release engine braking system for a turbocharged internal combustion engine, excessive stress associated with opening the exhaust valves of the engine near top dead center of engine compression strokes when the engine is turning at high speed is prevented by reducing the intake manifold pressure from what it otherwise would be at that high speed. This is done by retarding the turbocharger so that its speed is less than it otherwise would be at high engine speed. This type of retarder is known as compression release engine brake or "Jake brake". A disadvantage of this system is that it becomes very noisy in operation, particularly if the exhaust muffler is faulty; its use is, therefore, banned in some locales. Exhaust brake Exhaust brakes are simpler in operation than an engine brake. Essentially, the exhaust pipe of the vehicle is restricted by a valve. This raises the pressure in the exhaust system, forcing the engine to work harder on the exhaust stroke of its cylinders, so again the engine is acting as an air compressor, with the power required to compress the air being withheld from the exhaust pipe, retarding the vehicle. Turbocharger retarders that restrict the flow of exhaust gas can also help in increasing the exhaust pressure to achieve the same objective. Hydraulic retarder Hydraulic retarders use the viscous drag forces between dynamic and static vanes in a fluid-filled chamber to achieve retardation. There are several different types which can use standard transmission fluid (gear oil), a separate oil supply, water, or a mix of oil and magnetic retardation. Magnetic retarders are similar to the electric retarder discussed below. A simple retarder uses vanes attached to a transmission driveshaft between the clutch and roadwheels. They can also be driven separately via gears off a driveshaft. The vanes are enclosed in a static chamber with small clearances to the chamber's walls (which will also be vaned), as in an automatic transmission. When retardation is required, fluid (oil or water) is pumped into the chamber, and the viscous drag induced will slow the vehicle. The working fluid will heat, and is usually circulated through a cooling system. The degree of retardation can be varied by adjusting the fill level of the chamber. Hydraulic retarders are extremely quiet, often inaudible over the sound of a running engine, and are especially quiet in operation compared to engine brakes. Electric retarder Electric retarders use