Why is the compression ratio of petrol engines lower compared to diesel engines?

Question

Accepted Answer

Petrol engines have lower compression ratios compared to diesel engines.

Petrol engines have lower compression ratios to prevent knocking or detonation.
Diesel engines have higher compression ratios to ignite the fuel without spark plugs.
Higher compression ratios in diesel engines result in better fuel efficiency and torque.
Petrol engines require lower compression ratios to accommodate the lower octane rating of petrol fuel.
Lower compression ratios in petrol engines allow for smoother operation and quieter combustion.

Accepted Answer

The compression ratio in diesel engines is typically higher than in petrol engines because diesel engines rely on compression ignition, where the fuel ignites due to the heat generated by compressing air in the cylinder. Higher compression ratios in diesel engines lead to better efficiency and power output. Petrol engines, on the other hand, use spark ignition, so they don't require as high compression ratios.

Accepted Answer

lack of a spark plug

Accepted Answer

Diesel, on the other hand, requires the cylinder to compress the air to the point where injecting diesel fuel instantly combusts the air-fuel mixture. This is why a diesel engine has a higher compression ratio as it compresses a larger volume of air per cylinder to ensure the fuel can be used for combustion

Accepted Answer

Diesel, on the other hand, requires the cylinder to compress the air to the point where injecting diesel fuel instantly combusts the air-fuel mixture. This is why a diesel engine has a higher compression bustionratio as it compresses a larger volume of air per cylinder to ensure the fuel can be used for com

Accepted Answer

Because petrol engine ignition point low and this engine use spark plug

Accepted Answer

Diesel is not as volatile as petrol and hence it is directly injected into theengine cylinder. ... Therefore dieselcan be ignited by heat generated bycompression of air inside a cylinderwhich requires higher compression ratio whereas a petrol engine uses spark ignition and hence has lower compression ratio.

Accepted Answer

Engines are all about controlled burning or should I say technically OXIDATION, and utilization of resultant heat energy produced(OR Should I say Pressure Energy of Gases) to perform mechanical work. Now the important point herein is the fuel that we are burning inside engine. Petrol engine uses Petrol & Diesel Engine utilizes Gasoline (Diesel). Both have different styles of getting the same work done. Petrol engine utilizes the compression & ignition of petrol for its combustion while Diesel Engine utilizes compression of input air only for combustion. And the rest of the mechanism is same for both the engines. The different styles of combustion are due to different chemical properties of fuel burned, the main being volatility of fuel. Petrol is more volatile than Diesel and hence its burning has to be more controlled. That is the main reason why petrol engines have lower compression ratio so that fuel doesn't oxidezes from compressed gases only and it would require a spark from spark plug to achieve combustion. But sometimes due to faulty cooling system, pre-ignition occurs which is never desirable. One good benifit of this controlled combustion is also that petrol engines are light in weight (viz Diesel Engines) that improves its fuel economy as well.

Why is the compression ratio of petrol engines lower compared to diesel engines?

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