Why don't diesel engines use spark plugs for ignition?

[SanAmir]

This is because diesel has a relatively low ignition temperature. Here are the relevant explanations: 1. Introduction: With the motor driving the crankshaft to operate, it drives the engine's crank connecting rod mechanism, valve mechanism, fuel supply mechanism, etc. After intake and compression, the temperature of the compressed air at the end of compression reaches above 700 degrees. At this time, high-pressure diesel is injected into the cylinder in a mist form from the fuel injector, and the formed mixture is immediately ignited, pushing the crankshaft to continue operating. 2. Compression ignition: Diesel engines directly compress the mixture of air and fuel to the ignition point, causing spontaneous ignition, which is called compression ignition. There is no need for an external spark to ignite, so spark plugs are not used. Gasoline engines have a lower compression ratio compared to diesel engines and require ignition to make the gas in the cylinder combust.

[McVanessa]

As a car enthusiast, I find it quite fascinating that diesel engines don't use spark plugs for ignition, relying instead on compressed air to ignite the fuel. Simply put, during diesel engine operation, the piston compresses air to a high-pressure and high-temperature state, reaching temperatures above 500 degrees Celsius. Then, diesel is injected and spontaneously ignites upon contact with the high temperature. Gasoline engines require spark plugs for ignition because gasoline has a higher auto-ignition temperature and needs an external spark to trigger combustion. Diesel, however, has a much lower ignition temperature and can ignite through compression alone. This design brings several benefits, such as higher engine compression ratios, more complete combustion, improved efficiency, and reduced fuel consumption, making it particularly suitable for trucks or SUVs that require high torque. Maintenance is also more hassle-free, unlike gasoline engines where spark plugs are prone to aging or failure and often need replacement. From my experience, diesel engines are a bit noisier, but their simpler and more reliable structure makes them more cost-effective in the long run.

[VonPresley]

Back when I drove trucks, diesel engines never had spark plugs—they relied entirely on compression ignition. The air gets superheated during compression, so diesel fuel ignites automatically when injected into the cylinder, eliminating the need for an ignition system. Gasoline cars, on the other hand, require spark plugs, which can be a hassle. I’ve dealt with issues like carbon buildup or burnt-out spark plugs before. Diesel fuel has different properties, making it easier to self-ignite, and the high compression ratio design boosts efficiency, giving the engine more torque—perfect for climbing hills or hauling heavy loads. Daily maintenance is simpler, costs are lower, and fuel expenses are especially economical for long-distance driving. I think this is a major advantage of diesel engines: simple design yet adaptable to various loads.

[MacKendra]

When studying engines, I found out why diesel engines don't use spark plugs? Because they employ the compression ignition principle. The air is intensely compressed to generate high temperatures, causing the diesel fuel to ignite spontaneously. Gasoline requires spark plugs due to its higher ignition point, where external ignition ensures reliability. Diesel's chemical properties are suited for auto-ignition, with higher compression ratio designs reaching around 15:1, which optimizes the combustion process. The absence of spark plugs reduces failure probabilities and improves efficiency.

[IrisLee]

From a historical perspective, I am fascinated by the idea of Rudolf Diesel, the inventor of the diesel engine, who designed the compression ignition system to eliminate the need for spark plugs. Among the innovations of the late 19th century, this approach relied on compressing air to high temperatures to ignite diesel fuel, replacing the traditional spark-triggered combustion method. The advantages of diesel fuel ignition include improved efficiency, simplified structure, lower maintenance requirements, and better suitability for heavy-duty work compared to gasoline engines. Modern diesel vehicles inherit this principle, resulting in more reliable operation.