(a) Importance of Cylinder Power Balance

For the economical and efficient operation of a multi-cylinder engine, each cylinder should develop approximately equal power at all operating loads. This condition is known as a balanced engine, and minor adjustments may be required to achieve and maintain this balance.

If the engine operates with unequal cylinder power, the following harmful effects may occur:

• Overloading of bearings and running gear, which may lead to bearing or gear failure.
• Overloading of one or more cylinders, resulting in piston blow-by, overheating, or piston seizure.
• Excessive engine vibrations, which create fluctuating stresses during prolonged operation and can lead to fatigue failures.

Possible consequences of fatigue include:

• Cracking of bearing metals.
• Fracture of studs or bolts.
• Cracking of the crankshaft.
• Slackening or failure of holding-down bolts.

(b) Method for Assessing Cylinder Power – Indicator Cards

One of the most common methods of assessing cylinder power is by using indicator cards (also known as power cards or out-of-phase cards).

In modern electronically controlled engines, pressure transducers fitted to the indicator cocks measure cylinder pressure electronically. The recorded data is processed and displayed through the Engine Control Room (ECR) computer system.

Procedure:

1. Run the engine at approximately 85% of the Maximum Continuous Rating (MCR).
2. Open the indicator cock and blow through it to remove any carbon deposits or moisture.
3. Connect the mechanical or electronic indicator to the indicator cock and open the cock.
4. Record the out-of-phase indicator diagram, which is stored in the indicator or electronic measuring device.
5. Remove the measuring device and repeat the same procedure for each remaining cylinder.
6. Transfer the recorded data to the computer and compare the results for all cylinders.
7. Compare important parameters such as:
   • Compression pressure.
   • Peak firing pressure.
   • Indicator diagrams between cylinders.

(c) Methods of Achieving Cylinder Power Balance

The power developed by a cylinder depends on several factors, including:

• Air supply.
• Quantity of fuel injected.
• Fuel injection timing.
• Fuel atomisation.
• Scavenge air temperature.
• Proper mixing of air and fuel.

Cylinder power balance is achieved by checking and adjusting these parameters as follows:

1. Fuel Injection Adjustment

• If the peak firing pressure is low, increase the fuel delivery by adding shims to the fuel pump.
• If the peak firing pressure is high, reduce the fuel delivery by removing shims from the fuel pump.

2. Fuel Atomisation

• Ensure the fuel injector produces proper atomisation within the manufacturer's specified limits.
• If atomisation is poor, replace the fuel injector nozzle.
• Verify that the injector opening and closing pressures comply with the maker's specifications.

3. Compression Pressure

• Low compression pressure may result from blow-by past the piston rings or leakage through the exhaust valve.
• Inspect these components and overhaul or replace them if necessary to restore proper compression.