Hey guys,

What voltage and amperage are used to fire an injector?

Thanks:hail: :hail: :hail:

 

It all depends what type of vehicle we are talking about. There are low impedance and high impedance injectors. Impedance is similar to resistance, only it is measured at the normal operating frequency range of the device being measured. some injectors are low impedance, they are called "peak-and-hold". An example I can think of for a low impedance is a Buick Grand National, there are many others but I dont know them off the top of my head. "Peak and hold" means that a little more voltage is given at the very beginning of a pulse and then it is lowered to keep the current down just to get the injector "kicked" open then a little is used to hold it open. High impedance injectors are mearly applied voltage and held that way, they are also known as "saturation" style injectors. The third gen camaros and firebirds all use high impedance "saturation" style injectors. I believe the high impedance like ours simply use 12 volts from the fuse panel/injector bank circuit (A side and B side) and ground is applied/released from the driver circuit. As for peak and hold they use the same 12 volts but it is lowered to a much lower voltage in a fraction of a second. Puting low impedance injectors into a high impedance injector's plug/spot can result in the driver circuit burning up very quickly, somtimes almost instantaniously. The driver circuit as I understand it is similar to a very fast "on demand of the computer" relay circuit. It is an "amplifier" type circuit in design, and unless this "amplifier circuit is designed for both type injectors (like some aftermarket ECM's are) It can burn up if you try to run low in a high's spot. On a lighter note, In most cases, thank goodness for us-our Ford bretheren use this type of high impedance injector also. although the fords normal operating pressure is about 5 psi lower than ours on the fuel rail, their injectors (almost all injectors) are rated for flow at the same PSI as ours are. What this means is that instead of having to buy very expensive aftermarket injectors to up size or to just replace worn out ones, we can just get the very affordable ford units all the way up to 36 or 38 psi (its one or the other I cant remember which the new lightning uses. These injectors (despite the best efforts of the manufacturer on its other product's) are actually very good in quality, and flow ratings from injector to injector are very close for a mass produced item. They employ modern anti clogging technology (something our early TPI rochester injectors didnt) and they have a very high pressure threshold meaning where some aftermarket injectors fail to open when faced with the high fuel pressures of a dry manifold nitrous shot or high pressure from an FMU at full boost the fords seem to keep opening. As you could guess a injector that is locked closed due to the high pressures, at such a critical time of nitrous activation (dry manifold) or full boost could be detrimental.

 

love all that info,

Thank you!!!:hail: :hail: :hail: :hail: :hail: :hail:

 

First, knock it off with the :hail: :hail: :hail: :hail: :hail: :hail: unless somebody actually does something REALLY worth praising them for (It’s in every one of your questions and it’s almost enough for me to consider not answering), it’s annoying.

A couple of details to add to b4c’s:
- ford lightning injectors are 42# injectors and have replaced the svo/motorsport 36’s, for the most part in ford ‘performance’ applications V8’s all got high impedance injectors and the supercharged and turbocharged 6’s and 4’s got low impedance.
- Low impedance injector drivers _are supposed to_ have a current limiter that does not allow them to draw as much current as they would like based on their low impedance (the lower the impedance the more current something will draw if it is allowed to), and what it is really supposed to do is after the initial injector opening, the current is supposed to be limited to a fraction of an amp, just enough to keep the injector open. This is supposed to keep the high impedance injectors from burning themselves up. In practice, it seems that most ‘low impedance drivers’ are just injector drivers wired to supply more current without melting their own electronics. I suspect that this works real world since we don’t drive around at WOT all the time, but it should limit injector life.
- a low impedance (peak and hold) driver will work fine with a high impedance injector but not vice versa (well, not for long, in theory you should be having a contest which will burn up faster, the injectors or the injector drivers). The exception to this appears to be the GM 749 (Sy/Ty/Sunbird) ECM which used high Z(the symbol for impedance) injectors in the Sy/Ty’s and low Z injectors in the sunbird and from what I believe is just a normal high Z driver. I don’t think it would work for long with 8 low Z injectors even though it was fine with 4.