Here is GMs description of the turbo:

A turbocharger (TC) is a compressor that is used to increase the power output of an engine by increasing the mass of the oxygen and therefore the fuel entering the engine. This BorgWarner™ dual-scroll turbocharger is mounted on the exhaust manifold and the lightweight turbine is driven by the waste energy generated by the flow of the exhaust gases. The turbine is connected by a shaft to the compressor which is mounted in the induction system of the engine. The compressor vanes compress the intake air above atmospheric pressure, thereby greatly increasing the density of the air entering the engine. The turbocharger is capable of producing up to 20 psi or 1.40 bar, of power-enhancing boost.

The TC incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a PWM solenoid, in order to regulate the pressure ratio of the compressor. A charge air bypass valve also controlled by the ECM by utilizing a remotely mounted solenoid is integrated into the unit to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the bypass valve is open during closed throttle deceleration conditions, the bypass valve allows the air to recirculate in the turbocharger and maintain compressor speed. Within a calibrated range during the closed throttle event, or upon a wide open throttle command the bypass valve will then close to optimize turbo response.

The turbocharger is connected to the engine oiling system by a supply and drain tube and Mobil 1™ synthetic oil is installed at the factory. Synthetic oil is required for its friction-reducing capabilities and high-temperature performance. There is a cooling system circuit in the turbocharger that utilizes the engine coolant to further reduce operating temperatures.

During normal operation, if a wide open throttle were to be requested at lower engine speeds, the ECM will command the boost control solenoid with a duty cycle of 100 percent to minimize any turbo lag. During engine loads in the middle and upper RPM ranges, the ECM will command the boost control solenoid, with a duty cycle of 65-80 percent. Manifold pressures of up to 240 kPa are possible.

 

cool thanks for that info

 

The value of "boost" is just a number when considering it stand-alone. That is, there is no easy correlation between the K04 spitting out 18# (if it does) and the Mitsu's T03 spitting out 24#. They're different turbos, and they move different air volumes. You are more likely to be concerned with the CFM a turbo can deliver (ex: a Mitsu [the turbo, not the car] 20g can deliver 2.5-3 times the air flow of the K04, and so could be run at a MUCH lower boost level than the K04 and still deliver more pressurized air to the motor. Now... this is a simplistic example, and you wouldn't want to use the 20g without understanding other implications... one significant one being the incredible lag you'd introduce as you had to spin up the much larger turbine. The topic of "which turbo" to upgrade to is incredibly complex (and it's almost certainly NOT the 20g), but I wanted to clarify the point about boost numbers.

 

i am running a single scroll k-04 on my 01 jetta and apr chip for it they quote 275 tq and 245 hp with a bigger exhaust recommended, i am very impressed with the power the ecotec puts out, my stock boost was 7-10 lb, vw is very conservative, i hit 25 lb in 3 rd gear about 15 in first. i dont have direct injection but even so the ecotec stock almost matches my $3000 plus in mods, i will be looking at the ss panel in the future, very nice ride