The N75 is the VW/Audi 1.8T
part identification number for the wastegate by-pass
regulator valve. This valve is responsible for controlling the movement of the
pneumatic actuator which drives the wastegate. The wastegate is an internal
valve in the turbo-charger which controls the amount of exhaust gas that flows
over the turbo impeller generating boost. Under normal operating conditions the
engine's ECU sends signals to the N75 valve asking it to open or close which
adds or reduces pressure on the wastegate actuator which results in more or less
boost. The N75 valve J-valve modifies the normal operating parameters of the
original N75 valve by delaying the speed at which these ECU signals are
interpreted. The result is a higher initial peak boost and an elevated boost
curve which tapers back to stock/chipped levels over the engines rev range.
Average boost gains are 1-3psi over the rev band.