Morse Test Rig — IC Engine Virtual Lab

The Morse Test Rig Virtual Lab simulates the classical experiment for determining the indicated power (IP), friction power (FP), and mechanical efficiency of a multi-cylinder spark-ignition or compression-ignition engine. Devised by H. Lloyd Morse, the test is the standard textbook method for measuring IP of multi-cylinder engines without using a complex indicator diagram. Choose from four engine presets (3-cyl diesel, 4-cyl petrol, 4-cyl diesel, 6-cyl petrol), set the test speed and dynamometer arm length, and run the cut-out sequence to compute each cylinder's IP, the total IP, friction power, and mechanical efficiency.

An SI / Imperial unit toggle instantly switches power (kW ↔ hp), torque (N·m ↔ ft·lbf), arm length (mm ↔ in), and brake load (kg ↔ lb) throughout the rig. Live readout badges show speed, load, BP and phase. After the test, export readings as CSV or save the bar chart as PNG with watermark.

The left canvas shows the multi-cylinder engine with animated pistons, spark/injection events and a rotating crankshaft coupled to the brake dynamometer. The right canvas shows a real-time bar chart of brake power for each cut-out condition and the calculated indicated power per cylinder. Below the canvas are the cylinder cut-out toggle buttons — one per cylinder. Click any cylinder to short-circuit its spark plug (or cut its fuel) and watch the bar chart and readouts update.

To run a complete Morse test: (1) Pick an engine preset. (2) Set the speed N and arm length L. (3) Click Start Engine. (4) With all cylinders firing, click Record BP to log the total brake power. (5) Cut out cylinder 1 (click its button) — the brake load is auto-adjusted to hold the same speed — then click Record BP. (6) Restore cylinder 1 and repeat for each remaining cylinder. (7) The total IP, FP and mechanical efficiency are computed automatically once all cylinders have been measured.

The engine canvas animates pistons rising and falling in firing order (1-3-4-2 for a 4-cylinder inline, 1-5-3-6-2-4 for a 6-cylinder). Firing cylinders show an orange flame in the combustion chamber and a yellow spark; cut-out cylinders are dimmed with a red "OFF" overlay. The crankshaft rotates at the chosen RPM and drives the brake drum on the right of the canvas. The spring balance under the dynamometer arm shows the current brake load, which the simulator auto-adjusts to keep speed constant when a cylinder is cut out.

The bar chart canvas plots the brake power for each test condition (All cyl, −Cyl 1, −Cyl 2, ...) and the indicated power of each individual cylinder once all measurements are complete. Annotated markers show the total IP, FP and η_mech. Right-click either canvas for a context menu (Save Image, Copy Readings, Reset Test).

Explore mode presents an illustrated reference library on the Morse test, organized into four categories: Basics (definition, purpose, historical background, applicability), Procedure (the complete step-by-step laboratory method), Formulas (BP, IP, FP and η_mech with full worked examples in both SI and Imperial), and Limitations (key assumptions, sources of error, why the test works only at constant speed).

Each card includes the engineering background, equations, and a worked numerical example using realistic engine data. Use Explore mode to revise before exams or before attempting Practice and Quiz modes.

Practice mode generates random Morse-test numerical problems: given the brake load and arm length, compute the brake torque and brake power; given BP and BP_i for each cylinder, compute IP, FP and η_mech. Type your answer, click Check, and use Show Solution for a step-by-step walkthrough.

Quiz mode tests both conceptual knowledge and numerical skill with five multiple-choice questions per session. After the fifth question you receive a score with star rating and the option to take a new quiz. The badges and live readouts are hidden in Practice and Quiz to prevent giving away answers.

The simulator combines the Morse test with continuous fuel measurement (animated fuel burette on the left of the engine canvas) so it can compute the full set of IC-engine performance metrics, not just mechanical efficiency. Each engine preset has a realistic calorific value (44,000 kJ/kg for petrol, 42,500 kJ/kg for diesel) and a baseline BSFC (220–285 g/kWh).

• Mechanical efficiency η_mech = BP / IP — from Morse cylinder cut-out. Typical 75–92%.
• Brake thermal efficiency η_bth = BP × 3600 / (m_f × CV) — fraction of fuel energy reaching the shaft. Typical 25–32% petrol, 35–42% diesel.
• Indicated thermal efficiency η_ith = IP × 3600 / (m_f × CV) — combustion + gas cycle only. Always > η_bth.
• BSFC = m_f / BP (g/kWh) — practical fuel economy metric. Lower is better.
• ISFC = m_f / IP (g/kWh) — same as BSFC but per indicated power.

Key relationship: η_bth = η_ith × η_mech. The Morse test by itself only gives η_mech; the thermal efficiencies require knowing the fuel consumption rate, which a real lab gets from a graduated burette and stopwatch and this simulator computes from the simulated BSFC curve.

The instrument cluster shows FUEL RATE (g/h) and η BRAKE TH. (%) live. After a complete Morse run, the result cards add BSFC, η Brake Thermal, and η Ind. Thermal, and the exported CSV includes the full performance summary.

Click the SI / Imperial toggle in the top-right of the controls bar to switch between unit systems. In SI mode, brake load is shown in kilograms (kg), arm length in millimetres (mm), torque in newton-metres (N·m), and power in kilowatts (kW). In Imperial mode, load is in pounds (lb), arm length in inches (in), torque in pound-feet (ft·lbf), and power in horsepower (hp). All readouts, slider labels, badges, result cards and the exported CSV update instantly to the active unit system; internal calculations are always carried out in SI.

• Always record the total brake power before cutting out any cylinder — this is the reference value BP that all other measurements are compared against.
• Restore each cylinder before cutting out the next. The Morse test isolates one cylinder at a time; cutting two simultaneously breaks the constant-FP assumption.
• The friction power FP must be the same whether all cylinders fire or only (n−1) do. This requires speed to remain constant — the simulator automatically adjusts the brake load to enforce this, just as a real lab operator does with the dynamometer hand-wheel.
• In a real lab, allow about 30 seconds for the engine to stabilise after each cut-out before reading the dynamometer — transient torque pulses settle out only at steady state.
• For a 4-cylinder engine, expect each cylinder to contribute roughly the same IP if combustion and compression are healthy. A cylinder with noticeably lower IP indicates a problem (worn rings, faulty injector, weak spark).
• Switch to Imperial units to see how US automotive specifications quote horsepower and torque — useful when reading SAE engine test reports.
• Export the test data as CSV after a run and open it in Excel to plot BP vs cylinders firing — the slope of the line is the average IP per cylinder.