Racetronix 57# injectors
01-15-2004, 12:25 PM
#1
Race Car
Thread Starter
Racetronix 57# injectors
http://www.racetronix.com/Racetronix..._Sale-55h.html
Should I have any reservations about upgrading to these? Is a 12 ohm coil going to help me or hurt me? I know I'll run lower current, but are there disadvantages to running a high impedence (is it higher than stock?)?
Should I have any reservations about upgrading to these? Is a 12 ohm coil going to help me or hurt me? I know I'll run lower current, but are there disadvantages to running a high impedence (is it higher than stock?)?
01-15-2004, 03:04 PM
#2
Done With Sidepatch
Rennlist Member
Rennlist Member
Whay are you thinking high impedence? You should be looking at the low impedence injectors (the 3102 model).
http://www.racetronix.com/Racetronix..._Sale-55s.html
Then add resistors and you'll be fine. Some add resistors, some don't. I did as they were inexpensive.
http://www.racetronix.com/Racetronix..._Sale-55s.html
Then add resistors and you'll be fine. Some add resistors, some don't. I did as they were inexpensive.
01-15-2004, 06:24 PM
#5
Race Car
Thread Starter
i just had never seen these and couldn't understand the reason for a 12 ohm coil. I know it would hurt opening response time slightly, but would pull a lot fewer amps. As far as I know the higher impedence injectors tend to be saturated switch and not peak and hold. They can operate that way, it won't hurt them, but the response (opening) is typically slower.
And yes, I do plan on running ballast resistors when I upgrade my injectors as most I've seen are around 2.5 ohm. Good practice to try and run the injectors with the same impedence as stock (for the DME sake).
And yes, I do plan on running ballast resistors when I upgrade my injectors as most I've seen are around 2.5 ohm. Good practice to try and run the injectors with the same impedence as stock (for the DME sake).
01-18-2004, 03:46 AM
#6
Race Director
Remember that flow-rates for injectors are stated for 3.0-bar of fuel-pressure and 100% static duty-cycle (fully open all the time). However, in actual practice, one has to account for actual real-world operating characteristics. Injectors are not digital devices that are either on or off. They have real-world values of mass, current-draw, response-time, heat-generation and rejection, etc. The signal that drives injectors also interacts with all those factors as well. So one has to take all these properties into account when selecting and programming for specific types of injectors.
"i just had never seen these and couldn't understand the reason for a 12 ohm coil. "
They are used for cost-savings and economy. The high-ohm saturated injectors can be built easier and not have to match as high a standard as low-imp. peak & hold injectors. They can also be driven off a simple square wave signal, rather than a peak & hold signal (see below).
"Is a 12 ohm coil going to help me or hurt me?"
Neither really. Here's a picture to help explain the differences.
High-ohm saturated injectors are driven off a simple square-wave signal (cheap electronics). They have response time that's about 3-4x longer than low-ohm peak & hold injectors. At short pulse-width and low duty-cycles, their fuel-delivery can actually be only 1/2 of what the programmed duty-cycle calls for. Also at high-RPM, such as 7000rpm, there's only 16ms for fuel-delivery and even when driven at 100% duty-cycle, with two latency periods per 4-stroke cycle, they will only deliver fuel during 67% of that time.
Low-ohm peak & hold injectors use a more sophisticated signal (costlier electronics), that blasts the injector open quickly using a high-amperage signal ('peak') to accelerate the injector pintle open. Then the current is reduced significantly to just enough to keep the injector open for the rest of the duty-cycle time ('hold').
The two different types of injectors work great when their unique characteristics are used in design parameters for programming the EFI system. The compatibility issue comes in when you swap injectors and driver signals. Such as using high-ohm injectors in a system designed for low-ohm peak & hold injectors.
In this case, the initial high-amperage blast 'peak' opening signal will be 5x HIGHER than the high-ohm injectors were designed for. This can cause overheating, especially at high duty-cycles with insufficient cooling time. Then the 'hold' signal during the rest of the ON period is LOWER than what the high-ohm injectors were expecting as well. So the hold period can result in sporadic and inconsistent fuel-delivery as the injectors flutter between half-open and half-closed. The overal result of using high-ohm injectors in our cars is that the EFi system must be programmed with these conflicts in mind. Such as using a longer duty-cycles for idle to compensate for the longer latency period. Also have to account for the lower fuel-delivery at 100% duty-cycle in the high-end as well.
The net effect is that on our chips, to program for 55# low-impedance injectors, it's simple a scale-back factor of -36.7% to account for the difference in injector sizes (over stock). In the case of 55# high-impedance injectors, the scale-back factor is - 19.8%. So in effect 55# high-ohm injectors have the equivalent flow-rates of a 43# low-ohm injector when used with a peak & hold signal.
"i just had never seen these and couldn't understand the reason for a 12 ohm coil. "
They are used for cost-savings and economy. The high-ohm saturated injectors can be built easier and not have to match as high a standard as low-imp. peak & hold injectors. They can also be driven off a simple square wave signal, rather than a peak & hold signal (see below).
"Is a 12 ohm coil going to help me or hurt me?"
Neither really. Here's a picture to help explain the differences.
High-ohm saturated injectors are driven off a simple square-wave signal (cheap electronics). They have response time that's about 3-4x longer than low-ohm peak & hold injectors. At short pulse-width and low duty-cycles, their fuel-delivery can actually be only 1/2 of what the programmed duty-cycle calls for. Also at high-RPM, such as 7000rpm, there's only 16ms for fuel-delivery and even when driven at 100% duty-cycle, with two latency periods per 4-stroke cycle, they will only deliver fuel during 67% of that time.
Low-ohm peak & hold injectors use a more sophisticated signal (costlier electronics), that blasts the injector open quickly using a high-amperage signal ('peak') to accelerate the injector pintle open. Then the current is reduced significantly to just enough to keep the injector open for the rest of the duty-cycle time ('hold').
The two different types of injectors work great when their unique characteristics are used in design parameters for programming the EFI system. The compatibility issue comes in when you swap injectors and driver signals. Such as using high-ohm injectors in a system designed for low-ohm peak & hold injectors.
In this case, the initial high-amperage blast 'peak' opening signal will be 5x HIGHER than the high-ohm injectors were designed for. This can cause overheating, especially at high duty-cycles with insufficient cooling time. Then the 'hold' signal during the rest of the ON period is LOWER than what the high-ohm injectors were expecting as well. So the hold period can result in sporadic and inconsistent fuel-delivery as the injectors flutter between half-open and half-closed. The overal result of using high-ohm injectors in our cars is that the EFi system must be programmed with these conflicts in mind. Such as using a longer duty-cycles for idle to compensate for the longer latency period. Also have to account for the lower fuel-delivery at 100% duty-cycle in the high-end as well.
The net effect is that on our chips, to program for 55# low-impedance injectors, it's simple a scale-back factor of -36.7% to account for the difference in injector sizes (over stock). In the case of 55# high-impedance injectors, the scale-back factor is - 19.8%. So in effect 55# high-ohm injectors have the equivalent flow-rates of a 43# low-ohm injector when used with a peak & hold signal.
