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RB25 ECU master loom help needed..

EFI Wiring Fundamentals

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hey everyone, first time posting on here, I'm in the upgrade stages of my s14 RB with engine management and requires wiring modifications and I want the best / easiest / most cost efficient way out of this.. I currently have a fully forged RB with an MMP x7362R turbo making 480bhp at 1.2 bar boost on my power FC, it still has AFM and I think now the apexi are out dated for certain closed loop control and many pressure monitoring safety systems, the guys at stone motorsport here are amazing and do all my tuning and highly recommend the new ECU MASTER classic black edition, features I like are the data logging, wideband system, built in MAP sensor and use the Bluetooth set up and use a tablet dash set up.. HERES THE ISSUE, the ECU master dealer can supply an adapter plug to use my existing loom plug but I'm not a fan as I want to upgrade coil set up, wont need AFM wiring and ill want to use the additional fuel and oil pressure sesnors so I think adding to the OEM loom is just mad, id like a new loom, I'm a capable wiring man but if I was to wire from scratch id be lost, I'm confident that if I had a diagram to work off that id make a tidy loom, has anyone on here done a loom for an RB for ecu master classic black and documented it??

looking forward to replies, thanks..

G'day Shane.

I haven't installed an ECUMaster ECU before, but I've worked on many Nissans of that generation. You've got two options really. Yank the original loom, steal all the connectors, source new pins and build from scratch, or modify the existing loom.

I'd give modifying the original one a go, as the nissan looms of that generation are pretty nice in that they only have one connection to the body wiring harness. Yank it, get it on the bench, and remove all the coverings. This will let you really check out its condition. Try to keep its shape (branch points) intact with cable ties as you remove the covering. You can then add and remove wiring as you need.

Thanks for the reply buddy ..

I can can get loom out and inspect no stress and inspect, where I'm afraid and will struggle is where to pin certain wires with the ECU master maybe it's the wording , for example I'll need to add oil pressure and fuel pressure sensors , on the ECU master pin out diagram it doesn't list those sensor wires so I wouldn't know where to put in .. Likewise with s1 rb25 I have the external igniter for coils so how to pin that to the new ecu and CAS signal wire where on the ECU master does that go .. And it can control cooling fans I hear which I have now on a relay and switch myself but where would I pin the relay signal wire to the new ecu ect ? I find the pin outs very confusing , if I knew what to put where I'd make it all no prob

G'day Shane. Well, you're in the right place, because we can absolutely help with that :-). Having no experience with ECU Master ecu's, I've just had a quick skim of the user manual and looked at the pinouts. It looks like they've got a mix of dedicated sensor inputs that have to be a specific channel, (Crank, Cam, IAT, EGT and Knock) and generic inputs that you could wire your pressure sensors to.

What was the RB originally out of? Just wondering how the RB loom is interfacing to the S14's body harness wiring?

I think you might be getting to the stage of building a loom pretty much from scratch for it, might get a bit messy using the original at this stage.

For the specific bits you've mentioned though:

Oil pressure signal to pin 20 on the black plug, analogue input #1

Fuel pressure signal to pin 3 on the black plug, analogue input #2

You'll need to give these sensors +5v sensor supply power from pin 23 on the black plug, and a sensor ground on pin 17 of the black plug.

You can do away with the external igniter, as the ECU Masters ECU can handle the primary coil currently directly, so each coil needs +12V power to its positive terminal, and its negative terminal gets wired to each of the ignition coil inputs of the ECU. Use 20AWG wire for this.

For your CAS sensor, have you still got the original trigger disc installed?

that's a lot of info even I wasn't expecting thank you..

ill just give you a little more info, the previous owner of my car had a full OEM loom but he took the car to mike deane at deane msport (james deans brother), where he modified the loom to use a custom relay / switch panel in the centre console with main fuses and ECCS relays in the glove box along with my power FC..

the engine is a series 1 rb25det out of an r33 gtst skyline.. and the dash cluster is just a home made assortment of gauges I put in myself, oil temp / pressure, boost , rpm and coolant temp..

is this the ECU master you were going off? http://www.ecumaster.com/wp/wp-content/uploads/2016/11/black_booklet.pdf

also yes the car still has OEM CAS with standard trigger wheel, do you recommend an upgrade?.

I should mention the max ill ever want to achieve is 500bhp, that's more than enough..

sorry for the many questions but here are a few as your being so helpful LOL .. if you cant get around to answering them all then that's fine :)

1) do the oil and fuel pressure sensors not just have 2 pins? id presume a supply and signal earth? not a live, earth and signal?

2) with certain aspects of the ECUs control im unsure of how it all works, with the fuel pump and cooling fan closed loop control is it a case of the ECU activates the low current control side of the relay? also if so how do I know if its negative / positive switching or does it even matter?!

3) the RB25 has 2 idle air control valves, well 1 IACV and 1 cold start valve, I think I previously read that within 7 minutes of being energised its either fully open / fully closed so if running the ECU master could I just manually fully open / close the cold start valve and let the ECU just control the IACV?

4) so you mentioned the coil primary circuit being controlled by the ECU (thank god as the ignitor pack on the plug cover is a pain), the coil will only need 12v supply and the signal earth just 2 wires operating the coil?.

5) ill want to use the tablet dash so I presume all sensor inputs will have to go to the ECU and then its transferred to the dash VIA Bluetooth or cable, so does the alternator charge light have to be wired back into the ECU or will the ECU automatically detect the voltage?

6) ill want to run the wideband 02 sensor set up and not sure how that'd be wired in also, im not 100% sure if its CAN signal to the ECU, if so is it just run the 2 CAN wires to the ECU?!

7) id want to run boost control so where would I wire the solonois?

8) if I wanted to run HI / LOW boost and antilag switches where would I wire into.

sorry for the many questions, im well able to fault find wiring and iv electricity fundementals off pretty good its just compiling the wiring diagram id struggle, iv no doubt id make a nice tidy loom if I had a diagram to go off of.. would it even be possible pay you to draw me up a detailed diagram to go off? as im very unsure of whats acceptable of common supplys / fuse sizes and wire thickness

any scrap of info at all is hugely apprieciated..

Hey dude. No worries answering questions, it's all part of having access to the forum! I'm busy writing sections of the update to the Wiring Fundamental course right at the minute, but I'll put something together for you after work this evening. I wont do a complete harness design for you, as there wouldn't be any learning in it for you, but I absolutely can get you started, and let you look at a couple of harness design documents I've got kicking about... Then we can work it out together, plus everyone else reading this can learn too! :-).

Thanks so much, I couldn't ask for better !!. No panic anyway it will be a summer upgrade .. Looking forward to it

The document I'd been getting the pin numbers out of was this one: http://www.ecumaster.com/wp/wp-content/uploads/2016/11/emu_manual.pdf

It might not actually be correct, as its for the classic, not the black. I can't see a manual available for download on their website for download, but they have it in the help section of the ecu configuration program, i've attached a screenshot of the pinout to this post.

1: Often the sensors used to power dashboard gauges only have two wires, and they're not really suitable for using as an input to the ECU. I suppose its possible, but you'd have to manually create all the calibration data. More commonly a three wire 150psig sensor is used that takes +5V, and Sensor Ground, and puts out a signal that varies from 0.5V = 0psig, and 4.5V = 150psig. These are my favorite ones:


I believe there are cheaper brass bodied versions around, available out of china, but I havent had any experience with them yet.

2: Yes, you're spot on there. Usually the ecu is used as a 'low side switch', as in, it gives a ground connection to the relay coil. So you power one side of the relay coil and connect the other to the ecu output channel. When the ECU wants to switch the relay on, it'll give the switching coil a ground. In most ECU's you can actually configure whether they switch on the high side or the low side, but low side it more common, so go with that :-).

3: Ahhh, yes, Nissan, I'm sure they had a reason for it, but the idle speed control on the RB really is a little... odd, in my experience anyway. This is all from memory, but I'm pretty sure this is how it goes. There is one of these:

Which simply gets supplied 12V when the car is running. It has a heater element and a bimetallic spring inside, and closes up more and more the longer is it powered, lett less and less air bypass the throttle. It's like an electric version of an old wax-stat valve, which did the same thing, but used the heat from the coolant to close up a passage, instead of an electric heater. Personally? I'd yank it and do without it. Racecar.

There is also one of these:

Which has two parts. The AAC (auxiliary air control) valve (brown plug) is the actual idle valve, you can drive it with a PWM signal to vary the amount of air it lets bypass the throttle. The other valve (purple plug) is the FICD (fast idle control device) valve, and is either on, or off, to allow extra air to bypass the throttle when the air conditioning compressor or power steering pump is placing extra load on the engine.

4: Oh, yes, I lead you slightly wrong in the last post, I forgot that the nissan coils of that generation have one side of the secondary winding broken out on the connector too, most conventional (not internally ignited) coils dont.

Pin out for those coils is:

Pin 1: Coil primary winding negative. These go to each of the ignition output channels of the ecu. Once again, the ECU acts as a low-side switch, allowing current to pass through the coils during the dwell period to charge them up, then cutting off the flow of current to cause a voltage spike and resulting spark when its needed.

Pin 2: Primary winding positive. These pins are all supplied 12V from the ignition coil relay.

Pin 3: Secondary winding positive (dont get confused by it being called the positive, we actually ground it, its to do with which way electricity actually flows, and where the heat builds up). These pins all get grounded to the cylinder head (very important). It allows the secondary winding current to flow in a complete circuit, only broken by the spark plug gap, which is where you want the big voltage drop to be, so you get your sparks there.

5: Yes, your ecu should be able to give you a warning if the alternator isnt charging by looking at the current system voltage, and the engine RPM. If the engine rpm isnt zero, i.e the engine is running, and the voltage is below a certain limit, then you've got a problem. You will have to supply the alternator field winding with 12V to get the alternator to charge, but I think this is in a sub-harness in the nissans, not the main EFI harness?

6: Your ECU has a built in wideband controller, and the documentation has info on how to wire up the sensor. The wideband sensors have 5 wires. Two of them are for the heater, one of which get 12V power from the ignition relay, the other of which goes to the ECU, which low side pwm switches it to get the sensor to maintain the sensor at the right temperature. The other three are for the reference cell voltage and the current pump. They will all be wired directly to the ECU, which will list them as something like Vs, Vs/Ip and Ip.

7: One side of your boost control solenoid gets power, the other side gets connected to a spare auxiliary output on the ECU, you then configure in the ecu software which pin you've connected the boost control solenoid to.

8: One side of the switch gets connected to ground, the other to a spare switch input on the ECU, you then configure in the software which switch input you've wired it to.

I've got a couple of things to take care of for the rest of the evening over here, but possibly later tonight, or tomorrow evening I'll post up a google sheets document which specs out a loom I built for a friends racecar recently. I'll also post up another slightly modified version with your ECU and the bits I know about your car and we can start filling in the connections :-). Its not a visual wiring diagram, as I dont have an easy way of drawing those, but all the same information is there :-).

Hope that helps!

Attached Files

Wow that's all great info thanks so much .. That's all great I didn't realise the inputs and outputs were up to yourself which one u choose to pin to and it's then configured , that's great I didn't realise it was that user friendly .. And it's new to me but your 100% correct about the pressure sensors being better 3 wire, only experience is bad with that stuff is fitting oil pressure guages..

Would I be right in saying for coils and injectors the ECU gives the power and ground to the components ?. But for the high current side of the fuel pump externally fuse and relay it and just pin the low current control side of the relay to the ECU?. Reason I ask is I'm wondering how many relays will be needed approx, so 1 relay for ecu power I presume and 1 for fuel pump and 1 for starter?. I'll post pics of my current switch panel at the weekend and it seems u could do away with a few of the switches (fan and fuel pump) after that all id have is wipers , ignition and Heaters ..

Sorry this took a while to get up Shane, I had to remove any identifying information from it. This is how I document my harness wiring, combined with a hand drawn diagram of the branch points, run lengths and connector locations, It's a grouped list of all the connectors in the harness, with a pin listing of each, and what connector/pin it goes to.


Let me know if that link doesn't work. I made it viewable to the public, but not editable. You should be able to copy and past bits and pieces of it though, to give you a start on your own design.

In response to your last post:

With the inputs and outputs, some of the IO pins on the ECU Master ECU's are fixed in their function, so just make sure there isn't a dedicated pin for something you're wiring into it before you connect it to a definable input pin.

You're 50% right about the coils and injectors. You supply them with 12V via a relay, and the ECU provides a ground connection when it dwells the coil, or fires the injector.

I find many modified street car / club level race car installs I do end up having four relays.

The first I call 'Main Power', which is like the accessory stage of the key barrel in a car. It provides 12V to the ECU, dash, any loggers and things you want to connect to while the engine is not running.

The second I call 'Enable Power', and provides +12V to the fuel injectors, ignition coils, o2 sensor heaters, etc... Things that are only powered when the engine is running, or 'enabled'.

These two relays are controlled by the driver. It means he can turn on the ECU's, and crank the starter motor without actually enabling the engine to start, to get oil pressure for example. He can then turn on the engine enable switch, and if he cranks the engine again, it will actually start.

The last two relays provide +12V to the fuel pump and cooling fan, and are controlled by the ECU. This means you can do away with the manual fuel and fan switches you have. That being said, I often install a cooling system override switch which connects to an ECU input, and is set to tell the ECU to turn any and all cooling fans on, and run the water pump as fast as possible (if the car has an electric pump). It's also really common to have an override switch on the fuel pump relay which turns the pump on, for pumping out excess fuel, or testing purposes, etc....

that's a huge leg up thanks, ill scribble down a hand drawn pic of what I think so far later and post it up, you might tell me how far off I am LOL thanks again, all a huge help..

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