Choose a method, enter the engine data, and submit the form. Detailed torque, power, gearing, or BMEP results will appear here.
Enter one operating point per line using RPM, power. The analyzer calculates torque, finds peak values, and creates a chart.
| RPM | Power input | Power (kW) | Torque (N·m) | Torque (lb-ft) |
|---|
Compare torque, power density, and torque density for two engines at selected operating points.
Engine A
Engine B
Formula used
| Calculation | Formula | Typical use |
|---|---|---|
| Torque from kilowatts | T = 9550 × kW ÷ RPM | Find crankshaft torque from a rated power point. |
| Power from torque | kW = T × RPM ÷ 9550 | Estimate output at a measured torque and speed. |
| Four-stroke BMEP torque | T = BMEP × Vd ÷ 4π | Compare engine loading independently of displacement. |
| Two-stroke BMEP torque | T = BMEP × Vd ÷ 2π | Account for one power cycle per crank revolution. |
| Mechanical torque | T = F × r × sin θ | Calculate turning moment from force geometry. |
| Wheel torque | Twheel = Tengine × gear × final drive × converter × efficiency | Estimate axle torque after drivetrain multiplication. |
How to use this calculator
- Select the calculation method matching the information you already know.
- Enter engine values and choose the correct units beside each field.
- Review efficiency, gearing, engine-cycle, and pressure assumptions carefully.
- Select Calculate to view the result, conversions, formula, and substituted values.
- Use the copy, print, CSV, or PDF controls to save the result.
- For a torque curve, paste several RPM and power pairs into the analyzer.
Understanding diesel engine torque
Diesel torque describes the crankshaft turning force available at a specific engine speed. It is especially important for towing, hauling, acceleration, and operating machinery under load. A high torque value at low RPM usually provides strong pulling performance.
Horsepower and torque are directly related through engine speed. Torque can be high while power remains moderate when the crankshaft turns slowly. As RPM increases, the same torque produces more power because work is completed faster.
Torque versus horsepower
Torque measures rotational force, while horsepower measures the rate of doing work. Diesel engines often produce peak torque before reaching peak power. This difference explains why an engine can feel strongest before its highest horsepower speed.
Brake mean effective pressure
BMEP is a normalized indicator of engine loading and torque production. It allows engines with different displacements to be compared on a similar basis. Higher BMEP generally indicates more torque generated from each unit of displacement.
Crankshaft and wheel torque
Crankshaft torque is measured before gearbox and final-drive multiplication. Wheel torque is usually much larger in lower gears because the ratios multiply the available turning force. Drivetrain losses reduce the theoretical value before it reaches the tires.
Boost and efficiency assumptions
Turbocharging increases intake manifold pressure and potential air mass. Real torque also depends on fuel delivery, combustion quality, intercooling, exhaust restriction, and electronic controls. The boost mode is therefore best used for comparisons, not certification.
Using a torque curve
A single operating point cannot show how an engine behaves across its working range. Multiple RPM and power values reveal peak torque, peak power, and average output. This information helps compare engines, gears, and expected load response.
Example calculations
| Power | RPM | Calculated torque | Typical interpretation |
|---|---|---|---|
| 75 kW | 2,000 | 358.13 N·m | Compact diesel operating near peak torque. |
| 100 kW | 2,500 | 382.00 N·m | Medium-duty output at a higher speed. |
| 150 hp | 1,800 | 437.67 lb-ft | Strong low-speed pulling torque. |
| 200 kW | 3,000 | 636.67 N·m | Higher-output diesel performance point. |
Frequently asked questions
What is a good torque value for a diesel engine?
A good value depends on displacement, vehicle mass, gearing, and intended duty. Compare torque per liter and the RPM where peak torque occurs.
Why do diesel engines make strong low-RPM torque?
High compression, long stroke geometry, turbocharging, and combustion calibration often support strong cylinder pressure at lower engine speeds.
Is horsepower more important than torque?
Neither is universally more important. Torque affects turning force, while power shows how quickly work can be delivered across speed.
What does the constant 9550 mean?
It combines angular-speed and unit conversions when power is entered in kilowatts, torque in newton-meters, and speed in RPM.
Can this calculator estimate wheel torque?
Yes. Enter crank torque, gearbox ratio, final drive, efficiency, converter factor, and tire diameter for an engineering estimate.
Why is measured wheel torque lower than theoretical torque?
Bearings, gears, fluid drag, tire deformation, converter slip, and measurement conditions create losses not captured by ideal multiplication.
What is torque per liter?
Torque per liter divides engine torque by displacement. It helps compare how effectively differently sized engines produce rotational force.
Can BMEP be calculated from torque?
Yes, by rearranging the BMEP torque formula. This page currently focuses on torque output from a known BMEP and displacement.
Does turbo boost increase torque proportionally?
Not always. Air temperature, compressor efficiency, fueling, smoke limits, injection timing, and engine protection strategies affect the final result.
Are these results suitable for engine certification?
No. Use calibrated dynamometer testing and manufacturer procedures for certified performance, compliance, warranty, or safety-critical decisions.