How To Prevent Serious Damage On A Direct-Injected, Turbocharged Audi Engine
Low-speed pre-ignition is a common yet serious problem for more than one Audi engine, but there are some easy ways to prevent it from happening.
In recent years, pretty much every automaker out there has worked to downsize their engines and add some sort of forced induction – typically, turbos, and in many cases, they also pair them with direct injection systems. The reasoning behind this is simple – this combination produces plenty of power while also improving fuel economy and lowering emissions, which is also important for automakers as they work to adhere to increasingly strict fuel economy and emissions standards. However, this combination has also been known to present its own unique array of issues, and one of the more fatal – at least for this type of Audi engine – is known as low-speed pre-ignition (LSPI), stochastic pre-ignition (SPI), or super-knock.
LSPI is commonly seen in downsized, gas-powered, direct-injected, turbocharged powerplants, which is the case with more than one Audi engine these days. Trouble is, in these smaller, boosted powerplants, high combustion pressures can lead to LSPI, which is essentially uncontrolled combustion that occurs outside of the normal series of events inside something like an Audi engine. This takes place when rising temperature and pressure levels in the cylinder cause unburned fuel to ignite before the spark, leading to engine knock. This occurs at low speeds during a period of instantaneous acceleration.
While detonation occurs after normal combustion, it’s actually less harmful to an engine than LSPI, which happens before, and can lead to some serious damage, as we can see from this 2018 Audi S5 in a recent video from Dave’s Auto Center here, which burned a piston due to LSPI. Trouble is, no one has really been able to figure out the exact cause of this phenomenon, and researchers believe that it may even take place randomly in the combustion chamber.
The most common cause of LSPI, however, are microscopic engine oil droplets, which enter the combustion chamber via the gap between the pistons and the cylinder walls. When that happens, the oil mixes with fuel, gets compressed by the rings, and leads to abnormal combustion. This builds pressure at a rapid rate as well, which can lead to severe engine damage or total failure in some cases. This is precisely why it’s important to recognize the symptoms of knocking – damaged spark plugs, a loss of power, poor fuel economy, a clanging noise when accelerating, or loud noises coming from the engine.
Luckily, there are several ways to prevent LSPI from happening. First, one will want to use a high-quality oil that is also the recommended one for your specific Audi engine as described in the owner’s manual. High-octane fuel can also help, as it’s better equipped to control and resist self-burning, and quality fuel system cleaning products help reduce the risk of low-speed pre-ignition by removing deposits from the fuel system, cleaning it, and restoring engine performance. If nothing else, the small investments you make here can help prevent a major repair – and expense – later on down the road.
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