How does the compression ratio matter in your vehicle engine?
It depends on which engine your vehicles have whether it is Diesel or Petrol Engine. During compression stroke how much air-fuel mixture in Gasoline/Petrol Engine or only air in Diesel Engine, mixture or air molecules compressed in the engine cylinder combustion chamber. Normally the Compression Ratio (CR) of diesel engines has much higher than that of petrol engines. Those vehicles engines higher compression ratio can improve both power and efficiency. Higher compression ratios contribute to the more proper burns of air-fuel, it also increases combustion temperature. The more compressed the mixture the better it burns or ignites, which gets more power and is more efficient, but one drawback is that the engine produced more nitrogen oxide (Nox) emissions. In the simple term to understand, higher combustion temperature and higher compression ratio lead to creates more Nox exhausts emissions produced. In generally Diesel engine has a higher compression ratio in the technical term Diesel engine called compression ignition.
Gasoline (Petrol) Engine compression ratio is lesser as compared to diesel engine because petrol engine has spark plug to ignition air-fuel mixture. At the end of the compression stroke, the spark plug provides the spark to ignite the air-fuel mixture and another reason for the compression ratio is less in the petrol engine. Petrol engine cause to knock due to higher Compression, the air-fuel mixture gets heat up during compression stroke so the mixture gets hot enough air-fuel mixture before spark or ignition it such called engine knock, that is reasons higher compression ratio (CR) increase to chances of knocking this limits the ratio of compression that why gasoline petrol engine has lower compression ratio compared to diesel engine.
Compression Ratio (CR) of Gasoline (Perrol) Engines from 10:1 to 14: 1, and Diesel Engine the varies from 18:1 to 23:1. It varies for several reasons of vehicles engine configuration and also matters overall performance and efficiency in your vehicle engine.
Why is the diesel engine compression ratio higher than the petrol engine?
In literally, Petrol engines are drawn into the engine cylinder during Suction/Intake Stroke air-fuel mixture into the cylinder. During the compression stroke, the engine piston pushes or compressed air-fuel mixture from the bottom dead centre to the top dead centre (BDC to TDC). Mixture air-fuel is quite a large volume molecule as compared to a diesel engine, In diesel engines, during suction/Intake stroke only air intake from the atmosphere so while compression stroke air becomes hot and less dense, compressed hot air has a lesser volume so that diesel engines have to pursue higher compression ratio (CR). Other several factors also matter on compression ratio mainly engine cylinder bore stroke ratio and different engine configuration and engine specification.
Some of the reasons behind mentioned below:
• Engine Cylinder Bore and Stroke.
• The thickness of the head gasket which is placed in between the cylinder head and cylinder block.
• The diameter of the head gasket (the bore of the head gasket).
• The distance between piston top and cylinder block level.• The volume of the engine piston dish and dome and the last engine combustion chamber volume.
Let's take an example:
The total volume engine cylinder = 1000 CC it means TDC to BDC when the engine Piston is Bottom Dead Centre. It is also called swept volume. e.g V¹. Next Clearance Volume means Engine piston when travelling Top Dead Centre (TDC) e.g V².
Total Volume= 1000 CC/ 1 Liter.
Swept Volume= 900 CC.
Clearance Volume= 100 CC.
Compression Ratio = Swept volume (V¹) / Clearance Volume (V²) = 1000/100 = 10/1, 10:1.
0 Comments