CLASSIFICATION OF IC ENGINE: Ignition types & Engine cycles.



(a) Spark ignition (SI).

The SI engine uses spark plugs to initiate the combustion process at every cycle.

The spark plug creates a high voltage discharge between the two electrodes and ignites the air-fuel mixture in the combustion chamber that surrounds the plug.

In early engine development, before the invention of electric spark plugs, used many forms of flare to initiate combustion with an external flame.

(b) Compressive ignition (CI).

The combustion process of the IC engine begins when the air-fuel mixture self-ignites due to the high temperatures in the combustion chamber due to high compression.


(a) 4-stroke cycle.

In a four-stroke cycle, each cycle produces four piston movements over two engine revolutions.

(b) 2-stroke cycle.

In a two-stroke cycle, two pistons move at one revolutions per cycle.


(a) Valve in head (overhead valve).

Also known as an I-head motor.

(b) Valve (flat head) in the block.

Also called an L head engine.

Some historic valve block engines had an intake valve on one side of the cylinder and an exhaust valve on the other side.

These were called T-head motors.

(c) One valve on the head (usually an inlet), one on the block, also known as the F-head engine.

It’s much rarer.


(a) Reciprocating.

The engine has one or more cylinders in which the piston moves back and forth.

The combustion chamber is located at the closed end of each cylinder.

Power is supplied to the rotary output crankshaft via a mechanical connection to the pistons.

(b) Rotary.

The engine consists of a large non-concentric rotor and a block (stator) built around the crankshaft.

The combustion chamber is built into a non-rotating block.


(a) Single cylinder.

The engine has a cylinder and piston connected to the crankshaft.

(b) Inline.

The cylinders are aligned back and forth along the crankshaft.

Can consist of 2 to 11 cylinders or, in some cases, more cylinders.

The in-line 4-cylinder engine is widely used in automobiles and other applications.

In-line 6-cylinder and 8-cylinder engines are historically popular automobile engines.

A in-line engine is sometimes referred to as a straight (eg straight 6 or straight 8).

(c) V engine.

Two cylinder banks angled to each other along one crankshaft.

The angle between the cylinder banks is between 15 ° and 120 °, typically 60 ° and 90 °.

The V engine has an even number of cylinders from 2 to 20 or more.

The V6 and V8 are common car engines, and the V12 and V16 are (historically) found in some luxury and high performance cars.

(d) Counter cylinder engine.

Two opposite cylinder banks on one crankshaft (180 ° W engine).

These are common small planes and some cars with two to eight or more even cylinders.

These engines are often referred to as boxer engines (e.g, flat four).

(e) W engine.

Same as a V engine, except that it has three cylinder on the same crankshaft.

Although uncommon, some are designed to race cars both in modern times and in history.

Normally 12 cylinders with an angle of 60°.

(f) Piston engine on the other side.

Each cylinder has two pistons and the combustion chamber is in the middle of the pistons.

A single combustion process causes two power strokes at the same time, pushing each piston out of the center and powering a separate crankshaft at each end of the cylinder.

The engine output is either two rotary crankshafts with complex mechanical connections or one crankshaft.

(g) Radial engine.

A engine with pistons placed in a circular plane around the central crankshaft.

The connecting rod of the piston is connected to the master rod.

The master rod is connected to the crankshaft.

The cylinder of a radial engine always has an uneven number of cylinders of 3 to 13 or more.

In a 4-stroke cycle, as the crankshaft rotates, every other cylinder ignites and produces an expansion stroke, allowing for smooth operation.

Many medium and large propeller aircraft use radial engines.

On large aircraft, two or more are mounted back and forth on one crankshaft, making the a powerful and smooth engine.


Internal combustion engines are more efficient and lighter than the developed outputs.

These are very suitable for mobile applications.

All of these advantages make internal combustion engines a universal means of power generation and are extremely popular.


The types of fuels that can be used are limited to very high quality gaseous and liquid fuels.

The fuel used is very expensive, like gasoline and diesel.

The emissions of a engine are generally higher than those of an internal combustion engine.

Not suitable for large power generation


(i) Passenger car
(ii) Truck / Bus
(iii) Off highway


Light aircraft.

(i) Outboard
(ii) Inside
(iii) Ship

Power generation:
(i) Portable (domestic)
(ii) Fixed (peak power)

(i) Tractor
(ii) Pump unit

Civil engineering work:
(i) Damper
(ii) tripeers
(iii) Mining equipment

Household use:
(i) Lawnmowers
(ii) Snow remover
(iii) tool

Leave a Comment

Your email address will not be published.