Difference Between Otto Cycle and Diesel Cycle [Notes & PDF]

The main difference between Otto and Diesel cycle is that The otto cycle explosion process takes place at a constant volume process and the Diesel cycle explosion process takes place at a constant pressure process.

In this article, we will be studying the differences between Otto and Diesel cycle in very detail.

Note: At the end of the articles, you will find the PDF which you can easily download.

Otto Cycle:

The cycles are mostly found in an automobile engine. The fuel used in the Otto cycle is Petrol fuel.
The heat addition takes place at a constant volume process and It is also known as the Isochoric process.

Diesel Cycle:

The fuel used in the diesel cycle is diesel fuel.
In the diesel cycle, the heat addition takes place at constant pressure and It is also known as the Isobaric Process.
Here you can read Diesel Cycle in detail.

The below figure is attached PV and TS Diagram of Otto and Diesel cycle.

Otto Cycle	Diesel Cycle
1-2: Isentropic Compression	1-2: Isentropic Compression
2-3: Heat Addition at constant volume	2-3: Heat Addition at constant Pressure
3-4: Isentropic Expansion	3-4: Isentropic Expansion
4-1: Heat rejection at constant volume processes.	4-1: Heat rejection at constant volume processes.

Cycle Process

Difference between Otto and Diesel Cycle

Difference Between Otto Cycle and Diesel Cycle:

Sl No.	Otto Cycle	Diesel Cycle
1.	Otto cycle has low thermal efficiency.	The diesel cycle has high thermal efficiency.
2.	It has a low compression ratio.	But This one works on a high compression ratio.
3.	Otto cycle is also called a Constant volume cycle.	The diesel cycle is called a constant pressure cycle.
4.	Otto cycle system is light in weight. But	The diesel cycle is heavy in weight.
5.	The explosion process takes place at constant volume process and	In the diesel engine, the explosion process takes place at a constant pressure process.
6.	The Spark Plug is used here for igniting the charge.	A fuel injector is used here for igniting the charge.
7.	A mixture of air and fuel is entered in suction stroke.	Only air is entered in suction stroke.
8.	Here the working fuel is used as Petrol.	The working fuel is used as Diesel.
9.	Otto cycle engine is the high-speed engines.	Diesel cycle engines are not high-speed engine comparatively Otto cycle.
10.	The engine starting is easy in cold weather too.	But here it is difficult comparatively Otto cycle.