Why Do Diesel Engines Sound Different?

The blowdown event, which occurs when the exhaust valve opens, causes diesel engines to make additional noise. Because the internal pressure inside the cylinder chamber is often higher in diesel engines than in gasoline engines, the sound produced during blowdown is also higher.

Why do diesels sound like they knock?

What causes diesel engines to make a clatter that is not audible in gasoline engines? — P.S.

The clatter is caused by the engine’s internal burning of diesel fuel. Rather than a spark plug, the fuel in a diesel engine is ignited by high pressure and temperature inside the cylinder.

The clatter is caused by the fuel not burning evenly like it would in a gasoline engine, resulting in a knock. Unlike in a gasoline engine, knock in a diesel engine does not usually pose a threat to the engine. It is simply offensive to the general public.

Because the diesel engine lacks a spark plug and relies solely on the compressive heat inside the cylinder to ignite, the fuel must have excellent ignition characteristics. However, strong ignition quality in any fuel is not always accompanied by good anti-knock capacity. Diesel fuel has a low anti-knock capability since it requires a high igniting capability.

Why are older diesel engines so loud?

Let’s begin with the fundamentals. The high compression ratio of diesel engines is one of the main reasons for their loudness. Diesel engines, as you may know, rely entirely on compression to ignite the fuel. This means that the piston’s press is solely responsible for the igniting of the fuel and the generation of all power.

Whereas a gasoline engine may have a compression ratio of 10:1, a diesel engine has a compression ratio of 15 to 18:1. With such a high level of pressure, an explosion occurs, resulting in a lot more noise. If you’ve ever heard a diesel engine with the exhaust manifold removed, you’ll know that the noise level is far higher than most other engine types.

Because of the almost chaotic compression that causes the diesel fuel to ignite, diesel engines emit that distinctive sound. It’s not as precise as a gasoline engine with ignition and timing.

When the engine is cold and the cylinders aren’t as warm, you’ll hear louder noises. This is due to the fact that they are not sufficiently warm to totally burn the fuel. In order for the engine to reach the temperature required for effective operation, the cylinder walls must warm up and generate heat.

Are diesel engines loud when cold?

Registered. Yes, diesel engines in general, and our design in particular, are louder when cold; try hearing one at -40°C!! Because the gasoline burn propagates more slowly when the cylinder head is cold, it affects timing and causes more diesel “klack.”

Why do diesels knock when cold?

Many diesel engines, however, create an unpleasantly harsh banging sound during cold starts and warm-up at low outside temperatures. A significantly higher cylinder pressure gradient results in a louder and more unpleasant combustion noise under cold running circumstances.

How do you fix a diesel knock?

What is the best way to tell if the engine noises you’re hearing are good or bad? After years of troubleshooting diesels, I’ve discovered that performing a Diesel Purge is the best way to evaluate whether the internal noises you’re hearing are normal or not. Let me explain; with a diesel engine, the majority of the banging and pinging is caused by injector “nailing” and ignition knock. Most of these noises will go away in ten to fifteen minutes if you run diesel purge through your engine. The purge lubricant will lessen “nailing” or hammering in the injectors, while the clean fuel will reduce combustion banging. I often fantasize of being able to run my engine on diesel purging all of the time. The diesel purge is working its way through the pump and injectors, “softening out” all those harsh sounds, and the engine produces such a beautiful sound. (If you put high-quality waste vegetable oil in a diesel engine, the same thing can happen.) If the noise(s) you’ve been worried about disappear during a purge, you can relax. The source of the noises is almost certainly fixable.

In earlier Mercedes diesel engines, the fuel injectors are the source of the most noise. They make ticking, pinging, rattling, and even snapping sounds. This type of injector noise will not do any serious damage to your engine. In most circumstances, diesel purge will silence all injector noises while also softening the knocking noise. If the nailing or banging sounds from your diesel injectors returns after a purge, I propose rebuilding your fuel injectors with the Monark nozzles offered on our website. We provide everything you need, including tools and instructions, to rebuild and pressure balance diesel fuel injectors in your garage.

If, on the other hand, the noise does not go away while the purge is being run through your engine, you should be concerned. You’ll have to look for the source of the noise elsewhere (s). If the deep knock continues, it could be dangerous, and the vehicle should not be driven until the source is identified. See my whole guidebook for additional information on diesel engine noise diagnostics.