| The injectors are designed to deliver a metered charge of fuel from a rail that's approximately 45.5psi above manifold pressure. The ECU times the injector pulses based on this basic assumption. If you raise the rail pressure, you'll still hit 100% DC because the ECU doesn't know you changed anything...you'll just run rich all the time. The answer is to use higher-flowing injectors, and reprogram the ECU accordingly. The stock TT uses injectors rated for 370cc/min, and they'll get maxed out around 15-ish psi of boost. Replacing them with 555cc (or 740cc) units allows the ECU to deliver the same fuel charge with a pulse that's 33% (or 50%) shorter than stock. It also means that at 100% duty cycle, they're delivering 1.5x (or 2x) as much fuel as stock, so you can push a lot more boost without overloading the fuel delivery system. The stock pump can support builds of ~700whp...if you go bigger, some guys have been known to run dual stock pumps, others have replaced it with an aftermarket setup.
|
10:08:43 05/11/15
