S4 to S5 Swap Wiring Harness Question
 

Hey I am planning on swapping an s5 motor into my s4 rx7 na and have a question about the wiring harness. I have almost everything I need for the swap like coils, ecu, the main wiring harness. I just need an s5 maf, and I've heard I need to get the wiring harness that is in the dash for the swap to work. Is this true? Or can I just use the wiring harness that is in the dash already (s4).

Thanks!

keep your s4 wiring and you wont have the inferior s5 failsafes.

Do you mean keep the s4 harness in the dash and then run an s5 wiring harness for the engine?

Wire the S5 engine with the S4 engine harness that way you dont have to rewire the car and you can use your MAF thats the easiest way. You may have to change injectors also. I'm not sure my car came hi Imp. so I could use the stock S5 injectors minus having to short the thing together on my swap.

So you're saying use the s5 block, and then put the s4 parts onto it such as intake manifold, throttle body...?

keep intake manifold they flow better just the T.B. cause of the TPS is different.

You can bolt on the S4 tb and tps, that would be easiest. Although you can use the S5 tb and tps also. There are two separate barrels for the S5 TPS, a wide range and a narrow range, just wire up the narrow range.

http://homepage.mac.com/carldavis/intake.html
Is more or less what they're suggesting you do.

I know it's possible to install an S5 ECU and engine wiring harness, but I know no details of how to do it.

Also my s4 block is blown which is why I am swapping. There's no point in even trying to rebuild it since I blew coolant seals, apex seals, and warped almost everything inside the engine. She got REALLY hot and I didn't realize it. So hot there was smoke pouring out of the oil cap and the dipstick when I pulled that out. So I was just planning on putting the s5 motor in it. The only thing stopping me from doing it is I am not sure if I will need an s5 wiring harness from the dash to go with the s5 engine harness, or if I can just use the s4 dash wiring harness with the s5 engine harness.

S4 to s5 wiring harness swaps only require the maf and maybe the TPS to be changed. S5 injectors can be run with an S4 ecu and harness while S4 ( low impedance injectors ) cannot run on a s5 ecu. You do not have to change the dash harness or the internal chassis harness. These are all the same minus the output for the boost gauge in the dash.

Alright thanks for your help, I have everything for the swap (s5 ecu, s5 wiring harness, s5 coils, s5 injectors, s5 maf...) I just was wondering If I needed the s5 harness in the dash to do the swap so since I can keep the s4 harness in the dash I'll go ahead and start the swap.

I just got done cleaning my S5 engine and tranny that I bought for this same swap

:icon_tup::icon_tup:I have the S5 complete engine and tranny still bolted on, S5: ECU, coils, and an extra S4 harness to mangle if I have to. I'll def be watching and posting on this thread the next couple weeks. oh and I'll have an extra turbo in good condition if you think yours is bad, it has about 40k on it...

Well I don't need a turbo since I just have an na. I did a little more looking and on rotary resurrection (http://www.rotaryresurrection.com/2n..._s5_diffs.html) and I found that the dash harness and the engine harness plug into each other as well as into the ecu. (Shown in step#2) I am wondering if an s4 DASH harness will plug into both the s5 ENGINE harness/s5 ECU. That's all I need to know

Thanks!

no they dont thats why I said use the S4 harness!!!

Well I'm confused cause I got both answers haha, you said no and S somethin fd said I don't have to change them

bump

The harness on the engine is called the EM harness.

The EM harness whether series four or series five, plugs into the FRONT harness.

A series five EM harness will NOT connect to a series four FRONT harness. Unless major rewiring/repinning of the Front harness in the series four is done.

Series five ECU will NOT plug into a series four Front harness nor a series four EM harness.

A series four EM harness will not control the TPS on a series five engine nor the electrical plug of the OMP on a series five engine.

A series four ECU will not control the VDI on a series five engine not the solenoid on the series five engine that controls the auxillary port actuators.

THANK YOU! Finally the answer I was looking for. It would've been easier to search if I had known what the harnesses were called. Looks like i'll be putting the s4 things (throttle body, intake manifold, injectors, bla bla bla) onto the s5 block and just run it using the s4 ecu and harnesses. It's not the best option but I'm fine with it as long as it can get me around long enough so I can save up and swap a 350 into it. :egrin:

DO NOT swap for a 350! :P

Also, go back and read the website I linked about using the S5 intake on an S4. You should totally do that! VDI is awesome. ^_^ Notes: You'll need: those two RPM switches, an S4 front cover with OMP, and an S4 throttle body. The only things you'll have lost [compared with a full S5 setup] with this setup are: the improved OMP efficiency and the extra 1K RPM limit.

Told you stay series 4 its easier. its not worth the pain of body wiring. Especially if you ever plan on blocking off the OMP. If you tried you would have to chip the ECU so you dont go into open loop from the OMP! S4s are so much simpler to deal with even Turbo swapping.

Sorry about the mini thread jack but it is related: my swap is the TII S4 to TII S5 engine. I have the ECU and complete engine and transmission. What is the best way to wire this swap into my S4? I have a spare S4 harness to cut up too...

I knew I was going to get some hate for saying that haha. The rotary engine is a great design/idea from mazda, and I have nothing against rotaries. They just have lots of issues that I don't have time for so a 350 swap looks like the best option for me. It's a cheap build to make almost 300 hp in a 2600lb car while keeping the weight distribution close to 50-50. As for the VDI thing I've looked into it and if I have the time I think I'll go ahead and give it a try!

If I had a series four turoII engine and transmission, and I wanted to remove it and install a series five turboII engine and transmission..................I think I'd leave all the wiring stk series four. To most of us the big problem of putting any series five in a series four is the OMP which is electrical on the series five and this problem needs to be overcome. So I'd remove the front cover and OMP of the series four turboII engine and put it on the series five TurboII engine that your about to install.

But then you'd still have a OMP problem in that the series five throttle body does not have provisions for the OMP control rod that connects b/t the OMP and the throttle body.........so swap the series four throttle body with the TPS also, on to the series five engine your about to install.

Remember the series five TPS is a two pot TPS and the wiring is quite different b/t series so I mentioned that just above.

I and many others could modify the series five EM harness to match the series four Front harness where I could just install the series five engine and EM hanress along with the series five ECU but that would take quite a bit of time, soldering and figuring out the diff b/t the two series harness by looking at the free online wiring diagrams in order to do so. Just saying it can be done and has been done by OTHERS and I know I can do it but I won't even try to do it for anybody else for free. The plugs b/t the two series will never match and that accounts for my mentioning "soldering"/splicing etc.

And after you modified the series five EM harness to match the series five front you'd still have to take care of the OMP differences. I think this sentence might be redundant. Oh well. Time to go.

Another way to see what your up against..................uncover the present ECU in the car. Now hold the new series five ECU up against that series four ECU. Notice how the electrcal plugs won't fit? Plus there's one or two other orange colored plugs in the foot well that mate the EM harness with the Front harness and notice how they won't mate b/t series.

since you have a extra harness, rewire the S5 and use the S4 throttle body and TPS and your done just make sure the injector are the same imp. You'll be good or you might have to mod the harness which is simple to do.