This discussion covers basic knowledge, not a magical one-step solution. However, if you truly internalize this, it can bring significant practical benefits. Unfortunately, technical discussions in many forums are fading, and most posts are just: “My machine broke, what should I do?”

1. Purpose of Engine Power Testing

To evaluate and judge the performance of the internal combustion engines in operational construction machinery, it is sometimes necessary to perform power testing. This helps determine:

• Excessive stalling (commonly called “engine choking”),

• Possible insufficient engine power.

Because operational construction machinery has many variable conditions and uncertainties, and due to the complexity and cost of sensors and test instruments, no reliable online power-testing method for in-service construction machinery engines has been widely implemented.

2. Historical Context

In the 1980s, the engine industry experimented with no-load engine dynamometer testing, where the engine’s rotational acceleration and inertia of its rotating components were used to estimate power output. However:

• Determining the exact rotational inertia of in-service engines was difficult,

• The method was never widely adopted.

Currently, engine power is mostly estimated indirectly from the machine’s operational characteristics.

3. Methods for Different Transmission Types

a) Hydrodynamic (Torque Converter) Transmission Machines:

• First, compare operational performance indicators to those of a new machine.

• If the differences are small, the engine power is likely within the standard range.

• Focus on: full-speed travel, RPM drop under full load, cycle time of working operations.

b) Mechanical Transmission Machines (e.g., pure mechanical dozers):

• Check track slippage under full load.

• Adjust main and steering clutch free plays if slippage is excessive.

• Conduct high-speed travel tests and compare with new-machine standards.

• Note: This is only an estimate; efficiency losses and component wear affect accuracy.

c) Turbocharged Engines:

• For engines with exhaust turbochargers, boost pressure can serve as an indirect indicator of engine output.

• Typical absolute boost: 85–145 kPa.

• Adjust machine performance to nominal values and perform full-load tests.

• If boost reaches specification, engine power is likely normal.

d) Hydraulic Transmission Machines (constant-power systems, e.g., hydraulic excavators):

• Easier to estimate in-service engine power.

• Principle: hydraulic transmission delivers constant power output, so engine runs at full power under full load.

• Test cycle times of single operations to estimate engine power range.

4. Example: Excavator Engine Power Estimation

Machine: Excavator, 9,270 hours, operator reports slow movements.

Cold Engine Test (hydraulic oil <50°C, main relief valve 35,000 kPa):

Analysis:

• Boom lift: 77% of new-machine performance (low)

• Swing speed: 90% (acceptable)

• Stick extension: 80% (low)

• Stick retraction: 80% (low)

• Travel speed: ~80% (acceptable)

Hydraulic system efficiency: ~92%
Estimated engine power drop: ~5%

After fuel system cleaning and filter replacement:

• Engine power (under stall conditions) restored to ~98%

• Hydraulic circuit cycle times restored to 85–91%, within acceptable range.

Hot Engine Test (hydraulic oil ~55°C, main relief 34,600 kPa):

• Full-load RPM drop to 1,780 rpm (~98% of rated speed)

• Engine power loss within acceptable range

• Adjust hydraulic system per factory requirements, perform full-machine performance test

• All action cycle times ~10% below new-machine specs

Conclusion: Minor main hydraulic pump wear observed; performance still acceptable, but monitor and plan maintenance when performance drops to ~80%.

5. Key Observations

• Most in-service engine power loss is due to poor maintenance, not severe wear.

• Early engine wear is often also caused by improper maintenance.

• Proper maintenance is critical for construction machinery engines.

Example: Fuel filter replacement

• Many operators replace filters only when clogged.

• At clogging point, large dirt particles may already have passed the filter, entering the fuel system.

• Recommendation: replace filters on schedule, not after clogging (unless equipped with differential pressure monitoring).

Note: Modern paper filters do not perform as well as old-style slit filters, which increased filtration efficiency as they clogged.

This provides a comprehensive understanding of how to estimate and evaluate engine power in operational construction machinery, emphasizing maintenance, measurement, and practical assessment rather than relying on a single “magic method.”