Voltage and Amperage requirements
Hello everyone. I was hoping to get some information from the collective brains trust about the power requirements of the FiTech system.
I've been having issues with voltage drop when cranking and it is playing havoc with my starting. Once fired up the car runs ok however I'm seeing the voltage drop to 9.5V on the white wire whilst cranking and the system is not liking it.
I've been reading up on the wiring requirements for the system and the issues with EM noise and I will be going into my car in-depth in the near future to make some modifications to the way the system is wired up. However I have a couple of questions first.
1. What is the peak amperage draw of the fitech when running, and under what circumstances would it reach peak amp draw. eg. whilst cranking? Under load? etc. or does the amp draw remain relatively stable whilst operating.
2. What is an acceptable operating voltage range for both the red main power wire and the white wire before the system starts to have "brown out" issues and generally becomes unhappy?
3. Has anyone tried using a 'Buck Boost 12v DC/DC converter' (see attached link) to stabilise the power to their Fitech unit?
https://s.click.aliexpress.com/e/bI9luOLQ
I appreciate any info you can provide.
Have you tried hooking the white wire directly to the battery. It does not need much amperage, but must stay above 11v. Wonder if you have a drop in your switch or fuse panel.
G'day Austin.
Do you mean run a wire directly between the battery and white wire. Or do you mean run a wire directly from the battery via switched relay?
What I noticed when testing the voltages on the weekend was that I'm loosing 1.2v between my battery (which is in the boot, (that's trunk for you Americans)) and the starter when cranking. So i'm already down to 11.5 ish volts before the power goes to any of the other systems in the car.
All power for everyting in the car (except the fuel pump which runs directly off the battery) is taken off after the starter motor. That means that the power for the white wire goes through the ignition and fuse box before it gets to the unit.
I changed this on the weekend to a direct wire from the battery that runs through a switched relay. However, no change. So I'm wondering about the main power supply to the fitech which is also taken off after the stater motor.
My charging system works the same way but in reverse. It puts power back into the main engine bay power wire which first goes to through the Voltage guage and the ignition and fuse box then back to the battery via the stater motor. I'm considering running a 10 guage wire directly to the battery but I'm not sure if this will cause issues with the fitech system.
Part of my problem could be EM noise and I will be going through it and shielding some of the wires in the near future.
Cheers
Rear batteries can be tricky. I have a 10awg that runs from my rear battery to the Fitech. Then 0awg for my starter.
I was running my battery cable to my starter, and the same post to the fitech red wire, and switched relay. The other side of the relay I connected to the fitech white wire. I noticed that while cranking, the fitech handheld lost power, so I had to connect a wire physically from my battery to the fitech red wire and also to the switched relay hot side for switching power on key on to the fitech white wire. That solved that problem; however, during cranking I am drawing about 400 amps to the starter which has to give you a voltage drop at the battery. With the battery fully charged, the most voltage I get at the battery while cranking is 10.5 volts. One time I let my battery get pretty low from not starting it for a few weeks, and it got down to 9 volts while cranking, but started. This low voltage while cranking at the fitech caused it to malfunction and foul out my plugs while idling. Moral of the story: Don't let your battery voltage while cranking get below 10 volts, or if you do get it started, it will foul your plugs. So now I disconnect the battery with cutoff switch if not starting for a few days.
https://tontio.com/car-battery/car-battery-voltage/
Pay particular attention to "Voltage when the car is starting"
Thank Bdhulderman.
I recently changed my set up so that my white wire draws power directly from the battery through a switched relay and I'm now having the same issue with my handheld controller. It goes to a white screen when I crank the engine and the only way to get it to come back is to unplug it and plug it back in again.
Not sure why this is happening given that the voltage should now be more stable than it was before. I'm going to do some re-wiring over the next week or so and try and see if I can alleviate some of the voltage drop issues I'm having when cranking. The more I think about it the more I like the idea of fitting a buck boost voltage regulator to ensure that the system is getting a steady 12v all the time.
They are cheap and pretty easy to install.
However I still haven't been able to find any details about the Amp draw and voltage requirements for the system so that I can get the correct one.
Although I think it's safe to assume that the system could draw as much as 20 amps (maybe even 25) under certain circumstances. Fuel pumps can draw as much as 15 amps at peak and the fitech can run a fuel pump in PWM mode straight off the ECU. Add to that the power it needs to run the ECU, read the various sensors (minimal) and power the injectors and I recon you'd be talking about another 5 - 10 amps on top of that.
So you also have your fitech red wire directly to your + battery terminal? That's what I had to do. I also put in a volt meter gauge under the dash that comes right off my battery terminal to see what the voltage is while cranking. That sounds like a good idea for these EFI systems to have that "buck boost voltage regulator" to prevent issues when trying to start your car with less than fully charged battery.
I just ordered this I'll try:
https://www.amazon.com/gp/product/B018WYNN22/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Anyone know the amperage draw of the fitech controller without driving the fuel pump? This may not be enough, depending on the impedance of the fuel injectors, which I can't find anywhere.
HAZAAR !!
I've had a massive win today..
Over the last week or so I've been re-wiring part of my car. This came about after I was having Huge (and annoying ) issues with both my tuning and my engine starting, both hot and cold.
I spent (wasted) months trying to tune the system to run correctly and not bog down under acceleration and to start easily and was getting absolutely nowhere. So with the assistance of an Auto Electrician mate of mine we finally did some testing and discovered that the system was not getting adequate or stable voltage whilst the motor was cranking. (9.2v on the white wire and 10.6v on the main power wire)
Exacerbating this was the fact that my blue ignition trigger wire was running very close to my plug leads and my HEI ignition system.
So I bit the bullet and rewired part of the cars harness to effectively give the Fitech its own dedicated 12v power source that is completely independent of the rest of the cars harness. I then re-routed the blue wire so that it passes around the back of the engine and comes up to the distributor from underneath, well away from the plug leads.
And wadyaknow when I hit the key for the first time it started instantly and settled into a nice idle. So I took it for a drive and I simply can not over state the difference. It is running soooo much better. It still has a couple of things that need adjusting but these are issues that I've created by trying to tune out problems that were actually being created by the poor voltage and therefor should now be pretty easy to sort out. (now that its running properly)
Much happier 🙂