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Chris Rummel's easy follow RB into Z wireing guide

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Andy I wish I could help you out there, but I don't recall seeing that on the RB25 harness, probably because the 25 uses high impedence injectors.

I think I would have remembered seeing that.

Maybe on of the guys that did the 26 would be more help with this question. try posting is as a seprate thread.



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Hay Andy,

How many wires does that dropping resistor have? Can't tell with the picture. If it only has two wires, then it is most likely not for the injectors but rather the fuel pump.

Look closer at the FSM diagram. Also, the dropping resistors do not lower the voltage to the injectors. The voltage is pulled low by the ECU and the dropping resistor limits the amount of current that goes through the injectors so as not to fry them. Voltage is not the enemy, current is.If you do have to have a dropping resistor then what I found out is that one wire, usually the white wire goes to the switched battery supply and the other 6 individual wires will go to one side of the injector. The other side of the injector goes to the ECU. When the key is turned on, the injectors will have 12v on both sides. When the engine turns over, the ECU will pull one side of the injector low with a ground pulse. This will pull the 12v low causing current to flow through the injector. The injector opens at this point. I have an RB20DET with high impedance injectors that do not use the dropping resistor pack. The picture that you have looks just like the dropping resistor used for the fuel pump on the RB20. It keeps the pump for getting to much current and burning up. Make sure you check very closely with the FSM. I thought my dropping resistors were missing from the swap until I took a second look at the RB20DET FSM and found that it did not have them. I kept confusing the fuel pump dropping resistor with the injector dropping resistor pack.I'm not saying that you don't need them. Just make sure they are the right ones.

Picture of dropping resistor pack for injectors


Picture of Dropping resistor for fuel pump


Hope this helps.



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Thanks Chris & Chrism for your replies. I think that I have got this sorted now so I will write it up below and contribute to your thread. The usual proviso that you should check and satisfy yourself that this is correct before copying me and powering anything up applies. There is no warranty with this info so please don't blame me if things go wrong!


IMPORTANT - this information on what I did is for those people doing the RB26DETT swap only.


With the RB26DETT conversion you must wire up the dropping resistor to power up the injectors otherwise you will damage your injectors. You can either buy an off the shelf dropping resistor and wire it in yourself or do it the easy way like me as set out below:


On the GTR the dropping resistor is located on a metal plate bolted to the injector side strut tower which also accommodates the PCM Valve (boost solenoid).




The dropping resistor is a shiny oblong aluminum covered box with a solid inside. There will be seven wires coming out of it - 6 black and one white all ending in a grey plug.




When you buy your motor make sure that you get the dropping resistor and to make life easier also make sure that you get the plug that connects to it with about 6 - 7 inches of wire to spare so that you can then easily connect onto it when your doing the install.


The car that my engine came out of was a JDM R33 GTR. If your engine came from a different model then the colours of wire in your setup may be different.


Essentially, power goes to the injectors via the dropping resistor as shown in the diagram in the post above provided by Chrism.


You need to find the wires leading to the injectors and then connect these to the dropping resistor. Then you need to provide power to the dropping resistor itself.


The injector power wires in my R33 loom were coloured:


1 - Red

2 - Red/Blue Stripe

3 - Red/Black Stripe

4 - Red/Green Stripe

5 - Red/White Stripe

6 - Red/Yellow Stripe


I traced them to a double plug connector leading from the eccs connection with the injector harness, past the turbos and towards the front of the car. I verified that they linked to the injectors using a test meter. The injector has two wires, a ground trigger linked to the eccs and a positive feed linked to the dropping resistor. For the avoidance of any doubt the wires we are talking about are NOT the injection trigger wires which link directly to the eccs and are predominantly white in clour.





The wires in this plug were the same colours as those leading to the dropping resistor. I cut them off the plug and directly connected them to the dropping resistor using solder connections covered with shrink wrap. Because I had got the dropping resistor connecting plug, I was able to simply connect each colour coded wire to its counterpart wire of the same colour. This has placed my dropping resistor on the same side of the car as the turbos but a little further forward. You could easily shorten or lengthen the wires to enable you to place the resistor anywhere you please.


Next I needed to get power through the GTR bulkhead plug. To do this I selected a redundant heavy gauge thick solid yellow wire and cut this both sides of the black bulkhead plug. This then gave me a clean route through the bulkhead without any cutting of the plug or any messy extra wires.


I gave the injectors power by connecting the yellow wire into the thick solid red wire AF04 that Chris uses to power up the injectors in the RB25. I then extended it and connected the other end to the white power wire for the dropping resistor.




Hey presto - you have just powred up your RB26DETT injectors via the dropping resistor.


Hope this helps.

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Andy, that is an excellent addition to this thread, and exactly what I wanted to have happen with this. I want it to continue to evolve with any new additions that make the swap wiring either easier or as in this case more diverse applying to the RB26 as well as the RB25.

These additions only make it easier and more clear for everybody.

Outstanding and Cheers mate.

Chris Rummel

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Would anyone be interested of a chart showing the wire colors on a R33 ecu? I have them all written down and was thinking about creating a PDF of it. I also have a legible-by-me-but-maybe-not-anyone-else wiring map of all the connectors that came on my R33 harness... like what pin on X connector goes to what pin on Y connector or the ECU, that I would be willing to put in some sort of digital format if it would help out.

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Cripes I can't believe it!!!


Armed with Chris's instructions, a simple multi-meter, a soldering iron, shrink wrap and a couple of short lengths of cable, I joined up the spaghetti pile that is my car electrical system.


I should point out that of the ten or so auto electricians I phoned up, only one came to look at my car and after seeing the spaghetti he told me that my particular job was not for him. He walked away quickly making a telephone sign with his hand against his ear saying "give me a bell if you get stuck with it mate". I was a particularly reluctant auto-electrician but I literally had no choice.


I was on my own with no 'good buddy' to help me or anyone else for that matter other than the Hybrid Z community.


The only company I had at all was my neighbours cat (yep we were dumb and dumber) that watched me walk back and forth with great interest and then tried to sneak into my house when it thought I wasn't looking - a distraction I didn't need!


To make matters more complicated, I put the GTR intank fuel pump in my new 260z tank and powered it up using the GTR fuel pump computer module & relay. (I cut the back off the vapour tank and used it as a plate to mount the computer and relay on)


So you can probobly guess that I was honestly ready for the acrid smell of burning plastic. I pictured myself on the phone ordering a new ECU, Loom, Injectors etc - in fact I thought I would most likely be ending up replacing everything electrical and sensitive to current.


What happened stunned me completely and utterly - I connected the battery, put the key in the ignition, heard the fuel pump spin and the swish of fuel being returned to the tank and then silence - I thought its probobly broken down! I went on to turn the ignition key further, then heard the starter turn and on the first go it just started - it didn't even turn over for any significant time - it just started like I swithed it off yesterday - how amazing is that - im still in shock!!!


This is all a complete ringing endorsement of Chris's thread.


If you are about to wire up your RB26DETT into a 240z and are worried about it, then my advice is stop worrying and trust this advice - with the benefit of this thread you CAN do it yourself - and it REALLY DOES work - I should know I just did it!!!


Thanks Chris

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I will have to agree it is a nice feeling to know you have accomplished something. After you complete something like this your next wiring nightmare will not so much be one! Everyone you do from here on out will be so much easier.. things you will see and notice.. its crazy. The engine harness of a motor is not that complicated if you know the few things about it and how the computer and sensors work. I have wired ka24e de sr20de det s13 s14 rb20 rb25 rb26 ls1 lt1 ls6 you name it and everything is pretty close as far as the basic things. constant 12v, switched 12v, start signal, injector power, o2 sensor and idle air motor power etc. Some people are just outright scared of wiring and state that the car will melt down if they touch it. I remember about 10 year ago when I was going to hook up an electric fan in my datsun 510. I hooked ground to battery .. well back then i didn't know you could just hook it to chassis because the chassis is grounded.. the power wire inside cabin into a switch and from switch to the positive side of the battery! WOW ... I soon learned after that a simple relay would do me so much better and well that switch for my fan would have had a happier life and wouldn't have been so hot with all that current flowing through it. Glad to see peoples wiring success stories. :)

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This post is designed to enable you to connect your RB alternator to your 240z. It contains ideas and data from all the other posts - of which there are many. If you don't fancy hours of playing the role of a forensic detective uploading and cross referencing many threads then this post is for you.


The RB alternator in this example is the standard R33 model - others could differ in terms of wire colour and if they do I will help you with that later on in the post.


The forum expert on this topic is Z Car Nut - Steve Golik and I thank steve for his practical advice to others around which this thread is based.


Connections - Your alternator will be earthed, have an 'A' terminal which sends charging power to the battery and have a 'T' shaped plastic plug containing two wire connections. One will be an 'L' connection which goes to a switched live i.e. it is only live when the ignition is on. The other will be a 'S' connection that is a voltage sensing wire that determins the alternator output. This needs to be connected as close to the battery terminal as possible and preferably directly to the battery terminal.


Wiring - Your choices are to either use the existing Z car loom or use the skyline small lower engine loom that came with your engine. There are a lot of posts that strongly advise against using a modern high output 90 amp alternator with a 35 year old Z car loom which was in its day only designed for a low output alternator.


Below is a pic of the plastic plug connector on the alternator:-




Top left, you can also see the insulated wire connector to the 'A'terminal.


There are two wires connecting to the plastic plug, white with red stripe and Turquoise with a red band.


I traced these to two plastic plug connectors coming off the lower engine loom near the starter motor as in the pic below:-






On my alternator the turquoise with a red band was the 'S' Sensing connection and so I cut this at the plug and extended it to the battery +terminal. The white with red stripe is the 'L' connection and I connected this to the hot when on connection, black with white stripe, in my old (73 240z) voltage regulator plug - see pic below. (You don't need an external voltage regulator any more so just unplug it, unbolt it and take it out).




The 'A'Terminal is pretty obvious and shown in the first pic, but it is easy to confuse the two 'S' and the 'L' wires that go to the plastic plug on the alternator. What if yours are different colours? Well, I read an old post by Zcar Nut who described how to tell them apart. Using a multimeter unplug the plastic plug and measure the resistance between each of the two connections and ground (you can use the alternator case as ground). The resistance between the 'S' terminal and ground will be significantly higher than that of the 'L' terminal and ground.


Now that you are all hooked up there is just one last thing to do. You must insert a diode between your 'L' terminal (white with red stripe) and the connection of it to the hot when on wire (Black with white stripe). The purpose of this with your new 90 amp alternator is to stop electric feedback which will prevent you from turning off the car.


Buy a simple N5402 diode from Maplin or Radioshack as shown in the pic below:-





It will allow current to flow only one way. Note the grey stripe on one end. Solder the end with the grey stripe on it to the wire from the 'L' terminal and the other end to the Black with white stripe wire that is hot when on. See pic below:-




Your alternator 'A' terminal will already be connected to the small engine loom so what I did was bolt this connection straight into a mega fuse holder and ran a lead from the other end direct to the battery +ve terminal.


Now check the voltage at the battery with the engine running. It should be between 14.4 and 15 volts.


If it is then hey presto you have just connected your alternator.


Just to recap here is a quick summary:-


-'A' post charging wire - to battery + terminal

-'S' sensing wire (turquoise with red band) to battery + terminal

- 'L' hot when on wire - to power source live when ign on

- Diode - wire in with striped end going to 'L' terminal


Please note that 260z & 280z cars are different and this post will only be of limited help to you.


Hope this helps.

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Well for someone that has little mech ability and or tools it will be very overwhelming. For someone that has a deep car background with lots of experience it will be easy.


It's not as straightforward as a l-28 turbo swap. but it is not the hardest thing in the world either.



Whats your background/experience with cars?

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1. Can I confirm that the "white connector" is only the larger white connector from the body harness as there are two inside the bracket pictured? I have traced all ECU connections to this larger interconnect and wonder if the smaller one can be disgarded.


2. It looks like the colours may be different on RHD Z's at the ignition switch, can anyone confirm that the black/white wire on the LHD Z's is blue on the RHD cars as pictured.


3. I only seem to have one relay near the ECU, not the "twins" in this tutorial, anyone know why that may be? maybe a series1/series2 thing?





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awesome thread!


cn i ask a really dumb question? (well i will anyway!).. how do you work out the block designators (ie. AF99, MA## etc..).. i have been looking for an R33 body wiring diagram, do you have one?


having things layed out as you have makes things seem so much easier (and almost seem achievable :))



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awesome thread!


cn i ask a really dumb question? (well i will anyway!).. how do you work out the block designators (ie. AF99, MA## etc..).. i have been looking for an R33 body wiring diagram, do you have one?


having things layed out as you have makes things seem so much easier (and almost seem achievable :))




Try this out ;)


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Chris couldnt find a straight swap for the water temp sensor in order to use the original Z gauge. Below from another thread the answer is now available


Originally Posted by getoffmyinternet viewpost.gif

I just realized today that Chris Rummel already discussed using the stock temp gauge for the rb swap. He confirms that the rb sensor will not work for the s30 gauge. Unfortunately he couldn't find the ohm specs on the l6 temp sensor, so he just used it and made an adapter hose to get it to work.


My hope is to figure out the specs of my l6 sensor and find an alternate sensor with the same specs but also the same size as the rb sensor so I can screw it into the stock port. If all else fails I can go his route, which isn't really bad at all.


Just got my RB25 in and running a couple of weeks ago. Ran into the same thing with the temp sensor, but wanted a more elegant solution than adding an aftermarket temp gauge or inline sensor. I usually have multiple projects going on at once, and for the first time it worked to to be a benefit. Knowing that Nissan crosses over many parts, I scoured the garage for a similar sensor. By pure luck, it didn't take long - I had a '91 240SX KA24DE on an eng stand, and sure enough the sensor matched size and style. Taking a multi-meter to it, it had the same resistance at ambient temp and the orig Z sensor. Lacking time, I went ahead and tried it out. Just as I hoped, it read just left of center on the stock Z gauge with the eng at operating temp. It even ran midway right of center one time when I forgot to hook up the electric radiator fan. The toyota one from Chris R's install article (LOTS of good info there) was too small in diameter and wrong thread pitch.

Hope this helps.


In the pic below starting from the left:

Stock '77 280Z, '91 KA24DE, stock RB25DET, Toyota one

Attached Thumbnailsattachment.php?attachmentid=9947&stc=1&thumb=1&d=1224788140




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So that all electrical can be found in one thread, I have copied this info into here



Mating the Z Gauges to the RB Engine Swap Sensors Etc

What a great combination of brains, knowledge, experience, and resourcefulness this site lends to us!!!!


Between all you of us we now have established:


Water temp gauge - Use S13 or R32 Skyline sensor Part No 25080-89903 if you have a motor from an R32 then it already has the correct sensor.

Oil pressure gauge - Use Z original sensor screws straight in

Amps/Volt meter - no change

Oil Temp Gauge - I used an additional water temp gauge fitted above the oil pressure gauge and used the Z original water temp sensor that screws in the RB20 sump. (see my website)

Speedo - use Navara D21 Ute mechanical gearbox Pinion Assembley Part No 3270202G17


Boost Gauge - Remove Clock - replace with Autometer Boost gauge, fits in housing. Just not sure where you link the gauge up to on the motor - anyone know?


Tacho - need some sort of resistance built for the tacho - anyone figured that one out?




This sounds like what is needed does anyone know if this would work for the tach? http://store.summitracing.com/partde...2&autoview=sku

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Mike, I can also say the R32 temp sensor works on the S30, I just finished my RB25DE conversion and used the original sensor that was in the manifold and works well; Just on half at operating temp and when it gets a bit hot under the collar, 3 1/4 temp! Also you answered a question I was going to ask about gearbox speedo drive; Navara D21...what year is that one? Now I almost have all guages working, just need my speedo! Tach doesnt matter; installed a shift light.

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Oh, by the way, hows my old 260Z? haven't checked your site for quite a while! Would love to see the finished product...




Hi Dimitri, I didnt realise it was you. I have moved to Bunbury and have the car down here. I have been travelling overseas every month this year so havent had time to do much work on it. However have the motor and gearbox in and am about to wire it up. Check the website



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