//scottInSoCal

Two questions:

1)What is the highest psi/bar that is being run on an S4

2)At what boost level does it become necessary to upgrade the fuel system?

Thanks in advance for any replies.

Ferris TMK

The ECU uses the MAPS to dump fuel at WOT. If there is more pressure then the ECU knows about, you'll run rich.. So the first step reprogramming the ECU to accomidate the fuel system.. Also since we use rising rate fuel pressure regulators, the pressure on the injector rails will be adjusted along with the boost..

//scottInSoCal

right, but is there a boost level at which the fuel system can not accomidate (ie, the pressure demand is too high)? For instance, if the turbos were upgraded to put out 21 psi, would it be necessary to replace the fuel pump and/or the injectors?

Ferris TMK

I wish I had all the data, but from what I remember the injectors become a problem before fuel system pressure does. Since the fuel system increase pressure from the base line of 4 bar once your in boost the real restriction is how much the injectors could flow. I suppose if you run some astronmical amount of boost the pump may not be able to keep up, but I'd need to find out the pump data again to tell you what that number is.

Point is the injectors will be the restriction WAY before the pressure of the system. With out the CC's of the injectors I can't give you exact numbers...

//scottInSoCal

Thanks for the help!