The power to weight ratio of a diesel engine compared to a petrol engine is

🔑 Key Points
⚙️ Concept:
→ The compression ratio for diesel engines ranges from 16:1 to 22:1, while for petrol engines it is between 6:1 to 12:1.
→ Diesel engines (C.I. Engines) are larger and heavier than petrol engines (S.I. Engines) because of the higher compression ratio.
→ For the same power output, the power-to-weight ratio is lower for diesel engines compared to petrol engines.
→ The compression ignition process in diesel engines requires a higher compression ratio to achieve the self-ignition temperature of the fuel.
→ Compression ratio (r) is defined as the ratio of the volume before compression to the volume after compression.
Formula: r = (Vc + Vs) / Vc,
where Vc is clearance volume and Vs is swept volume.

🚗 Difference between C.I. Engine and S.I. Engine:
→ C.I. Engine (Diesel Engine):
→ Works on the Diesel cycle.
→ Uses diesel as fuel.
→ Uses injectors for fuel injection.
→ Ignition occurs from high temperatures after the compression stroke.
→ Compression ratio is between 16:1 to 22:1.
→ Provides higher thermal efficiency.
→ Has more weight per unit power.
→ Produces high torque at lower speeds.

→ S.I. Engine (Petrol Engine):
→ Works on the Otto cycle.
→ Uses petrol or gasoline as fuel.
→ Uses a carburetor for the air-fuel mixture.
→ Ignition occurs with a spark plug.
→ Compression ratio is between 6:1 to 12:1.
→ Has lower thermal efficiency.
→ Has less weight per unit power.
→ Produces less torque but operates at higher speeds.