Holley is now offering Terminator X high-impedance fuel injectors rated at a healthy 220 lb/hr, but at a more affordable price than the market has presented in the past. Such a bargain, however, should not be looked at as an open invitation to rush out and modify your EFI system. There are critical factors to consider before adding that much fuel-delivery capacity to a performance engine.
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With a 220 lb/hr rating (at 43 PSI base fuel pressure), this injector is well suited for V8 engines making upwards of 2,500 horsepower on gasoline. Since engines running methanol or E85 require significant more fuel delivery, the suggested maximum horsepower drops to around 1,800 horsepower for E85 and even less for methanol—given the number of variables that come into play with that fuel.
“These injectors are for any application where the user has run out of fuel injector for their combo and needs more fuel to support their engine,” says Holley engineer Matthew Lunsford. “Especially high-consumption fuels like E85.”
The new Terminator X injector is designed for performance enthusiasts and racers using an electronic control unit (ECU) with a saturated driver. The ECUs found in factory production vehicles often have saturated drivers designed to work with high-impedance injectors. The ECUs in Holley’s lineup that work with high-impedance injectors include the Terminator X, HP and Dominator.
Holley’s high-impedance injectors are not to be used with ECUs designed for low-impedance, also known as peak-and-hold injectors. The difference between high- and low-impedance injectors is the ohm, or resistance, reading across the injector coil windings. Low-impedance injectors typically measure four ohms or less while high-impedance injectors are eight ohms or more.
The peak-and-hold injector requires a more complex signal to operate. A strong initial current opens the injector quickly, then a low secondary current is introduced to keep it open until the end of the pulse. This low current also allows the injector to close more quickly than if the stronger current were maintained. With a saturated injector, the signal is consistent for opening and closing the injector.
When the popularity of fuel injection with performance enthusiasts grew in the 1980s and early 1990s, low-impedance injectors were preferred for high-horsepower applications because fuel delivery was more reliable. Today, however, with improved designs, materials and tighter manufacturing tolerances, the high-impedance injector has matched its brother in quality, performance and fuel flow.
“There’s really no specific advantage between the two,” confirms Lunsford. “A low-impedance injector driver normally has more amperage capability and costs more. So, the high-impedance injectors started becoming popular with OEM computers that don’t have robust injector drivers. As of now, for most applications the injector type is dictated by the ECU that it’s being run on and the flow rate at which the customer needs.”
While the Holley Terminator X and X Max ECUs require high-impedance injectors, the HP and Dominator ECUs can support high- or low-impedance injectors.
“An injector driver may say ‘8:2,’ which means it can peak output of 8 amps to get the injector pintle motivated and …….