discuss the characterstics of DIand IDI diesel engine

 Sure! Here's a clear and detailed answer for your (ii) part: Characteristics of DI and IDI diesel engines (8 marks):

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Characteristics of DI (Direct Injection) and IDI (Indirect Injection) Diesel Engines

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Direct Injection (DI) Diesel Engines

Definition:
In DI engines, fuel is directly injected into the main combustion chamber (cylinder) above the piston.

Characteristics:

• 🔹 High Thermal Efficiency: Less heat loss, better fuel economy.

• 🔹 Higher Power Output: Due to better combustion efficiency.

• 🔹 Better Cold Start with Modern Systems: (Earlier DI engines had poor cold start; now glow plugs help.)

• 🔹 Lower Fuel Consumption: More complete combustion.

• 🔹 High Injection Pressure Needed: Fuel must atomize finely to mix with air.

• 🔹 More Noisy: Sharp combustion noise (diesel knock) if not controlled.

• 🔹 More Complex Injection System: Need precise control.

• 🔹 Less Heat Loss: Because combustion happens in the main chamber.

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Indirect Injection (IDI) Diesel Engines

Definition:
In IDI engines, fuel is first injected into a small pre-combustion chamber. Combustion starts there and then spreads to the main chamber.

Characteristics:

• 🔸 Lower Thermal Efficiency: Some heat is lost in pre-chamber walls.

• 🔸 Lower Power Output: Less efficient than DI engines.

• 🔸 Better Cold Starting: Easier to start in cold climates without much help.

• 🔸 Higher Fuel Consumption: Because of lower efficiency.

• 🔸 Lower Injection Pressure: Fuel does not need very high pressure.

• 🔸 Smoother and Quieter Operation: Less diesel knock.

• 🔸 Simpler and Cheaper Injection System: No need for very high precision.

• 🔸 More Heat Loss: Heat is absorbed by pre-combustion chamber.

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Comparison Table

Feature	DI Engine	IDI Engine
Injection Location	Direct into main chamber	Into pre-combustion chamber
Fuel Efficiency	High	Lower
Power Output	Higher	Lower
Cold Starting	Harder (but improved today)	Easier
Engine Noise	Higher	Lower
Injection Pressure	Very High	Moderate
System Complexity	High	Simple
Heat Loss	Less	More

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Summary

• DI engines are more fuel-efficient and powerful, but noisier.

• IDI engines are smoother and quieter, but less efficient and consume more fuel.

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Would you also like a simple diagram showing DI vs IDI combustion chambers? 🚗🛠️ It looks great in an answer sheet and makes it easy to understand!
I can quickly draw that for you too if you want! 🎯✨

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