The Turbo Boost
The reason for this being a very efficient way of raising the power of the engine is that when the exhaust gases make the turbo spin faster and press more air into the engine, more exhaust gases are created, which makes the turbo spin faster, and so on... This continues until the desired pressure is reached. At this point a control valve (the waste gate) opens, and releases the excess pressure to keep it at the desired level. By replacing the waste gate, we are able to increase the level at which it opens and thereby get more power from the engine.

Another common way to increase the boost is to connect a T-connection to the waste gate, and by letting air into the connection increase the pressure. This is a cheaper, but not as good solution, since it requires the pressure being manually adjusted. This also increases the risk for so called "boost-knocks"

Exhaust system
The next thing you need to do something about is the exhaust system. The stock mounted system is too small to handle the extra exhaust gases that are produced when increasing the turbo pressure. An exhaust system of 2.5" should be enough for just above than 300 bhp. If you plan for even more power, a 3" system might be required. Most sport exhaust systems often stretch from the cat (catalytic converter) and back, but you might want to give the whole system some thought. A 3" front pipe down to the cat and a race cat prevents any restrictions in the system. A new, bigger exhaust system also gives a more powerful sound, and helps the looks of the vehicle.

Air filter
When we're thinking of replacing the exhaust system, we might consider replacing the air filter as well. There are several solutions. Either, you go all the way and buy an open sport filter, that also adds to the sound experience. The option is to cut open the stock mounted air filter box. The first alternative is recommended. To make sure that cold air finds it's way to the filter, one should also connect a flexible hose from the air intake in the front, the same place as the original air filter box draws it's air from, to where the new filter is fitted.

Chip
The next step would be to replace the EPROM chip that controls the ignition timing. The chip is fitted in the engine control box, mounted behind the panel in front of the passenger door. The chip is soldered in place though, and you have to fully remove it to be able to replace it with another chip. Many people believe that an otherwise stock equipped car will get a 30-40 bhp increase by only replacing the chip. This is, however, unfortunately not the case. On a 200SX, the replacement chip removes the turbo pressure restriction. The chip also controls the amount of fuel distributed to the engine, and the ignition timing.

Intercooler
The downside with a turbo is that the air that is pushed into the engine gets hot. This decreases the power, as the molecules take up more space when they are hot and move faster. Worst case is if the air gets so hot that it damages the engine. An intercooler is mounted between the turbo and the engine, and cools the air just like a regular radiator. There is a stock mounted intercooler on the 200SX, although it's very small and situated in a badly chosen place in front of the left front wheel. You should consider replacing it with a larger one, mounted in front of the radiator. If you change location, you can fit one that's approximately 4-5 times larger, which makes the air we let into the engine considerably cooler.

If you think this seems too expensive or too large an operation, there are replacement intercoolers that mounts in the stock location, and are much more efficient than the stock unit.

Turbo
After making sure the air flowing into the engine is cold enough, it's time to replace the turbo charger. The choice of unit depends totally on how much power you're planning for in your car. The most common alternatives are an upgraded version of the stock turbo T25, a T28 from Nissan Sunny GTi-R, a T3 that among other cars are installed in Ford Sierra Cosworth, a T04, or a Mitsubishi turbo. Regardless of which of these you choose, you get a turbo that can deliver much higher pressure, and not heating the air as much at all as the stock T25 unit. T28 can in its most modified version deliver 350bhp, as the T3 in its most modified version is capable of up to impressive 450bhp.

Fuel Injection
For powers above 250 bhp, you should also give the fuel injection a good look. Neither the fuel pump, nor the stock mounted injectors will be able to deliver enough fuel. The alternative is to totally replace the fuel pump and injectors for more efficient ones. Also, the air mass meter might require some improvement. Either you can have it widened, or you can buy a bigger one.

Camshafts
Turbo engines are often equipped with "gentle" cams, that is cams with short duration. This is because the power in high revs, where the turbo comes in effect, is quite enough. Instead they optimize the cams to increase the power in low revs. Of course you can also replace the cams with ones optimized for better performance at higher revs.

Water injection, cooling the intercooler
Water injection prevents knocking, and enables you to use a higher turbo pressure. It works by injecting a fine spray of water, most often before the turbo charger. Inside the cylinder, the water becomes steam, and this steam consumes heat.

By fitting a nozzle that ejects fine spread water onto the intercooler, the cooling capacity can be increased with 25-30%.

Miscellaneous
If you've increased the power of your car, you might also want to give the brakes and road handling a thought. Brake discs and calipers are available in many sizes and makes. The road handling is improved by fitting new dampers and harder springs. The car itself can also be stiffened, thus kept from flexing, by fitting ???strut bars??? and bigger anti roll bars front and rear.