what is blow by on a diesel engine

Championisme authors

2 min read

·

16-10-2024

24

0

Share

Blowby: The Enemy of Diesel Engine Efficiency

What is blowby?

Blowby refers to the phenomenon where combustion gases from the combustion chamber leak past the piston rings and into the crankcase of a diesel engine. This unwanted leakage can significantly impact engine performance, fuel efficiency, and longevity.

Why does blowby occur?

Blowby is a natural byproduct of the high pressures and temperatures present in a diesel engine during the combustion cycle. Here are some key contributing factors:

• Worn Piston Rings: As piston rings wear down, they lose their ability to maintain a tight seal between the piston and cylinder wall, allowing combustion gases to escape.
• Excessive Ring Gap: The gap between the piston rings and cylinder wall can be too large, allowing blowby to occur. This gap is designed to allow for thermal expansion and contraction, but if it's too wide, combustion gas can escape.
• Excessive Cylinder Bore Wear: Excessive wear on the cylinder wall can also lead to a loss of seal, resulting in blowby.
• High Combustion Pressure: Diesel engines operate at higher combustion pressures than gasoline engines, leading to greater potential for blowby.
• Incorrect Valve Timing: Incorrect valve timing can cause blowby by allowing combustion gases to escape before the exhaust valve opens, increasing the pressure in the cylinder.

How does blowby affect a diesel engine?

Blowby can lead to several detrimental effects on your diesel engine:

• Reduced Engine Power: Blowby reduces the effective compression ratio, leading to a decrease in engine power.
• Increased Fuel Consumption: As combustion gases escape, fuel is not burned as efficiently, leading to higher fuel consumption.
• Oil Contamination: Blowby contaminates the engine oil with combustion byproducts, accelerating oil degradation and leading to increased wear.
• Engine Noise: Blowby can create audible noises, particularly when the engine is under load, signaling a potential issue.
• Increased Emissions: The escaping combustion gases can contribute to increased emissions, potentially impacting environmental regulations.

How can you prevent blowby?

While some blowby is inevitable, these preventative measures can help minimize its impact:

• Regular Maintenance: Maintaining proper oil levels and performing regular oil changes can help to mitigate the effects of blowby on engine oil.
• Proper Lubrication: Using the correct engine oil viscosity and ensuring proper lubrication is crucial for reducing wear on piston rings and cylinder walls.
• Engine Tune-Ups: Regularly inspecting and adjusting valve timing can help ensure optimal combustion and minimize blowby.
• Replace Worn Parts: Worn piston rings, cylinder liners, and other related components should be replaced when necessary to maintain a tight seal.

Further Insights from Research:

• "Impact of blow-by on diesel engine emissions and performance" by S.M. Sarvi et al. (2012): This study highlights the significant impact of blowby on emissions, particularly particulate matter (PM), hydrocarbons (HC), and carbon monoxide (CO). The authors suggest that reducing blowby through improved engine design and maintenance practices can contribute to cleaner emissions.
• "The effect of blow-by on diesel engine performance and emissions" by M.A. Javed et al. (2016): This study explores the impact of blowby on fuel consumption and NOx emissions. The research indicates that blowby can negatively impact fuel economy and increase NOx emissions, highlighting the need for mitigation strategies.

Conclusion:

Blowby is a significant challenge in diesel engine operation, impacting performance, fuel economy, and emissions. Understanding the causes and consequences of blowby is crucial for ensuring efficient and reliable engine operation. Regular maintenance, proper lubrication, and prompt replacement of worn components are vital for minimizing blowby and maximizing the lifespan of your diesel engine.