Torque and power are only proportional at the same point in the rev range. For any given engine, the quoted torque and power outputs are peak values, ie the highest torque value and the highest power value regardless of RPM.
I have annotated a dyno graph of a 1.7 CRDi below, just as an example.
The blue solid line is the torque curve with the Bluespark box fitted, the blue dashed line is the power curve with the Bluespark box fitted.
The red solid and dashed lines are stock torque and power respectively.
The green circle highlights the point of peak power, and the orange circle highlights the point of peak torque:
I could (if I wished) make a file that would give identical gains to the above prior to 2500RPM, tailing off to zero gains (matching back to the red lines) by 3000RPM. That would give the same peak torque gain and zero peak power gain.
Conversely I could make a file that was exactly as the stock (red dotted) plot is, with a gradual increase from 3000RPM up to 4000RPM continuing on to the same power shown in the green circle. That would give zero peak torque gain, but an identical peak power gain.
Torque can be (and often is) limited to help limit wear on clutches and gearbox components, reduce wheelspin and improve general tractability.
Real world extreme examples of torque and power not matching are comparisons of trucks and supercars:
- An Audi R8 5.2 V10 FSI makes 525hp, but only 530Nm.
- A 13 Litre Scania truck makes only 450hp but a massive 2350Nm torque.
The Audi V10 is designed to make peak power screaming round to 8000RPM, whereas the Scania is designed to pull a 40 ton trailer at less than the Audi's idle speed.
Hopefully this helps a bit.
Best regards,
Edd
