It is used when braking and downshifting simultaneously (prior to entering a turn), and allows the driver to "blip" the throttle to raise the engine speed and smoothly engage the lower gear.
As the power band of most race cars is found high in the rev range, this technique can also be used to ensure that engine rpm does not drop below the power band of the car while under braking, by allowing a lower gear to keep the engine in the desired rev range.
This technique ensures that maximum power can be reached the instant the brake pedal is released and the accelerator fully depressed.
When a car with a manual transmission is in motion with the clutch engaged, there is a mechanical connection between the engine and wheels which keeps them in sync with each other.
Therefore, a staple of advanced or professional manual-transmission driving is the "rev match", or "throttle-blip", in which the driver quickly brings the engine up to speed with the wheels by use of the throttle.
Nissan's SynchroRev Match system makes such throttle blipping and advanced techniques by the driver unnecessary and accomplishes engine rev-matching automatically.
Most usefully, if a new, lower gear is selected, the computer will accelerate the engine to the new estimated speed, even to the point of redline.
As the accelerator pedal in such a system has no direct mechanical connection to the throttle valve, the engagement of the system to change engine speeds is apparent to the driver via sound and tachometer cues only, and the feel or weight of the accelerator pedal remains constant.