Causes Of Engine Knock In German Performance Cars
You have paid a pretty penny for that high-powered German automobile. You want good performance as a reward for the investment, and ordinarily an owner of a German car is not disappointed. However, there are some problems that these uber-performance vehicles can experience which can be quite serious. Engine knock ranks high on the list.
What It Is?
The fuel combination of the car is extremely important within the engine. If the combination of air and fuel is off-balance the fuel does not burn properly. The pockets of fuel will not combust as they are supposed to, and that can result in shock waves that can damage not only the cylinder wall of the engine, but also the piston. It generates the little pinging sound that lets a driver know a knock exists.
There are several causes of knock and one of them is having the wrong spark plugs. A spark plug will have a heat range noted in its part number, and that is the boundary within which the spark plug operates. Spark plugs that are working outside of the range can be a cause of that pinging sound. It is quite possible that the octane rating of the fuel being used is not sufficient. The German high-performance car is going to require a specific rating on the octane or AKI (anti-knock index) for top performance. A low AKI is going to bring on knock. American gasoline must have a specified amount of carbon cleaning detergent as ingredient, but there may still be deposits of carbon on the cylinder walls. A large accumulation of carbon is going to increase compression and create knock as a consequence. Some other causes may include defects in the main crankshaft, a water pump bearing that has become worn out, and the timing belt tensioner may have become loose.
German Car Difference
Knock in a Mercedes that has a diesel engine can be an entirely different story. The sound comes from air compressing in the cylinders along with the ignition of the fuel being injected. Whereas in a gasoline engine the fuel mixes with the air and then is compressed prior to ignition, only the air is compressed in a diesel engine. It is possible that in a diesel the knock is not considered a major difficulty. It may even be viewed as a sign of fuel efficiency. Knock would only become a concern if it is severe. A BMW model has a knock sensor in the engine to detect the knock, and slow the ignition spark until the knock is no longer heard. An Audi may experience knock because the motor oil used is of poor quality. These high-performance cars clearly have different sources for the knock condition.
What to Do?
The textbook solution to the knock problem is to change the type of gasoline used in the car, and perhaps take a look at spark plugs. The BMW has the knock sensor and that means the automobile can handle the problem all by itself. In the Mercedes knock may be the price for better fuel efficiency, but the car should be looked at as the sound gets louder. The Audi apparently just requires a different grade of motor oil and premium level fuel.
Still, these high-performance cars and their state-of-the-art technology can’t be taken for granted. Rather than worry about a persistent sound a maintenance appointment needs to be made. This is where the owner has to be careful. Not every auto mechanic is trained to service a Mercedes or an Audi. Taking the car into an ordinary automotive service center can result in the wrong type of work being done on these models. It is critical that only auto mechanic who has certified expertise be allowed to inspect the cause of the pinging sound. The risk of the wrong maintenance can ultimately be calculated in dollars and cents; lots of each.
German high-performance cars can be a very substantial investment. The owner has to consider that anything which harms performance is going to lower the rate of return on that investment. Asking the auto mechanic to check on pinging sound can be a standard part of any maintenance checkup. The good news is that it may be coming from someplace other than the engine.