Originally Posted by Stewi
yeah the only time you need secondary injectors is for high HP/high boost applications. example, RX7's are notorious for running secondary injectors. What happens is you have your regular 4 injectors, in vacuum and low boost the 4 injectors give enough fuel, once the car starts boosting higher, the secondary injectors are activated to add more fuel with the extra boost. I know of 2 people with EVO's doing the same thing, they run 2 seperate fuel rails, a walbro 255 pump in the tank, and 2 walbro inline pumps (one to feed each rail), 8, 720cc injectors. 4 of the injectors are on all the time and the other 4 only turn on after 20psi of boost.