Draft:Quad-Turbo

Quad-turbo refers to an engine made up of four turbochargers work in tandem to compress intake air for a direct-injection engine. The most common layout features four identical turbocharges in series, each processing half of a V engine's or a W engine's produced exhaust through dependent pipes. The four turbochargers must be matching.

Types and combinations
There are only two turbine setups used for quad-turbo setups:


 * Sequential
 * Series

These can be applied to any of the three types of compressor setups.


 * Compound Compressors
 * Staged Compound Compressors
 * Staged Sequential Compressors

Sequential
Sequential turbocharging refers to a set-up in which the engine relies on one turbo for lower engine speeds, and a second or all four turbocharges are relied on to build up higher engine speeds. This system intends to overcome the limitation of large turbocharges to not provide sufficient boost at low RPM. Small turbochargers, on the other hand, are effective at a low RPM but can provide the quantity of compressed intake gases required at a higher RPM. Therefore, sequential turbocharger systems provide a way to increase turbo lag without compromising power output at high RPM.

The system is arranged so that a small ("primary") turbocharger is active while the engine is operating at low RPM, which reduces the boost threshold (RPM at which effective boost is provided) and turbo lag. As RPM increases, a small amount of exhaust gas is fed to the larger ("secondary") turbocharger, to bring it up to operating speed. Then at high RPM, all of the exhaust gases are directed to the secondary turbocharger, so that it can provide the boost required by the engine at high RPM. The four turbochargers at once provide what is called a ("quaternary") turbocharger to access the exhaust pipe to release the flow of the energy of the speed once the RPM hits its limiter,

The first production car to access sequential turbocharged quad-turbo was the 1999-2002 Nissan Skyline GT-R which used sequential quad-turbos on its RB34 engine.Turbocharger

Series
A serial turbocharger is where the turbochargers are connected in series with the output of the first two turbochargers then being further compressed by the second two turbochargers and in some cases powering the larger turbine.

A sequential turbo can also be to a system where the input pressure must be greater than can be provided by a twin-turbo, commonly called a compound quad-turbo system. In this case, multiple similarly sized turbocharged are used in sequence but constantly operating. The first twin-turbo boosts provide the initial compression. Subsequent twin-turbos put out the charge from the previous stage and compress it further.