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ECU pins left, FAN control, flyback redundancy

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hi! My 1JZ Ecumaster Classic equipped drift car is finally at the stage where all that's missing is some wires and a map.

I had a go at documenting the ECU pinout first. Attached to the thread.

I have pins left over and I honestly don't know what else is missing. It was always clear I won't run potentiometers or individual EGT probes, but to have this many pins left over is still surprising to me, especially on a Classis.

Did I miss something?

Whenever I asked for schematic help in groups people were suggesting two things. Both make sense to me. One side was telling me to dumb it down, simplify, some would even forego relays. The others were giving me advice on good practices, which in turn complicate things a bit.

Having both in mind, I can't decide which way to go with Fan control. ECU can easily control the relays and I imagine it's not difficult to set a water temperature trigger in the software. Then again, automatic switching during a run could bog down the car a bit and since it's a JZ, it's expected it will always need cooling, so at least for the radiator fans I could just turn then on manually before each run.

Thoughts and experiences?

Fuel pump relays, main relay and possibly fan relays will be controlled by the ECU. From what I understand, stepper motor pins on Ecumaster Classic have built in flyback protection. AUX pins do not. I bought Bosch relays with integrated Flyback Diodes because I didn't know which pins will eventually get used specifically.

Do you trust flyback protection from relays themselves? Do you normally use diodes despite for example in built pin protection?

I won't turn the car on until you good people have a good look at all of my documentation and confirm there are no major errors. This being my first wiring attempt, mistakes could still happen.

How bad is for example a coil discharge without flyback protection or blowing a diode and not noticing?

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Couple things I think we need for context;

What kind of fans are you running?

Single relay or a relay for each fan? the pinout sheet looks very much like a toyota fan relay arrangement...

What coil packs are you using? guessing not the factory 1J VVTi wastespark

The documentation on the ECUmaster ECU's is pretty hit and miss, but you are fine to any of the aux relay outputs to control relays. A relay coil is a small amount of current and does not cause a crazy voltage when switched off.

Flybacks are for PWM controlled devices.

I would strongly recommend using the H bridge for the factory IACV and the aux for fans.

You also dont have anything assigned for the tachometer, which you should use Aux 4 to do.

I personally would allow the ECU to have fan control. The software can allow some pretty complex control strategies if the fans kicking on mid run were ever to be an issue. Though if you do have a bog mid run from the fan kicking on there is probably something else going on.

Side note: the Classic has a particularly poor internal power supply circuit and needs all the help it can get. Use a relay, use an 18 or 16 gauge wire to feed that relay from somewhere close to the battery.

You can use VSS or a timer or rpm to prevent or force the fans turning on, and most importantly, you cant forget to turn the fans on which is what everyone with fans on a switch does at least once.

Should also be noted that MREL which is a Toyota term for the main relay, usually means a 12V high side controlled relay. Ecumaster only has low side outputs, you'll need to use the ignition key signal or the feed of the relay to turn that one on. If its still the Nissan S13 setup, this is part of the engine harness and I don't know what you have done wiring wise there, if anything yet.

Hi! Thanks for your reply!

Fans are 2 cheaper 80W fans (until they prove to be insufficient, then I am looking at SPAL or other brand names). I made sure the cowling is good to help them.

The car has no wiring, fuses or relays. Ground up build. I attached an older version of the schematic, I am fixing some of the issues others pointed out.

At the moment I have two relays dedicated to two fans to have more control over them and maybe bring them in staggered to have less of a spike. I would rather simplify and have one relay, less wiring, less weight, less failure points. Would one 30A relay be sufficient and not cause any issues?

Coilpacks are Yaris smart coils. They are getting their own relay that they share with other engine functions. ECU and Injectors have their own relay. The schematic does not show that yet.

There is no IACV. Tacho is an android tablet.

You mentioned Ecumaster AUX is fine for controlling relays without additional flyback protection. Are you sure that goes for Classic? I think that's only true for Black (which looking back would be the right choice for this car, but there's a whole story there).

Attached Files

80 watts / 12V = 6.66 amps each fan, or 13.3 amps for the pair. One 30 amp relay would be fine, but as discussed 2 for the sake of control would be better.

I have built many harnesses now for Blacks and Classics and yes any of the Aux's can control relays just fine.

From the ECUmaster Classic manual

"In the case of controlling solenoids with PWM signal (like VVTi or Idle solenoid) it is required to use a flyback diode"

If its not too late, sell or return the classic and buy a Black and a DBW throttle body. The price difference is small for the amount of improvements between the two. I wont even sell Classics anymore.

Attached Files

Had a whole message written, then lost it.

In short, can't return Classic for different reasons. Do want Black, DBW being one of the main reasons.

Thank you for your help so far. Is there anything else you'd want me to know before finishing my pinout/wiring? Something Classic specific if there is?

BTW how much do you know about stepper motor pins on classic? What does it mean they are ground and 12V switched? Do i have to change anything in the Client? I would like all 4 pins to control relays on the ground side.

There is no issue having a flyback diode (or resistor) at or in the relay, even with one inside the ECU. I disagree with the above comment that flyback protection is "only" for PWM controlled devices, it can be for either or both. While I've never had an issue on any ECU with not having flyback protection on a relay coil, it is good practice to do so.

Ground versus 12V switched, sometimes referred to as "low side" and "high side" switching is referring to which polarity is actually controlling the relay or device.

In the case of ground, or low side switching/control, this means that the one side of the device will have positive connected to it, typically 12V in a car, and the ground side is connected to the ECU and the ECU switched that device on and off using the ground (low side) the signal.

12V or high side swtched/controlled will have the ground pin connected directly to ground and the 12V side is what is turned on and off.

MOST ECUs use ground/low side switched for most of all of their outputs. Some exceptions will IAC or DBW throttle bodies that both use H-Bridges to be controlled, which is a whole 'nother discussion in that the ECU is switching both high and low side at the same time, however, I'm pointing out these outputs, to show that ECUs will have the ability sometimes to switch positive currents as well, depending on the specific application.

So, from the description above it sounds like the OEM ECU switches the main power relay for the ECU via a positive or high side signal, and would need to be modified in some way (additional relay or change the way the OE relay is wired), if you were to use the OE harness. It sounds like you're installing a whole new harness, including the engine side so you will just follow the ECUMaster instructions for this.

The left over pins are just for additional IO, if you chose to use them. If you're not using them for anything, don't sweat it, this just means you can add more sensor or devices later, if you ever feel the need to. You should see how many pins I have left over on some installs with certain ECUS, it sometimes feels like I am wasting the ECU due to having so many IO pins open, because they were basic or somewhat basic installs. lol

Also, the Classic is a great ECU, and will work well.

Hey! Thank you for taking the time to write this up.

I would like to ask one last bit about stepper pins or 2 state outputs in general. They are able to switch both low and high side as you explained. I kind of had that down myself too.

In my practical example, they will be used to control relays on the ground side, terminal 85. Do I need to select a checkbox in the Client to "tell" the ECU I want to use Gnd? How does the pin "know" what polarity to send through?

It's worded clumsy, but I am sure you get what I am asking.

SOME ECUs have the ability to select the polarity to control, and usually only for some pins.

MOST ECUs are setup to use one polarity only, like your Classic, are all low side control IIRC. This is where reading the instructions will help you to know how to setup the circuits for the devices controlled.

As you have spare AUX outputs free, use them instead of the steppers. As you said, steppers have 2 states, +12v and ground. I can't recall exactly, but I'm pretty sure when the ECU is powered ON, those pins are connected to +12V, unless they are triggered when controlling an output. When the ECU is OFF, they are directly connected to ground, which means your fans could be running continuously if the pin 86 is from a constant +12v.

As stated in the manual in regard of the stepper outputs, if you use a "Hot at all time" source to feed pin 86 of a relay (or whatever component you are controlling), when you want to turn off ignition, it will keep the ECU powered via the internal flyback diode. Basically, the ignition won't turn off.

And yes, as Chris said, all AUX outputs are lowside (they can only provide ground)

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