Enter engine and curve inputs
Example data table
| RPM | Torque (Nm) | Power (HP) | Power (kW) | BMEP (kPa) |
|---|---|---|---|---|
| 1,000 | 188.0 | 26.4 | 19.7 | 1,181.2 |
| 2,500 | 274.0 | 96.1 | 71.7 | 1,721.6 |
| 3,800 | 320.0 | 170.7 | 127.3 | 2,010.6 |
| 5,500 | 273.0 | 210.6 | 157.1 | 1,715.3 |
| 7,000 | 218.0 | 213.9 | 159.6 | 1,369.7 |
Formula used
Torque from power
Torque (Nm) = 9549.2966 × Power (kW) ÷ RPM
Torque (lb-ft) = 5252 × Power (HP) ÷ RPM
These formulas convert the stated power point into a torque anchor at the chosen peak power RPM.
Power from torque
Power (kW) = Torque (Nm) × RPM ÷ 9549.2966
Power (HP) = Torque (Nm) × RPM ÷ 7127
Every RPM point uses the estimated torque value to calculate matching power in both units.
Wheel torque
Wheel Torque = Engine Torque × (1 - Drivetrain Loss ÷ 100)
This estimates usable torque after losses through clutch, gearbox, differential, and related driveline components.
BMEP
BMEP (kPa) = (4 × π × Torque) ÷ Displacement
Displacement is converted to cubic meters internally, producing brake mean effective pressure in kilopascals.
Curve construction method
The calculator builds a piecewise torque curve using four anchor points: idle torque, peak torque, torque at peak power RPM, and redline torque. A shape factor biases how quickly torque rises or falls between those anchors for smoother engineering estimates.
How to use this calculator
- Enter idle RPM, peak torque, peak torque RPM, peak power, and peak power RPM.
- Set maximum RPM and the RPM step to control the number of result points.
- Adjust idle and redline torque factors to reflect expected low-speed and high-speed behavior.
- Use the curve shape factor to make the rise and fall smoother or sharper.
- Input drivetrain loss and displacement to estimate wheel torque and BMEP.
- Choose the displayed torque unit, then submit the form to generate the full torque curve.
- Review the metrics, chart, and RPM table above the form.
- Export the finished results with the CSV or PDF buttons.
FAQs
1. What does this calculator estimate?
It estimates engine torque across the RPM range using your torque peak, power peak, idle behavior, redline behavior, and drivetrain loss assumptions.
2. Why are peak torque and peak power both required?
Peak torque shapes the midrange, while peak power defines how much torque remains at higher RPM. Using both anchors makes the curve more realistic.
3. What does the curve shape factor change?
It controls how fast torque approaches or leaves each anchor point. Larger values usually create a slower early change and stronger late transition.
4. What is the 90% usable band?
It shows the RPM range where estimated torque stays at or above 90% of peak torque. A wider band usually means better flexibility.
5. What is BMEP used for?
BMEP compares torque-producing efficiency across engines of different sizes. Higher values usually indicate stronger cylinder pressure utilization for the same displacement.
6. Does wheel torque equal real road torque?
Not exactly. It is a simplified estimate after driveline loss. Tire radius, gear ratio, and traction limits still affect real tractive force.
7. Can I use this for electric motors?
Yes, but adjust the shape assumptions carefully. Many motors hold near-constant torque first, then enter a power-limited region at higher speed.
8. Why might my inputs trigger a warning?
A warning appears when your power and torque peaks imply an unusual relationship. The calculator still runs, but the entered specifications may conflict.