2Lucky2tha7

iTrader: (3)

Is anyone running low impedance injectors on a daily/ consistent basis? I'm asking because last year I spent alot of time trying to make my low imp. injectors run off of my megasquirt by adjusting the PW % variables and opening times, etc., but all I ever got were blown fuses (the 2 amp fuse). I went at it for weeks, but I could never get it right. So, now I just run high imp. primaries and low imp. secondaries w/ resistors. I used this method on 2 other MS applications as well that I installed because the setups were all the same.
After that being said, this brings me to my next question:
Will I be able to definitely run 4 low impedance injectors using an MS-II processor, or should I just go with using an FJO low impedance injector driver?
I'm building my brother's widebody '79, so I'm trying to get everything together and bought as soon as possible so that it will be running in 3 - 5 weeks from now. I tried posting up again and asking about how to modify the 3.57 smd board, but I never got a response, so I guess I'll have to keep on using the 3.0 board, but with an MS-II processor for his car.

muythaibxr

You can run low impedance using the MS directly, but 2A is probably not a large enough fuse to do that without a resistor pack.

You will probably need a 5A or higher fuse on each injector channel.

Ken

2Lucky2tha7

iTrader: (3)

I meant the 2 amp fuse for the ECU power source. I always ran 10 amp fuses for the injectors.

gross polluter

I have been daily driving on low impedence injectors since October on the FC. 1.0ms open, 40% limit, 66us pwm, 1.1 pwm threshold. No issues except electrical noise which will be taken care of once I receive my driver board from Jean.

My rustang is running 8 low imp injectors, 4 per channel in parallel. I had the same issue of blowing 3 amp ECU fuses. Did not make much sense as the ecu grounds the injector, so it should not be drawing from the ecu power directly. After a minute of troubleshooting, I found that I had only one of the 5 ground wires hooked up at the engine. Trying to drive a .25 ohm load through a single 20ga wire did not work so well. For whatever reason, the ecu fuse kept blowing so the power was somehow being diverted. Connected the other 4 ground wires and have not had an issue since.

My only suggestion is make sure the ecu grounds are sufficient and well connected since running low impedence injectors is going to draw more current from those grounds.

2Lucky2tha7

iTrader: (3)

Thanks for the #'s
I remember that I tried 1.0 ms open up to about 5 ms and everywhere in between and I couldn't ever get it right. Although, my current limit was set to 80%instead of your 40%, my voltage correction was 0.1 and my time threshold was (I don't remember.....it was a number that was recommended and I still use it now). As for my grounds, I know they are definitely good because I have them meeting at my "ground chain" that I made in the engine bay and firewall. I am using all of the grounds. I will check them again though, but it's been fine for the last year and a half though.......

I'm just trying to find out where I went wrong..........
Thanks for the reply

peejay

I was running 1.0ms opening time, 75% PWM, and 1.0ms with 1.01 hardware, no problems. At least no problems on long drives, never took it to road course where duty cycle would be high for extended periods. .15 voltage correction.

2Lucky2tha7

iTrader: (3)

Wow, then I'm baffled as to why I couldn't get mine to work without popping the 2amp ECU fuse.......here is my thread from when it was happening, if anyone remembers it:
https://www.rx7club.com/megasquirt-forum-153/ridiculous-stumble-during-injector-staging-625072/
Thanks for your patience guys.

peejay

I have my ECU on a 5 amp fuse and my injectors on a 15 amp fuse.

The injectors really shouldn't be able to pop the ECU fuse since the ECU merely gives the injectors a ground.

Your injectors DO have their own source of power, meaning separate fused source, right?

2Lucky2tha7

iTrader: (3)

This is my thought process: although the ECU is only providing the ground, it is still (how do I say this in a comprehensible way....) a "mediator" in the whole 12V "circuit" for all 4 injectors, and not just a ground (if that makes any sense).
Also, when I kept popping 2amp fuses, I was far from home about 2 years back I believe, and when I went WOT up to about 7k rpms, the fuse popped. Well, all I had left was a 3amp fuse, and after I put that in and tried starting it, the ECU smoked a little bit and a few things got fried inside (I can't remember what though because it was soo long ago). To make a long story short, I sent it out to get it repaired, and I've been using a high impedance setup ever since.
And yes, all 4 injectors have their own direct power source with 15amp fuses (used to be 10amp).

I'm not as worried about it with my car as I am with another MS install I will be doing in the next few weeks on my brother's turbo'd 1st gen. It's just that the 3 installs that I have done so far have all been set up for high impedance (low imp. inj's w/ resistors), and I want to use all low imp. injectors for his setup.