injectors?
- Thread starter Andy gt
- Start date
Like Mike ... My answer here is a ... I'm not sure kinda thing
As far as the pcm is concerned ..........
Its about the impedance of the inj's and the inj drivers in the pcm matching
and its a low or high impedance kinda thing.
I wanna say like Mike ... its 50# or maybe 55#
Hey the info is well documented so a search will turn up the accurate info
Grady
S351Saleen77
Member
Like Grady said its High impedence or low impedence. Stock injectors are high imp. A few years ago the biggest high imp I could find were 50lbinj.
Yep, stock injectors are high impedence. They are rated at 11-18 Ohms, while the low impedence injectors are 4-6 Ohms. That is for the Ford Racing versions.
Accel rates them from 12-14 Ohms. They even make a 62 lb injector that is high impedence.
Ford Racing may only go to 50 lbs per hour in their line.
I found some good information about the difference between high and low impedence injectors:
What is the difference between low-impedance and high-impedance injectors?
The important difference between low- and high-impedance injectors is the amount of electric current they require. The high-impedance injectors used by carmakers do not use much current. In fact, even if you connect one directly to your car's battery, it will not draw much juice. This is good for the car maker because the circuit in the ECU that runs the injectors can be a simple switch made from cheap, light-duty components.
A low-impedance injector needs a bunch more electric current to open, about 4 times as much as the high-impedance injector. This is so much current that the injector will burn itself out unless the juice is somehow turned down right after the injector opens. Now, instead of a simple, cheap on/off switch, the ECU must use heavy-duty components that can handle 4 times as much current. The switch must also turn down the flow of electricity after the injector opens so the injector doesn't burn up. This is a much more expensive circuit, and one that generates a bunch more heat inside the computer. Getting rid of that heat raises the computer cost even more.
This business of the ECU yanking the injector open with full current, then turning down the juice to keep it open, is why you hear low impedance injectors called "peak and hold". It takes a big current (the peak) to yank them open, but a much smaller current (the hold) to keep them open.
So why bother with low-impedance injectors if they're harder to run? Because bigger electric currents can yank harder than smaller ones. As the flow rating of an injector increases, so does the weight of whatever the injector uses to turn the fuel on and off (for example, a pintle, or a disk). This is no big deal for stock injectors in the 18 lb/hr to the 30 lb/hr range. Even though they are high-impedance, they're light enough that the small current can yank them open quickly.
But big (like 42 lb/hr and up) high impedance injectors are slow to open. This makes it hard to get a good idle, and kills throttle response. What if you need an injector larger than 42 lb/hr? Simple! You buy low-impedance injectors, which are available up to 160 lb/hr. The large peak current can quickly snap these monster injectors open.
So a low-impedance 50 lb/hr injector will almost certainly be "snappier" than a high-impedance 50 lb/hr injector. When the 50 lb/hr high-impedance injectors on the Acceleronics test car were replaced with 75 lb/hr low-impedance injectors, the ECU setting that adjusts for "sluggishness" had to be set back to stock. The high-impedance 50 lb/hr injectors required much more time to open than stockers, but the low-impedance 75 lb/hr injectors are just as snappy as stockers.
Why can't I run low-impedance injectors with the factory ECU?
Virtually all cars come with high-impedance injectors. The ECU turns high impedance injectors on and off with a simple switch, much like an ordinary light switch. Turn the switch on when you want fuel, turn it off when you don't.
But you can't run low-impedance injectors that way or you will burn them out! These injectors need to be carefully controlled, so a simple on/off switch will not work. They need something more like a dimmer switch. Turn them on all the way to get them to open, then after they open, turn down the dimmer so they don't get too hot.
The second problem is that the ECU's injector drivers can't handle the large electric current needed for low-impedance injectors. Low impedance injectors need about 4 times as much current as high-impedance injectors. This much current will burn out the transistors in the ECU that run the injectors, unless the injectors burn out first!
Accel rates them from 12-14 Ohms. They even make a 62 lb injector that is high impedence.
Ford Racing may only go to 50 lbs per hour in their line.
I found some good information about the difference between high and low impedence injectors:
What is the difference between low-impedance and high-impedance injectors?
The important difference between low- and high-impedance injectors is the amount of electric current they require. The high-impedance injectors used by carmakers do not use much current. In fact, even if you connect one directly to your car's battery, it will not draw much juice. This is good for the car maker because the circuit in the ECU that runs the injectors can be a simple switch made from cheap, light-duty components.
A low-impedance injector needs a bunch more electric current to open, about 4 times as much as the high-impedance injector. This is so much current that the injector will burn itself out unless the juice is somehow turned down right after the injector opens. Now, instead of a simple, cheap on/off switch, the ECU must use heavy-duty components that can handle 4 times as much current. The switch must also turn down the flow of electricity after the injector opens so the injector doesn't burn up. This is a much more expensive circuit, and one that generates a bunch more heat inside the computer. Getting rid of that heat raises the computer cost even more.
This business of the ECU yanking the injector open with full current, then turning down the juice to keep it open, is why you hear low impedance injectors called "peak and hold". It takes a big current (the peak) to yank them open, but a much smaller current (the hold) to keep them open.
So why bother with low-impedance injectors if they're harder to run? Because bigger electric currents can yank harder than smaller ones. As the flow rating of an injector increases, so does the weight of whatever the injector uses to turn the fuel on and off (for example, a pintle, or a disk). This is no big deal for stock injectors in the 18 lb/hr to the 30 lb/hr range. Even though they are high-impedance, they're light enough that the small current can yank them open quickly.
But big (like 42 lb/hr and up) high impedance injectors are slow to open. This makes it hard to get a good idle, and kills throttle response. What if you need an injector larger than 42 lb/hr? Simple! You buy low-impedance injectors, which are available up to 160 lb/hr. The large peak current can quickly snap these monster injectors open.
So a low-impedance 50 lb/hr injector will almost certainly be "snappier" than a high-impedance 50 lb/hr injector. When the 50 lb/hr high-impedance injectors on the Acceleronics test car were replaced with 75 lb/hr low-impedance injectors, the ECU setting that adjusts for "sluggishness" had to be set back to stock. The high-impedance 50 lb/hr injectors required much more time to open than stockers, but the low-impedance 75 lb/hr injectors are just as snappy as stockers.
Why can't I run low-impedance injectors with the factory ECU?
Virtually all cars come with high-impedance injectors. The ECU turns high impedance injectors on and off with a simple switch, much like an ordinary light switch. Turn the switch on when you want fuel, turn it off when you don't.
But you can't run low-impedance injectors that way or you will burn them out! These injectors need to be carefully controlled, so a simple on/off switch will not work. They need something more like a dimmer switch. Turn them on all the way to get them to open, then after they open, turn down the dimmer so they don't get too hot.
The second problem is that the ECU's injector drivers can't handle the large electric current needed for low-impedance injectors. Low impedance injectors need about 4 times as much current as high-impedance injectors. This much current will burn out the transistors in the ECU that run the injectors, unless the injectors burn out first!
fkurls1
Member
Thread merged with prior thread on this topic. The previous thread is helpful and almost necessary in determining what the discussion is about.
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