How do Diesel Engines Run Without Spark Plugs?

Nowadays, the prices of fuel are rising day by day. Thanks to the incredible invention of diesel fuel that is not just efficient but cost effective at the same time. The reason behind this engine being so affordable is that it does not need a spark plug (as needed in petrol engines). Now, one question must be popping in your mind “how on earth diesel engines run without spark plugs?” Well, there is no rocket science behind it.

Just a little difference in the functioning leads this engine to ignite without needing a spark plug and run your car smoothly.

Major Reason behind Diesel Engines Run Without Spark Plugs

Let’s find out the vital reasons for diesel engine being sparking without requiring a spark plug at all, right now!

1. Low Volatility

In diesel engines, the infusion of air and fuel takes place at different stages. The ratio of compression may lead from 14:1 to 25:1. The idea behind designing the diesel engine is to have higher compression ratios. Less volatile nature of the diesel, as a result, tends it to have a low self-ignition temperature.

However, another reason is their power cycle according to which the higher compression ratio (mentioned above) is not possible to achieve by petrol, as the chances for onset auto- ignition or engine knock are high.

2. Self-Ignition Temperature

Due to the lower self-ignition temperature property of diesel than those of petrol and gasoline, the temperature generated by the compression of air while compression stroke is on the action, enough to ignite the atomized diesel fuel. The temperature could be 1000F or higher, which is enough to ignite the fuel. This clearly shows that diesel engine is an improvement over petrol engines as in these engines only air is compressed during compression stroke making them capable of working even at the much higher temperature ratio as well.

Major reasons for diesel engines run without spark plugs
Why diesel engines run without spark plugs. Source: CarTreatments

On the other hand, petrol engines have an inability to work at higher temperature ratios even if they do work at some high temperature, air-fuel mixture may pre-ignite. This can result in knocking and detonation and for that, you might also require some maintenance tips as well. This is why the lesser self-ignition temperature capability makes the diesel engine an improved version of SI (petrol) engine.

So, this is how diesel engines run without spark plugs efficiently and quickly.

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3. Neglected Usage of Spark Plug

The atmospheric air stuck in the cylinder of the diesel engine, which then gets compressed to high pressure. This process eventually increases the temperature and as the engine came into action at the end of compression stroke, ignition happens and fuel burns. This naturally eliminates the requirement of a spark plug to ignite the engine.

Diesel engines run without spark plugs to save fuel
Diesel engines run without spark plugs due to overuse of Spark Plug. Source:

So, this is why the diesel engine doesn’t require spark plug in addition these engines have overcome the disadvantage of earlier engines like noise and spark plug maintenance. Therefore, diesel engines run without spark plugs to save the fuel, time, and money at the same time.