ok my friend bought a lemon from a member of this board which will remain nameless. It is a S4 TII and it seems like every jspec shop on the net only has S5 swaps so he ordered one. It is the complete motor, tranny, ECU and uncut harness. Now my question is which would be easier for us, keeping in mind that his S4 engine harness is shot to hell.....
1) Would it be easier for us to try to mend the broken harness and swap all his s4 **** over which seems like a **** ton of work
OR
2) Install all the S5 crap in and from what i heard the dash harness connector to the ECU is different between series and rewire that at the ECU
Im leaning towards number 2 since we can reuse the S4 tranny since the crossmember to the S5 is different

I know the s4 NA and the S5 TII have different dash harness connectors....are TII's different as well

 

strip the s5 motor down to the keg and use as much s4 stuff as possible on it (except you should use s5 intake manifolds with s4 TB). find a good condition used s4 T2 engine harness. this will have the least likelihood of electrical gremlins

 

that just seems like too much trouble.....maybe we can find a good used dash harness. other than the ECU plugs, the dash harness is the same right???

 

No, basically all the plugs are different. Just find an S4 TII motor or put all the S4 stuff on the S5 block.

 

It ain't a Dash harnes. It's called a FRONT harness and is composed of everything RED in the attached jpg. In other words runs inside the car from right to left, leaves the interior compartment to the engine compartment and goes fwd on the left side then across the front of the car to the right side of the car.

That FRONT harness of a series five won't mated with a EMISISONS harness of a series four nor the ENGINE harenss (colored BLUE in the jpg) on the left side of the engine bay of a series four, nor with the Instrument harnesses of a series four.

 

trust me man, this forum is littered with s5 swaps into s4 cars, gone horribly wrong. it makes even less sense to put s5 T2 electronics in an s4 car. The s5 oiling system is less reliable than the s4, you don't need the s5 boost control solenoid, and the s5 T2 ECU's are expensive and hard to find (JDM ECU's don't work well).

All the important advantages to the s5 T2 are contained in the shortblock sans wiring: lighter rotors with higher compression (some don't like the higher compression), superior rotor housings, and different shaped ports. put an s4 front cover and s5 intake manifolds (with s5 turbo and manifold if you have a good one) on there and run it as an s4 car essentially. Yes there are a few more details to it that I probably don't recall right now. Remember it's not like s5 n/a cars that have the VDI system and such where you might be more inclined to want s5 wiring in an s4 car.

 

true....i appreciate the info. looks like we will be swapping parts over. thanks Hailers, youre the man and arghx for showing me the light haha

 

you can use s5 electronics in a s4 pm me for the info i documented everythin if you have sufficiant knowledge of soldering and can followeasy intructions you can wire and start the motor once it's in the car in an hour at the most. now s4 electronics in an s5 thats a headache you gotta run new cas wiring and make sure it's sheiled or pull the cas wiring out of an s5 harness.either way it can be done and if your tight on money or time it gets the job done.btu if you just wat to swap manis over and supporting electronics thats the easiest way.

 

Hello I am doing some what the same thing I have a 87 s4 rx7 non turbo that I am putting in a 89 s5 turbo II motor but I am using the Haltech E8 instead of the s5 ECU that came with the motor. So I will have the s4 FRONT harness will I need to change it still? And what is differences between the s4 and s5 transmission mount my s5 turbo II motor came with the cross member it looks like it would bolt right up to my car.

Thanks

 

If you have the S5 trans cross member then youre good....the s4 and s5 have different mounting points on the crossmember. and yes the FRONT harness will still have to be changed or soldered to fit bc the front harness and the engine harness are two different things

 

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Take him up on it and have a go at it.

 

I already pm'd him...no reply yet but im curious to see what he did