when i bought my injectors i had the option of buying them for high impedance or low impedance ...........not knowing the difference at the time i just went with low....... so later on i compared my old injectors to my new ones i found that the old 2004 injectors were high impedance i think 22ohms while the new 780cc injectors i bought were 2.2ohms i was talking to some techs in my class and they mentioned some possible problems if switching from low impedance to high impedance could have possible negative effects on the pcm could this be true for the opposite?
__________________
agp gt40
with some supporting stuff
stock exhaust no cat
277 hp 263tq @ 15 psi untuned
Ouch, you NEED high impedance injectors. DO NOT put the injectors you got into the car. If you put the low impedance injectors in the car you will most likely damage the injector drivers in the PCM, as they were never designed for such a high current.
One "option" (you see cheapo honda guys do this alot) is to wire in 10 Ohm (high wattage) resistors inline with the injectors you bought to effectively increase the impedance. This will at least save your PCM, however it really isnt a great idea because the injectors you bought were DESIGNED to be run by a low impedance injector driver, and the injectors will open MUCH slower than they are supposed to.
My personal suggestion is to return what you got, or sell it, and pick up the correct high impedance injectors.
They will work if you get some injector resistors from a turbo DSM.
Are you sure of this? First off we have no plug to plug in the DSM injector box, and I also believe (correct me if I am wrong) the injector box ohms out somewhere near 6 OHMs a resistor which is still pretty low. Not to mention, like I said before, you are defeating the purpose of the low impedance injectors by wiring in resistors to increase the impedance, in fact you are making them function worse than their high Z counterparts which were designed to run as high impedance injectors.
maybe i can get a second opinion on installing additional resistors in-line to increase the resistance so that i won't mess up the injector drivers, i know that installing 2x10ohm resistors will work but im alittle puzzled on the delay in the injector firing time i just don't see how that will will be affected by bringing up the resistance to its proper level wether the resistance is in the injector or elsewhere in the wire connector should be the same... anybody? and just to mention the car has been running fine without any mishap for now, maybe 2-3 minutes total(the car has been sitting in the shop.)
Injector resistors do not damage anything or slow the injectors down. Stock ECU uses a "saturated" injector firing scheme which just provides a ground path for the injector for the entire duration of the pulse width. This fine on a high impedance injector because the current flow is rather low. On a low-Z injector current would be very high, which is why they are considered "peak and hold". On a peak and hold setup the ECU will provide ground path for small duration of the pulse width to open the injector then pulse width modulate the ground path to cut the current level to keep the injector open.
So, as long as you add a resistor inline with the injector you can hold it open with a saturated driver as the resistor takes all the load. The performance will not decrease. The factory DSM uses a saturated driver with a low-Z injector and there are no issues.
maybe i can get a second opinion on installing additional resistors in-line to increase the resistance so that i won't mess up the injector drivers
- a little puzzled on the delay in the injector firing time i just don't see how that will will be affected by bringing up the resistance to its proper level wether the resistance is in the injector or elsewhere in the wire connector should be the same...
The NGC controller isn't damaged by excessive current on the injector drivers, though the drivers could shut off in the interest of self preservation. The stock injectors are about 12 ohms. Adding a 10 ohm resistor brings the peak/holds up to the right ballpark area for the NGC's driver circuits. Just like our prior SBECs, the only thing that the NGC is looking for is a greater than 60 volt spike on the injector circuit upon field collapse. That's pretty much the only thing that's being monitored as far as setting injector faults.
The reason that the opening time is delayed ("slowed down") is the change in time it takes for the magnetic field to build before it's strong enough to pull the injector open. A peak-hold injector opens with an initial spike of 6 amps or so (which is then effectively lowered by PWM on the ground to a lower level that is sufficient to hold it open - hence the name Peak/Hold).
A saturation injector's magnetic field builds slower due to a lower amperage of around .8-1 amp. Peak holds generally have fewer windings of a larger gauge wire than saturation injectors (and subsequently lower resistance). When you apply lower current levels (up to 600% lower in this case of 6 vs. 1 amp) to a peak/hold, you weaken the strength of the magnetic field and very likely increase the amount of time it takes for the magnetic field to build enough strength to open the injector. Peak/hold injectors were made to be slammed open with about 6 amps, not 1. They'll still open, but the fewer windings don't develop as much pull at lower amperage and may take slightly longer than the saturation injectors to open. Does it really make a power difference? Probably not a very significant one IMO.
thanks alot for everyones input ive gotten a good understanding of what you mean but when i measured the resistance from the 2004 injector it was reading at 22ohms.. ill double check it again ill post in a couple of seconds.
yeah i just checked the stock injector was reading 11.5ohms cold and my new injectors are reading at 2ohms. so with the magnetic field collapes in mind the injector drivers should be able to withstand the extra current ? or does that only apply to the voltage so
old injectors 12 v /12ohm = 1 amps
new injectors 12 v / 2ohm = 6 amps ( with 6 amps running threw the drivers something has to short.. i mean i don't think the wire gauge can handle that...
sorry if i sound noob in electrical its because i am lol ...
Injector resistors do not damage anything or slow the injectors down. Stock ECU uses a "saturated" injector firing scheme which just provides a ground path for the injector for the entire duration of the pulse width. This fine on a high impedance injector because the current flow is rather low. On a low-Z injector current would be very high, which is why they are considered "peak and hold". On a peak and hold setup the ECU will provide ground path for small duration of the pulse width to open the injector then pulse width modulate the ground path to cut the current level to keep the injector open.
So, as long as you add a resistor inline with the injector you can hold it open with a saturated driver as the resistor takes all the load. The performance will not decrease. The factory DSM uses a saturated driver with a low-Z injector and there are no issues.
Read exactly what CCH posted. Just like he said, it definately slows down the injector opening time. That is exactly why most high performance, hi-revving, systems all use low impedance injectors. Because the large surge of inital current helps to open energize the coil/magnetics to slam the injector open.
new injectors 12 v / 2ohm = 6 amps ( with 6 amps running threw the drivers something has to short.. i mean i don't think the wire gauge can handle that...
sorry if i sound noob in electrical its because i am lol ...
LOL Pyrox, you're not too bad of a noob if you've already got a handle on Ohm's Law (kudos to you). I taught a lot of electrical one and two classes for Chrysler back when I was an instructor and there were always a few people in every class who had been doing it for years and didn't have a handle on it.
Your statement above is exactly why you'd need the additional resistors in series with the low impedance injectors - decrease the current in the circuit to protect the driver circuits - as for the wiring, the gauge would handle a 6 amp load OK. (I'm looking at 8W30 in an '05 service manual and we're showing the wires at 16 gauge). It's mostly a case of trying not to overwork the driver circuits.
I ran 10 ohm resistors on my 880cc low impedance injectors for many months daily driving at 574whp. I do however also recommend getting the correct injector...or buying an EMS.
I tested high vs low-Z injectors on the scope. The difference was VERY minimal... we're talking maybe .001ms. As long as you maintain a good flat air/fuel ratio what difference does it make. You do know sequential injection goes out the window at higher duty cycles. You're spraying at a closed valve anyway....
Injector reaction time has more to do with trying to idle at really low pulse widths, not making power. Of course, this isn't an issue with even a 1000cc injector on a seqential system...
Last edited by boost junkie : 01-06-2006 at 06:32 PM.
AutoForums.com is the premier network of enthusiast-owned
enthusiast-operated automotive communities.
We operate more than 100 automotive forums where our users consult peers for shopping information and advice, and share
experiences and opinions as a community.
Injector impedance (resistance)
Pyrox, you're not too bad of a noob if you've already got a handle on Ohm's Law (kudos to you). I taught a lot of electrical one and two classes for Chrysler back when I was an instructor and there were always a few people in every class who had been doing it for years and didn't have a handle on it.
Linear Mode
