Why is compression ratio higher in CI engines as compared to SI engines?

CI engines are heavier and the fuel is burned heterogeneously, hence producing lower speeds. Thermal efficiency of the engine: In the case of CI engines the value of compression ratio is higher; hence these engines have the potential to achieve higher thermal efficiency.

What is the compression ratio of Si engine?

In the SI engine, fuel is mixed with air, broken up into a mist, and partially vaporized. The compression ratio varies from 4:1 to 8:1, and the air–fuel mixture ratio varies from 10:1 to 20:1. The four strokes of a petrol engine sucking fuel–air mixture are shown in Fig. 2.2.

Why do we not use the same technology to start both SI and CI engines?

Because due to the type of fuel used in each engine!!! In SI engine, petrol has high self ignition point (247–280 C) i.e petrol requires that high temp. to start combustion. It is not possible that the SI engine can’t provide such high temps.

What are the differences between SI and CI engines?

Difference Between Si engine and Ci engine Si engine is internal combustion engine that operates on the principle of spark ignition. It uses petrol and utilizes the Otto cycle. The diesel (Ci) engine is also an internal combustion engine, which uses diesel fuel and operates on diesel cycle.

What is high compression ratio?

If an engine has a high compression ratio, it means that a given volume of air and fuel in the cylinder is being squeezed into a much smaller space than an engine with a lower compression ratio.

What happens if compression ratio is too high in diesel engine?

(1) With high compression ratio, they operate at higher pressures and offer a cleaner and complete burn of fuel leading to better mileages too. However, it’s not ALL good. The higher pressure requires stronger build of the engine (in some cases heavier). Chances of knocking in the engine are higher.

Which of the following is not true about the compression ignition engine?

4. Which of the following does not relate to a compression ignition engine? Explanation: Carburetor is not related to compression ignition engine.

What is the advantage of compression ignition engines vs spark ignition engines?

CI engines have higher Mechanical Efficiency It does not need to manage the intake of air as it is operated with a heterogeneous mixture, thus the control of the load can be managed by the quantity of fuel injected into the cylinder.

Why do we not use the same technology to start both Si CI engines?

Why SI engines are high speed engines?

SI Engines operates at higher speed due to their less compression ratio (i.e. less weight per unit power). They produce less torque and operates at higher speed.