Originally Posted by RCEngineering

Peak and hold injectors are fired at 4 to 6 Amps, through a ballast resistor, and then fold back to 1 - 2 Amps for the duration of the injection event. They are also known as "fold back" Injectors. Peak and hold injectors are faster responding than Saturated injectors by as much as 1 to 1.5 Ms. They are activated with more power at opening than the saturated types (4-6 Amps vs. .75 -1 Amp.). Peak and hold injectors will maintain injection delivery, cycle to cycle, continuity more accurately than the saturated type. This is particularly true and even more important in high-pressure (75 - 100+ PSI) systems. The higher Hydrostatic loading at excitation requires more amperage to initially activate the injector solenoid and properly maintain complete opening. Peak and hold systems are more expensive to manufacture because they require one computer "injector driver" per injector in most applications. This is a design requirement in Sequential Fire Systems where each injector is fired at a very precise, pre determined, time in the 720 degree 4 stroke processes. P&H injectors are also wound with copper wire instead of brass wire. Early 7M-GTE used Type E - P&H rail feed style up through 1992 and then changed to Type E, galley Feed units for the 2JZ/GTE Toyota lists and rates all of their injectors in cc/Per Minute at different pressures, 36.4 PSI. & 41.2. PSI.---- 7M-GTE injectors are listed at 430 cc Per/Min. at 42.1 PSI. and the 2JZ/GTE are rated at 540 cc/Min.

Saturated injectors are used in almost all-standard production, 1998, engines because of the system cost and simplicity. Saturated based systems usually fire all injectors at the same time, once every rotation discharging half of the required fuel per cycle at each event. Some systems fire half of the injectors at one time and the other half at a different time. These systems are called "Batch Fire" and "Semi-Batch Fire " respectively. This system is used in 90 % of all general production engines (cost and simplicity). In almost every case Manufactures will only use Peak and hold injectors in High Performance applications or in Turbo applications. This is true in the Ford/Mazda family, Chrysler/Mitsubishi family, Nissan Group and the Honda/Acura folks as of 1997. General Motors/Toyota cars are also in this same family. OEM APPLICATIONS GM uses Saturated Rochester injectors in everything but some of the High performance cars, hear they use Lucas Injectors, and in the turbo trucks they use Bosch. Toyota uses saturated injectors in everything but its turbo models - all Nippon-Denso. Honda, last year changed all but the NSX to saturated, most all of Keihin make with some IPT. Nissan uses saturated units only, as of this year, Jecs or Hitachi manufactures. Chrysler/Mitsubishi - same deal - all but the turbos are saturated, Siemens or Bendix make. Ford uses Bosch or Nippon-Denso depending on the Model. All are Sat. except Turbo Models. Bosch and Lucas injectors are used in VWs.. BMW , Bosch up until this year, now Lucas --- European cars use an assortment of injectors including Weber, Bosch and Lucas.

RC