Short Answer:

The Morse test is a method used to find the indicated power and mechanical efficiency of a multi-cylinder internal combustion engine without using an indicator diagram. It is performed by running the engine under full load and then successively cutting out each cylinder to note the drop in brake power. The difference in power helps to calculate the indicated power of each cylinder.

This test is simple, practical, and commonly used in workshops and laboratories. It helps engineers determine how much power each cylinder contributes to the total engine output and also identifies problems like imbalance or low performance in any cylinder.

Detailed Explanation :

Morse Test

The Morse test is a well-known experimental method used to determine the indicated power (I.P.), brake power (B.P.), and mechanical efficiency of a multi-cylinder internal combustion engine. It was developed by the Morse Company; hence, it is named the Morse test. The main advantage of this test is that it does not require the use of an indicator diagram, making it simple and suitable for practical applications.

The Morse test is primarily conducted on multi-cylinder engines such as four-cylinder or six-cylinder engines. It helps in identifying how much power each cylinder produces and checks whether all cylinders are functioning uniformly. If one cylinder produces significantly less power, it indicates a problem such as improper fuel injection, compression loss, or poor ignition.

Purpose of Morse Test

The main objectives of performing a Morse test are:

To determine the indicated power of each cylinder in a multi-cylinder engine.
To find the mechanical efficiency of the engine.
To compare the performance of individual cylinders.
To identify faulty or underperforming cylinders.

Principle of Morse Test

The Morse test works on the principle that the total brake power of a multi-cylinder engine is equal to the sum of the brake power contributed by each cylinder. When one cylinder is cut off (made inoperative), the total brake power of the engine decreases because that cylinder no longer produces power. The reduction in brake power corresponds to the indicated power of the disabled cylinder.

The test is based on the following relationship:

The sum of the indicated power of all cylinders gives the total indicated power of the engine. Once the total indicated power and total brake power are known, the mechanical efficiency of the engine can be calculated as:

Procedure of Morse Test

The engine is first started and allowed to reach its normal operating temperature.
The engine is then run at a constant speed and load condition.
The total brake power of the engine is measured using a dynamometer when all cylinders are working.
Next, one cylinder is cut off (for example, by short-circuiting the spark plug or stopping fuel supply to that cylinder).
The reduced brake power is again measured.
The difference between the total brake power and reduced brake power gives the indicated power of the cylinder that was cut off.
The process is repeated for each cylinder one by one, and the indicated power for all cylinders is calculated.
Finally, total indicated power, brake power, and mechanical efficiency are determined.

Example Calculation

Suppose a four-cylinder engine develops a total brake power of 40 kW with all cylinders working. When each cylinder is cut off one at a time, the measured brake powers are as follows:

Cylinder 1 cut off: 30 kW
Cylinder 2 cut off: 31 kW
Cylinder 3 cut off: 29 kW
Cylinder 4 cut off: 30.5 kW

Now,
I.P. of Cylinder 1 = 40 − 30 = 10 kW
I.P. of Cylinder 2 = 40 − 31 = 9 kW
I.P. of Cylinder 3 = 40 − 29 = 11 kW
I.P. of Cylinder 4 = 40 − 30.5 = 9.5 kW

Total I.P. = 10 + 9 + 11 + 9.5 = 39.5 kW

Mechanical Efficiency = (40 / 39.5) × 100 ≈ 101% (This may slightly vary due to rounding or measurement error).

Advantages of Morse Test

It is simple and easy to perform.
No need for complex indicator diagrams or special instruments.
Helps identify weak or faulty cylinders.
Useful for calculating mechanical efficiency quickly.
Can be performed using standard testing equipment.

Limitations of Morse Test

It is only applicable to multi-cylinder engines.
The test assumes that engine speed remains constant, which is not always true.
It cannot be used accurately for single-cylinder engines.
The results may be slightly inaccurate due to speed variations or heat loss.
Not suitable for engines with automatic electronic control systems where cylinders cannot be easily cut off.

Applications of Morse Test

Used in engine testing laboratories to study engine performance.
Helpful in research and development of multi-cylinder engines.
Used in workshops for maintenance and fault detection.
Helps in checking uniformity of power distribution among cylinders.
Commonly performed in automobile and marine engine testing.

Conclusion

The Morse test is a practical and simple method for determining the indicated power and mechanical efficiency of multi-cylinder engines. It helps in comparing the performance of individual cylinders and detecting problems such as poor combustion or low compression. Although it has some limitations related to speed variation and applicability, it remains one of the most convenient methods for evaluating engine performance in workshops and testing centers.