a at once line transforming into gradually as rpm bigger. because it is, factors interior the engine (quite often valve themes) shrink the engine velocity and reason the torque to drop at bigger rpm. This produces a torque height with a power height happening later whilst the extra rpm no longer compensates for the decreased torque.