[PSIG]

I am wondering if I can at least test - start my car without any resistors?

If these are the 6-ohm injectors - yes. Paired on a single channel, the current is under 5A at over 14V. You're good to run no resistors at all. Do not use cheap imported connectors, pins or terminals. Use both IDC pins for each channel.

Most board circuits (official designs anyway) have traces to handle up to 8A, and of course the MOSFET is rated much higher, but the IDC connectors are often cheap 1A rated. However, they are available up to 3A, and it uses two per-channel, so no problem. All that said, Josh did some high-amp testing of the IDC connectors and light wiring, and they handle far more than I ever expected. There's a video somewhere.

[EDIT] If you're concerned, remember the duty cycle is 85% max (if you ever use that much), which would be under 4A at 14+V. Less for lower rpm and pulsewidth, so at 700 rpm idle, the average current is ±56 milliamps per-channel, at 4-squirts per cycle. Check my math on that.

[JHolland]

It should start and run if the battery is OK and its not -40C. Automotive standards call for operation down to 6V during cranking, that would give you 1A though the injector, if you assume that that is the minimum current required then running 6 Ohms + 2 Ohms resistor would still allow starting down to 8V.

[crackedheadtv]

The speeduino of mine looks like this:

448777417_529074436110866_3255481604603116766_n.jpg (191.53 KiB) Viewed 2040 times

But I ordered 2ohm 50w resistors as I had conversation with myself and I'd rather be safe than sorry. I put a lot of work and money in my project and honestly I don't want to fix speeduino later if sh*t happens. I am assuming adding 2ohms is not very critical and shouldn't mess my injectors dead times to the situation where I won't be able to tune it properly?

And like I mentioned before ( I think ) if everything's alright there won't be a problem to sell these and buy set of proper high-z injectors.

And with resistors in place, what should be my duty cycle and dead time for first time starting the car?

[PSIG]

You do you. You have guesses and hunches, and you have math and values. Take your pick and move-on. Adding 2-ohm resistors may not prevent running, but at low voltages such as cranking the injectors may not open. Or they might, slowly. Or be fine. You can't know latency without testing what the effects might be. I would keep an eye on cranking fueling to be sure they are working, and reasonably quick to get enough fuel to start. It's no big deal if they work slowly or not at all, and good that you know to expect they may have issues to watch for. You can test for dead time with O2 once it's running.

Ah, stories: Long-time members here remember my mistake when testing a TBI between ECMs, with 1.2-ohm injectors. I used 5-ohm resistors (total 6.2 ohms), and a plug to swap between the factory and my ECM for test comparison. In swapping the last time, I forgot the connection to the resistors, and drove on the 1.2-ohm injectors. I was wondering why idle was extra rich, but OK with O2 correction. I was shocked when I found the 1.2 ohm injectors running happily with no resistors. Of course I reconnected them! And the tune returned to normal, but the stupid mistake gave me a lot of confidence for what the injectors and circuits would handle. Do your thing.

[crackedheadtv]

You do you. You have guesses and hunches, and you have math and values. Take your pick and move-on. Adding 2-ohm resistors may not prevent running, but at low voltages such as cranking the injectors may not open. Or they might, slowly. Or be fine. You can't know latency without testing what the effects might be. I would keep an eye on cranking fueling to be sure they are working, and reasonably quick to get enough fuel to start. It's no big deal if they work slowly or not at all, and good that you know to expect they may have issues to watch for. You can test for dead time with O2 once it's running.

Ah, stories: Long-time members here remember my mistake when testing a TBI between ECMs, with 1.2-ohm injectors. I used 5-ohm resistors (total 6.2 ohms), and a plug to swap between the factory and my ECM for test comparison. In swapping the last time, I forgot the connection to the resistors, and drove on the 1.2-ohm injectors. I was wondering why idle was extra rich, but OK with O2 correction. I was shocked when I found the 1.2 ohm injectors running happily with no resistors. Of course I reconnected them! And the tune returned to normal, but the stupid mistake gave me a lot of confidence for what the injectors and circuits would handle. Do your thing.

The dude ran these injectors on LINK ECU with peek n hold disabled, he offered me not to put any resistors for the injectors and said that everything's should be fine, but like I mentioned previously - I'd rather be safe than sorry as I am not very good at electrics so fixing burnt speeduino is not exactly what I want. Let's hope those 2ohm resistors won't mess up everything too much and I'll be able to use injectors I have safely.

Actually I was thinking of not using any resistors, but read here and there and there's no accurate answer, so... Soon I should receive my resistors and be good to go!

Thanks for your reply!

[crackedheadtv]

Ok, so I installed resistors for injectors and now I am facing other issues lol. Here’s topic: viewtopic.php?p=69082#p69082

So…

My question now, what should be my starting point for these injectors with 2ohm resistors - somewhat 1.5?

After switching JP2 jumper to VR ( sensor is hall, but “SS10893 is a hall sensor, power is 12v and signal range goes from 4.5v to 18v.” ) when crancking tuner studio sees rpm. It sees other sensors as well, reacts to throttle ( calibrated ) and after crancking few times it tried to start, but didn’t, then with maybe half throttle pressed ( maybe less ) I got a loud bang in exhaust ( backfire ?? ) which indicates that fuel is being delivered and spark present.

This is first time me doing this so I am trying to be really careful of what I am doing.

Can this be caused by injector dead time?