How Many Spark Plugs are in a Diesel Engine?
One word answer to the question in the title ‘how many spark plugs are in a diesel engine?’ is – NONE,
This is because a diesel engine is vastly different than your regular gasoline (Petrol) engines. be it the structure or working of the two, the only similarity there is that both comes under the tree of internal combustion engine. The main factor to focus on here is how they achieve the combustion. Also both of them use the fuel in entirely different ways, giving them their signature characteristics.
The gasoline engines depend on the Spark plugs on the other hand the Diesel engines depend on the Glow plugs. But the question is what the difference between these two is? its’ aslo common for people still wonder how many spark plugs are in a diesel engine, only to find diesel engine doesn’t use spark plugs at all. In the below sections we will discuss this difference along with some other characteristics.
Glow Plugs
These plugs help the diesel engine to get started due to two main reasons, one is the vehicle is working in the colder weathers and the second one is a bit chemical, i.e. the boiling point of diesel is slightly higher than petrol. Due to this a short spark is not enough to ignite the fuel in Diesel engine. The exact working is explained with the help of the below pointers
- They warm up the combustion chamber so that the diesel fuel can be ignited effectively. Fuel ignition in diesel engines relies on the heat created by compressing air rather than a spark. In cold temperatures, however, it becomes difficult to heat the air due change in the air pressure. Glow plugs assist by warming up the air within the combustion chamber so that ignition can be smooth and continuous when the engine is being started.
- This is quite important in cold starts, in which air and fuel only might not be enough to attain ignition temperature. Cold conditions have a serious impact on the ignition process of diesel engines since the air pulled into the cylinders is seriously cooler. The fuel-air mixture will not ignite effectively without sufficient initial heat. Glow plugs solve this issue by producing additional heat, and it becomes easier to start the engine consistently even at freezing temperatures. Other than higher boiling point of diesel, its higher density also play a key role due to which the diesel engines have this type of ignition.
- Glow plugs emit a red-hot glow, warming the air/fuel mixture prior to and during engine starting. When you turn the key or press the start button in a diesel engine, the glow plugs heat up quickly—reaching temperatures over 1000°F (538°C). This hot heat guarantees that the fuel burns properly during engine cranking. Certain systems maintain the glow plugs on for a brief period after the engine is started to assist with smooth idling and reduced emissions.
- The higher calorific value of diesel as a fuel also plays a crucial role, why these engines use glow plugs and not spark plugs. this is because the energy must be used to its last bit, and the finest way to ensure is by igniting the diesel + air mixture through hot air compression
All of the above reasons will give you a good picture about why diesel engines do not have spark plugs or how many spark plugs are in diesel engines.
Spark Plugs
These on the other hand, have quite straightforward working and simpler mechanics, all thanks to lower boiling point of petrol and its lower density as compared to diesel.
When you start the vehicle, the ignition system sends a high voltage current to the spark plugs. Due to this each spark plug creates a small but accurate and perfectly timed spark that ignites the mixture of air and fuel present in the ignition chamber of the engine. This happens continuously in each cylinder while the engine is running.
You can clearly see how different the working of a spark plug is from a Glow plug in the diesel engines. Hence it would not be wrong to say that questions like ‘how many spark plugs are in a diesel engine’, are irrelevant and stem from common misconceptions among new and misinformed buyers.
Conclusion
In essence it can be said that due to compression air ignition, diesel engines use fuel more efficiently and smoothly. As the entire mixture of the air and fuel is being burnt at the same time, unlike a petrol engine, where ignition starts from a single point and spread through there in the entire cylinder or ignition chamber. Although combustion occurs fast in petrol engines, it is not of same efficiency as the diesel ones.
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To put it simply, it can be said that because of compression air ignition, diesel engines burn fuel more efficiently and smoothly. Since the whole mixture of the air and fuel is all burnt at once—whereas in a petrol engine, ignition is initiated from one point and propagates all through the cylinder—the combustion in diesel engines provides more energy. Even though the combustion in petrol engines takes place quickly, it is not as efficient as in diesel engines.