300ZX Twin Turbo Basics

300ZX Twin Turbo Basics: "Words in all capital letters are of key interest and good components for upgrade.
Following the 'air' path through the engine will take us in logical order through all the steps of what the components under the hood are doing. Since this is a twin turbo engine, the process described is happening on both sides of the engine bay. There are several cars like the one that comes from that 'other' Japanese company and starts with an 'S' (and a few might even think was competition for the Z) that use a sequential turbo charging approach, but Nissan chose to use two full range turbos in tandem. (The merits of the two approaches are another discussion.)
Air enters the intake track through the AIR BOX located between the headlights. The air is filtered and sent to the compressor side of the TURBO CHARGER. At this point the turbo can be thought of as two encased paddle wheels linked together with a central shaft. One that uses expanding exhaust gasses to drive the turbine side and the other that takes incoming air and compresses it. Following the laws of thermodynamics, this compressed air has now also become very hot. Cooler intake air produces more horsepower. To cool the intake charge the air is directed through a set of air-to-air INTERCOOLERS. The intercooler acts as a radiator and uses cool outside air passing through it to extract the heat from the hot intake charge. This cool, dense, high pressure air now heads to the intake manifold. Once it reaches the intake manifold (that big aluminum casting on top of the engine) the balance tube equalizes the two air paths. This is just a tube that levels out any pressure differences that may exist between the output of the two turbos and ensures that each of the six cylinders receives the same air flow. The air is then ingested through two intake valves (4 valve per cylinder engine). The usual "internal combustion" process is carried out. The Z has six 370cc INJECTORS for injecting fuel into the combustion chamber, and then a direct ignition coil above each spark plug to ignite the mixture.

Upon leaving the engine via the two exhaust valves the exhaust manifold directs a portion of the exhaust flow through the turbine side of the turbo, and a portion of it is sent to the exhaust system. The turbine side of the turbo eventually dumps its exhaust gasses to the exhaust system also. The job of regulating the exhaust flow either into the turbine or to the exhaust is performed by the WASTEGATE. The wastegate is a simple pneumatic valve that uses a control input from the intake manifold to regulate the pressure that the turbos develop. The key element to horsepower is careful control and management of the boost. Not enough boost and the car "lags", too much and you cook a piston. In conjunction with the "boost", fuel and ignition maps must be in perfect concert. The management of these and other things is the job of the ENGINE MANAGEMENT COMPUTER.

Once in the exhaust system the exhaust gas travels through a set of pre-cats and then through the CATALYTIC CONVERTERS. Once through the cats, the exhaust on a stock set up is sent through a pair of RESONATORS and a balance pipe or "H-PIPE" to even out the exhaust pulses and quiet the tone.

Finally it passes through a pair of MUFFLERS and out the EXHAUST TIPS.

That covers the very basic nature of what is going on under the hood of a 300ZX Twin Turbo."