With reference to a turbocharged engine fitted with charge air cooler, It is noticed that boost pressure at the inlet manifold is reducing over a period of time:
(a) list FOUR possible causes; stating a simple and economical in service maintenance routine that would rectify EACH(8)
(b) state the effect reduced inlet pressure at full load will have on the engine.(2)
Possible Causes of Reducing Boost Pressure
A decrease in boost pressure over time in a turbocharged engine with a charge air cooler can be attributed to several factors:
Turbocharger Related Issues
- Turbine Efficiency: Reduced turbine efficiency due to wear, fouling, or damage can decrease the amount of air compressed.
- Compressor Efficiency: Similar to the turbine, wear or damage to the compressor can reduce its ability to compress air.
- Wastegate Malfunction: A stuck-open wastegate can bypass exhaust gases, reducing turbine speed and boost pressure.
- Turbocharger Seal Failure: Internal leakage within the turbocharger can reduce the amount of air delivered to the engine.
Charge Air Cooler Related Issues
- Clogged Cooler: The charge air cooler fins can become blocked with dirt, debris, or oil, reducing airflow and increasing backpressure.
- Leaking Cooler: If the charge air cooler develops leaks, it can bypass compressed air, reducing boost pressure.
Intake System Issues
- Intake Restrictions: Blockages or restrictions in the intake system, such as the air filter or intake pipes, can reduce airflow and boost pressure. 1. Low Turbo Boost Pressure Causes and Symptoms www.mpgtuning.co.uk
- Intercooler Piping: Leaks or restrictions in the intercooler piping can also reduce boost pressure.
Engine Management System Issues
- Sensor Malfunction: Faulty boost pressure sensors or other sensors related to engine control can provide incorrect data, leading to reduced boost pressure.
- ECU Issues: Problems with the engine control unit (ECU) can affect boost pressure control and management.
To accurately diagnose the root cause, it’s essential to perform a systematic inspection of the turbocharger system, including the turbocharger itself, charge air cooler, intake system, and engine control components.
Diagnosing Reduced Boost Pressure
Diagnosing the root cause of reduced boost pressure requires a systematic approach. Here are some steps to consider:
Visual Inspection:
- Turbocharger: Check for signs of damage, oil leaks, or excessive wear. Inspect the turbine and compressor wheels for any abnormalities.
- Charge air cooler: Look for signs of damage, leaks, or blockages in the intercooler and its piping.
- Intake system: Inspect the air filter, intake pipes, and connections for any restrictions or damage.
- Exhaust system: Check for blockages or restrictions in the exhaust system that could affect turbocharger performance.
Performance Checks:
- Boost pressure gauge: Monitor boost pressure under various load conditions to identify any inconsistencies.
- Exhaust gas temperature (EGT): Measure EGT to assess turbocharger efficiency and identify potential issues.
- Engine performance: Observe engine performance, such as power output and smoke levels, for any indications of problems.
Diagnostic Tools:
- Turbocharger test bench: If available, testing the turbocharger on a test bench can help isolate issues.
- Pressure gauges: Use pressure gauges to measure boost pressure at different points in the system.
- Exhaust gas analyzer: Analyzing exhaust gases can provide clues about engine combustion and turbocharger performance.
Potential Tests:
- Turbocharger wastegate actuator: Check for proper operation and no sticking.
- Intake system pressure drop: Measure the pressure drop across the air filter and intake system.
- Charge air cooler performance: Evaluate the cooler’s efficiency by measuring inlet and outlet air temperatures.
By following these steps and using appropriate diagnostic tools, you can effectively identify the root cause of the reduced boost pressure and take corrective action.
Effects of Reduced Inlet Pressure on the Engine
A reduction in inlet pressure to an engine can have several negative impacts on its performance and efficiency:
- Reduced Power Output: Less air entering the combustion chamber means less oxygen available for combustion, resulting in decreased power output.
- Increased Fuel Consumption: To maintain the same power level, the engine will require more fuel, leading to higher fuel consumption.
- Incomplete Combustion: A lean air-fuel mixture due to reduced air intake can cause incomplete combustion, leading to higher emissions and potential engine damage.
- Increased Turbocharger Load: The turbocharger must work harder to compress the reduced amount of air, potentially leading to increased wear and tear.
- Detonation: In severe cases, a lean air-fuel mixture can lead to engine knocking or detonation, causing damage to engine components.
Overall, a reduction in inlet pressure has a detrimental effect on engine performance, efficiency, and durability.