What is a radial car engine?

This blog post will answer the question, ‘What is a radial car engine?’, and cover topics like how does a radial car engine work, and merits and demerits of a radial car engine.

What is a radial car engine?

A radial engine is a type of IC engine that works in a reciprocating manner. The cylinders of a radial engine protrude outwards from a centralized crankcase.

A radial engine can be summarized in the following ways:

  • It is an engine with pistons positioned in a circular plane around the central crankcase.
  • The connecting rods of the pistons are connected to a master rod which, in turn, is connected to the crankshaft
  • In a radial engine, the bank of cylinders always has an odd number of cylinders ranging from 3 to 13 or even more.
  • Operating on a four-stroke cycle, every other cylinder fires and has a power stroke as the crankshaft rotates, providing a smooth operation
  • Other applications of radial engines lie in large-sized propeller-driven aircraft.
  • Large ship engines also use radial engines with up to 54 cylinders, and six banks of 9 cylinders each.

How does a radial car engine work?

Radial engines employ the use of poppet valves that are located right above the cylinders. The poppet valves are operated by means of a pushrod, which are in turn controlled by the cams from the camshaft. The camshaft rotates in a direction opposite to that of the crankshaft.

The active stroke operating in a radial engine cylinder allows the next firing cylinder to compress and thus develops a uniform range of motion. This uniformity or the uniformly timed cycle would not have been ideal in the case of an even number of cylinders.

A typical 4-stroke engine comprises the four different working strokes and a pair of cam lobes control the opening and closing of the inlet and exhaust valve respectively. In the case of radial engines, there are fewer cam lobes required to operate.

A radial engine, since it has an odd number of cylinders, alternates the firing order. If a radial engine houses 5 cylinders, the order of firing would be 1,3,5,2,4.

Merits and demerits of a radial car engine

These are the following merits and demerits associated with a radial car engine.


Maintaining a radial car engine is easy

A radial engine construction is simple and is done in such a way that it aids in performing fixes and regular maintenance work. It can also be kept running for a while.

Tough build

The simple design of a radial engine grants it another perk, that is its tough build which reduces its vulnerability to suffering damage.

Smooth experience

Radial engines help in generating power with great consistency as compared to other water-cooled engines, thus allowing it to run smoothly.


One of the most distinctive features of a radial engine is that it consists of a shorter crankshaft on which it houses all the cylinders, as compared to other engines.

This simple design of a radial engine helps in reducing noise and vibrations produced by the car to a minimum. It also reduces the wear and tear of the engine and its related components, while increasing the life of the engine greatly.


Radial engines are very versatile as they have a wide range of applications. For example, many medium and large-sized propeller-driven aircraft deploy radial engines.

In the case of a large aircraft, two or more banks of cylinders are mounted together with one cylinder behind the other. This arrangement is all done on a single crankshaft, thus allowing the production of a powerful and smooth engine.

Cost of production

Engines generally are not that cheap when it comes to their maintenance and related expenditures.

Radial engines on the other hand have cheaper parts, repairs, and even maintenance expenditures, and thus are more appealing for the market.


Engine drag

Engines being exposed to the atmosphere, increase the drag force on the vehicle may hinder acceleration purposes, and can also increase the fuel consumption rate.

Can affect vision

Since the radial engines comprise spoke-like formations to house the cylinders, they can affect the driver’s field of vision.

Difficult to install

Since the radial engines are air-cooled, they become difficult to install along with the engine.

Research has shown the various cars that have tried to implement the concept of radial engines.


This blog post addressed the question, ‘What is a radial car engine’.

We came to understand the ways in which a radial engine works and also learned about its unique construction. The wide applications of radial engines have been discussed as well, underlining their versatile nature. Furthermore, detailed merits and demerits list has also been provided. Please feel free to comment on the content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): What is a radial car engine?

Are radial engines efficient?

Radial engines can be 20% more efficient, thus granting it the ability to produce more power with a lesser amount of fuel consumed.

Why don’t we use radial engines in cars?

Radial engines although applicable, are not common in modern cars. This is mainly due to the fact that it would take up too much space alongside the various mechanical and electrical components inside a car.

Why did Japan use radial engine?

The primary reason behind Japan using a radial engine is solely due to the fact that radial engines offer a better power to weight balance and are also more reliable due to their simple design when compared to the in-line engines.