Changing from High imp to low imp injectors
Changing from High imp to low imp injectors
(OP)
Hello all,
I'm going to have to change the petrol injectors on my car for some bigger ones due to a power increase, the problem is my car runs High impedance/high resistance injectors and the only ones I can find to replace them are low impedance ones and these will not work with my existing system. I have heard that you can upgrade your system by the fitting of 'ballast resistors' in the injector wiring.
Does anyone have any idea if this is possible and if it is, exactly how this can be done?
Thanks.
I'm going to have to change the petrol injectors on my car for some bigger ones due to a power increase, the problem is my car runs High impedance/high resistance injectors and the only ones I can find to replace them are low impedance ones and these will not work with my existing system. I have heard that you can upgrade your system by the fitting of 'ballast resistors' in the injector wiring.
Does anyone have any idea if this is possible and if it is, exactly how this can be done?
Thanks.





RE: Changing from High imp to low imp injectors
Add the appropriate ballast resistor so that the system impedance is the same with the low impedance injector as your original injector. Just make sure the ballast resistor is rated for the power you will be using.
Reidh
RE: Changing from High imp to low imp injectors
The original high imp injectors are 14.5 ohm and the new ones are .5 ohm.
Also, the original injectors (supplied with the car from the factory) are rated at 6 - 16vdc.
Soooo:
I will need a resistor of 14 ohm which will handle 16 volts right? Presumably I can go some way over this voltage, but by how much? 24v be ok?
Also presumably the resistor will need placing in the +tive side of the injector drive wiring and one per injector?
Sorry for all my questions, but thanks for the reply!
RE: Changing from High imp to low imp injectors
"Just make sure the ballast resistor is rated for the power you will be using."
So a 14 ohm, 1/4-watt resistor is probably not going to work for very long. I think you may also want to spend a little time thinking about how (and perhaps where) you're going to dump the heat that a resistor of adequate power rating will generate, though.
Norm
RE: Changing from High imp to low imp injectors
RE: Changing from High imp to low imp injectors
RE: Changing from High imp to low imp injectors
.5 ohm does sound low for an injector. You may want to double check that.
Reidh
RE: Changing from High imp to low imp injectors
looking to use cc or lbs per hour
RE: Changing from High imp to low imp injectors
You need to determine current requirements of the injectors, and current drive capability of your ECU. If its not adequate, a peak hold circuit like dgallup suggested might be worth investigating. Or just find better suited injectors.
RE: Changing from High imp to low imp injectors
First of all thanks for all your replies - makes interesting reading.
Things have moved on a bit since my initial ideas/post on the subject and I have learned more, some inline with your ideas, some not, i'll pass it on regardless...
The car is a modified 4 cylinder 2 ltr turbo motor and I'm hoping for 350bhp max when the ECU is remapped.
The injectors I had in mind were Bosch 0 280 150 403 'Greys' Picked because they should supply enough fuel for the power output expected and are readily available here in the UK. The resistance I was quoted was indeed wrong, they are 2.5 ohm I borrowed one and checked it with my tester.
The idea of using seperate resistors in series will cause injector lag so no good. Apparently you can get a separate peak-and-hold injector driver box for these type of applications which would work better.
Even better again of course is to use the correct resistance injectors in the first place so I am searching for an injector of standard Bosch motorsport style/size, which will supply enough fuel for my power output, I am suggesting a 550 cc High imp saturated injector.
Any help/ideas welcome.
Thanks.
RE: Changing from High imp to low imp injectors
Depending on what you are looking for, there might even be some factory injectors are large enough to meet your goals.
RE: Changing from High imp to low imp injectors
RE: Changing from High imp to low imp injectors
Not true if you use 6 ohm resistors. Many vehicles used to come from the factory that way back when high impedance injectors were strictly low flow weaklings. I have measured the better dynamic range with a ballasted drive setup than a peak & hold driver or high impedance injectors.
RE: Changing from High imp to low imp injectors
is poor and influenced buy voltage change,injector offset
is also difficault to set accurately and as a consequence
when using large injectors at low duty cycles it becomes
a balancing act to keep it in tune over any peroid of time.
Despit compensation tables in the ECU.