Will higher impedance injectors work in the V12…or not… esp in race type conditions,…
Dear Anon,
The last of the v12s with the Denso ECUs ran high impedance injectors, so the answer is yes.
The question you are asking is not very well defined in its scope:- the desired injection time for a different specification injector will alter unless the ECU is remapped, so you can’t simply throw anything in as a substitute and expect it to work. The driver circuitry used for low impedance injectors canbe used to run with high impedance injectors but won’t likely give the desired result by simply swapping components around.
kind regards
Marek
Hi Jerry… well I installed them anyways… the engine runs, how well I do not know until I am able to try some rubber to the road I guess… the injectors are the same pound rating, so I am hoping it will be good…! ?..Art.
The low impedance injector are driven with a full 12V by the ECU for an initial fraction of their opening time.
I guess that gets them open quickly with high current. The remaining fraction they have series resistance switched into circuit which limits the current they receive. A high impedance type will probably work but may not give correct opening time right across the engine operating range. In closed loop cruise maybe no problem at all, but WOT is a risk.
The modern aftermarket fuel injection system on my coupe allows a menu selection of high or low impedance injectors, so it presumably drives them differently and does not need external resistor packs.
A high impedance type will probably work but may not give
correct opening time right across the engine operating range. In
closed loop cruise maybe no problem at all, but WOT is a risk.
See, I would consider idle a bigger risk. If the flow rates are the same, WOT
is going to have the injectors open a long time, and any differences in
pop-open and slam-shut rates will be relatively minor. At idle, though, the
injectors barely pop before they shut again, so differences in pop-open and
slam-shut rates could make a huge difference in fuelling.
Of course, there’s less chance of engine damage at idle, so as long as you’re
not trying to pass EPA tests, maybe it’d be OK.
– Kirbert
I agree with the others. The engine may run but not ideally. Over the years, I have seen a handful…maybe 3-5 situations…where the wrong impedence injectors were fitted…that’s for the 5.3 liter pre-HE and HEV12 and several of the later six cylinder engines with the AJ16 setup. In all of those cases, the engine ran rather poor, but once the proper impedence injectors were fitted, the engine ran properly. So, unless you intend to change the driver out, you should fit the correct impedence and flow rate injectors. SD
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Driving a high impedance injector is a slightly different task to driving a low impedance injector.
The low impedance injector typically needs to see a high current to open it and opens very quickly. Maintaining a high current in the injector will overheat it and will make it take a longer time to turn off. Once opened, the current is ramped down because the current needed to keep it open is only a fraction of that needed to get it to open. By contrast, the high impedance injector has its solenoid coil engineered differently, in that it expects to see a constant average current. As a consequence, it’ll probably take longer to open and longer to close. The high impedance injector may not like having an initial high current pulse put into it.
Even if the opening minus closing time of the two injectors in question is the same (i.e. the “dead time”, when the mechanical action has yet to catch up with the electrical instruction), then it will likely have very different characteristics whenever low pulsewidths are commanded by the ECU:- imagine the loZ injector takes 0.5mSec to open and 1mSec to close whilst the hiZ injector takes 1.5mSec to open and 2mSec to close. When the ECU commands a pulsewidth of 1.4mSec, the loZ injector delivers 1.9mSec of fuel and the highZ injector delivers zero fuel. At 1.5mSec, the loZ injector delivers 2mSec of fuel and the hiZ delivers 2.5mSec of fuel, probably erratically as it it is told to shut as soon as it has opened. At 3mSec, the loz injector delivers 3.5mSec of fuel and the hiZ injector delivers 4mSec of fuel. The low pulsewidth behaviour is probably separately programmed in in the ECU as anything below ~3mSec is sure to be very injector specific and related to fast it opens and closes. Injectors are often non-linear at low pulsewidths.
The typical way people try to compensate for fitting the wrong component is to alter the fuel pressure or fiddle the temperature sensor reading, but this adds or removes a fixed percentage of fuel, rather than a fixed amount of time’s worth.
In addition the fluctuation and compensation built in for voltage may be different for the new injector - your car may be hard to start as the starter motor drains the battery or the winter temperature alters the injector voltage compensation, or as the alternator voltage alters, let alone the mis-fuelling caused by the old fuelling algorithm.
In short, it is unlikely to work as well as the component that was originally chosen.
Take a look at the Megasquirt website msextra.com for more information about how all of these factors interract, how they are measured and how they need to be set up.
kind regards
Marek
Many thx for your continuing info…beinjg a mere cabinetmaker , most
of this is a higher language… I am just wondering if perhaps I could
remove the old injectors pintle and swap in the newer 4 hole
sprayers…?..Best Wishes…Art…
Terrible idea to attempt to “rebuild” any injector. And by rebuild, I mean pull the innards out and replace with some substitute parts. You are much better advised to find a disc style injector with 4 or more holes that has the same ohm rating and flow rate as the proper ones for your engine. I never found an injector that would meet those criteria for the HE V12 engine. The other poster MarekH may have done that with the extensive work he has done with I believe the Megasquirt adaptation. It would most likely have to be an injector using an o-ring fitment to a custom made fuel rail. SD
Dear Art,
Your best bet is to remove the old injectors, clean them and refit them. The performance and spray pattern will likely then be perfectly adequate.
kind regards
Marek
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