[JHolland]

It is probably a combination of the higher resistance and a lower energy requirement, at what current do they open?
The inductance is fairly constant across temperature and hence so is the current required to open the injector. Once you have measured the required current is fairly simple to run a Spice simulation to determine how long it takes to reach that current with different resistor values.
I didn't mention temperature above but the injector resistance will vary across temperature due to the temperature coefficient of the copper windings, if you measure the resistance at 20C then you will need to allow for a higher resistance at higher temperatures.
You also need to calculate the inductance from the rise time of the current, inductance meters and bridges rarely have enough drive strength for a low impedance inductor, adding a series resistor helps but there won't be enough current to generate any magnetic flux in the core.

[PSIG]

I did not measure current as they performed well (expected or under 1ms latency) throughout extensive tuning in each case, so I had no cause to measure it. Each was by the site calculator, which was ±5-ohms for these and other "low-z" I've tried so far, though never as small as this one. You have found an exception to my findings, and my concern is to find a limit to proper function at some identifiable point that users can plan to take different action. A rule-of-thumb if you will.

At this point, my only rough-guess would be under 2-ohm or 1.6mH, but I can't be sure that's the correct level or cause. As the number of instances would likely be low, perhaps only a note in the Wiki injector hardware section to test latency on the engine (always anyway), and use alternative methods if found to be abnormally high.

[JHolland]

I don't think it will be simple to specify a rule, its almost certainly down to the energy required. If you have a 2.1 Ohm injector and a 5 Ohm resistor then you will be opening at less than 2A at 14V, if you're getting reliable starting then you are probably opening at under 1.5A, at low currents like those there will be considerably less divergence.

[nuno_leonor]

Thank you all for your comments and I’m sorry to take so long to reply, but I’ve been a little bit overwhelmed with this project.

Special thanks to @JHolland for providing the injector characteristics, it was valuable information.

Here’s some additional details and what I have found so far.

• Despite the online calculator compute that a 6 Ohm resistor should be used in series with the injector, I’m using a 9 ohm resistor, so perhaps I’m limiting the current too much, which may prevent the injector to work properly under low voltage (while cranking)

• My starter motor and my battery are far from new, and I noticed that while cranking the voltage can drop up to 8.5V, this also do not help

• If I inject some gas (in test mode) before cranking, I am able to start the engine. However a few strange things happens (at least for me due to reduced knowledge):

• If I set the injector characteristics to 468 cc/min, the engine won’t start;

• If I set the injector characteristics to 200 cc/min, the engine starts, however it only runs extremely rich <10:1. If I start to tune the tables so I can approach the 14.7 value, the engine stalls. I was only able to run it extremely rich.

• Additionally, using a scope to the signal generated by the AFR sensor, I noticed that the readings are affected by small pulses synchronized with the coil ignitions. I don’t know if this is normal and if affects the readings.

• Finally, sometimes while cranking, there was preignition and fire was coming out of the throttle body, despite the fact that while idling the ignition is occurring at 8º as referenced in the car manual. I used a stroboscopic light to check this.

I included a logfile when I first crank it and stop, then crank it again and the engine starts and give it a few revs.

For all these reasons, at this point I decided to revert all the modifications to stock carburetor, study the sensors signal outputs in detail, study the stock timing while cranking, idling and accelerating, and then modify to injection in a step by step basis, that is, first I replace the ignition system, and then the injection. I’m also considering replacing the injector by a high-impedance injector so the resistor in series is no longer required.

Any thoughts about this?

Thanks again

[PSIG]

Responses in pink to avoid lots of quotes.

• Despite the online calculator compute that a 6 Ohm resistor should be used in series with the injector, I’m using a 9 ohm resistor, so perhaps I’m limiting the current too much, which may prevent the injector to work properly under low voltage (while cranking)

Far too much resistance, even for a "normally responding" injector. Follow the calculated resistance normally, or I would drop-in a 5-ohm as that's what I mostly use, just for testing operation and response. This should also verify the expected operation by @JHolland.

• My starter motor and my battery are far from new, and I noticed that while cranking the voltage can drop up to 8.5V, this also do not help

An issue. Standard automotive guidelines are around 10.5V cranking minimum in a healthy system. Lower voltage can bring many of issues, from no injection, no or weak spark, ECM brown-out, poor sensor operation, low fuel pressure, etc.

• If I set the injector characteristics to 468 cc/min, the engine won’t start;

• If I set the injector characteristics to 200 cc/min, the engine starts, however it only runs extremely rich <10:1. If I start to tune the tables so I can approach the 14.7 value, the engine stalls. I was only able to run it extremely rich.

Expected response from excessive resistance and slow injector operation.

• Additionally, using a scope to the signal generated by the AFR sensor, I noticed that the readings are affected by small pulses synchronized with the coil ignitions. I don’t know if this is normal and if affects the readings.

All installations are assumed to use resistor spark plugs and suppression spark plug wires. If you don't have those, get them.

• Finally, sometimes while cranking, there was preignition and fire was coming out of the throttle body, despite the fact that while idling the ignition is occurring at 8º as referenced in the car manual. I used a stroboscopic light to check this.

That symptom will likely solve itself with lower resistance and higher voltage.

[PervertAngelMarc]

Do these zeros need changed to 100+