The turbo resonator is a muffler that slightly reduces the high-pitched noise that comes from the turbocharger, often referred to as turbo whine. It can also change the tone of the noise to make it sound deeper and more appealing. Most turbo resonators are simple, inexpensive and lightweight units that can be quickly installed with a few basic tools. They are often fitted as standard equipment on new turbo-powered vehicles, and can be bought from stores that sell automotive parts. Resonators are made from either plastic, aluminum, stainless steel or carbon fiber. While the plastic models are popular because they are the least expensive, they need to be checked regularly for signs of cracking.
The turbocharger is essentially a jet engine without the combustion stage. It uses the energy of the engine exhaust gases to spin a turbine fan which is connected to a compressor fan. The compressor forces cold air into the engine intake, boosting the air pressure to improve performance. The turbine and compressor blades spins at incredible speeds, usually between ten and twenty thousand revolutions each minute. This produces a loud and high-pitched noise that is undesirable, and may need to be reduced so that the vehicle doesn't exceed noise pollution regulations.
The turbo resonator is a type of straight-through muffler that has a perforated section of pipe surrounded by a sealed outer cylinder, called the resonator chamber. The small perforations cover the entire surface of the inner pipe, and there is a short pipe segment at each end for attaching to the air hoses. The resonator is installed on the air inlet side of the turbocharger, and is not much larger than the section of hose it replaces. The ends of the air hoses are secured to the resonator with hose clips. Unlike the engine muffler, the turbo resonator is not subjected to hot exhaust gases so it can be made of plastic or carbon fiber.
Sound waves travel through the holes in the perforated pipe and are reflected off the wall of the resonator chamber. The turbo resonator is designed so that the reflected waves are exactly out of phase with the original waves. When both waves meet they cancel each other out in a process called destructive interference. It is impossible to eliminate all the noise from the turbocharger because it consists of many different frequencies, so the resonator is designed to remove the frequencies that are responsible for most of the noise. There are some models, called wideband resonators, that can reduce turbo noise across a wide range of frequencies.
Installing a turbo resonator is a simple task that takes less than one hour to perform. However, it may take longer if the turbocharger is in an awkward spot that requires other engine components to be removed and put back again. The resonator can be located anywhere on the air intake hose but is usually placed close to the turbocharger. First, cut out a section of the hose that is a few inches shorter than the resonator. Insert the resonator into the hose ends and secure it with hose clips. Some resonators may have a preferred air flow direction but most will work in any direction. Some models also have a bracket which should be attached to the vehicle framework or engine to help reduce vibration.
The turbo resonator has no moving parts and requires no maintenance. A common problem with plastic models is cracking along the joints caused by engine vibration. Cracks allow intake air to escape and bypass the turbocharger, causing a reduction in engine performance. In some cases, the computer management system interprets this drop in performance as a sign of turbocharger failure, and reduces the performance even further to protect the engine. However, these cracks can be easily fixed with the application of silicon sealant around the joints.