s5 tii swap to an s4
 

so i was looking first but couldnt find the answer to my question. i have the full wiring harness for the motor but i did not get the wiring harness for the inside of the car. can i just rewire my stock harness and just get the s5 clip that goes into the ecu or will i have to swap out that whole interior harness?

use your stock s4 engine harness. otherwise you have a rewiring headache

i cant re-use my s4 wiring harness. my s4 harness is n/a and i am converting to s5 tII engine and ecu. can someone just tell me please if the s5 wiring harness for all the interior electronics will plug into s4 cluster/ cluster surround, air controls and anything else that harness goes to inside the car?

you need your na harness and a s4 T2 ecu, pressure sensor, and air flow meter.

The easiest, most efficient, and cleanest way is to take the route Walken said, you'll need to use some s4 sensors as well as swapping your front cover for your OMP unless you want to premix. That's what I did anyways.

as far as the s4 air flow meter, sensors, and other electrical stuff is there gonna be a reduction in hp compared to s5 stats? i can still use the s5 intake manifolds and such correct? what would it take to convert to full s5 wiring? cant splice in the s5 interior wiring harness yellow clip to the end of the s4 harness?

no, you wont get a reduction. it will work out fine.

yes, you can use the s5 intake manifolds, but then you must use the s5 fuel rails.


to convert to full s5 wireing? s5 tps, s5 injectors, s5 OMP, s5 ecu, wireing harness, ON TOP of the things i cant remember.

DUDE, its a big monumental swap over for all the electronics. dont do it. the s5 will be nitpicky about things, go into limp mode, you may fry the ecu is the omp is possibly bad. just a whole headache that you dont seem to be capable of handling.

just save yourself the trouble, and follow what everyone else is saying.

i think i am capable of doing it either way, just wanted opinions on both possible ways. thanks for your help!

read my write up how to wire it in. i ran mine for 4 years like that, made 361whp 309ft-lbs on stock ports S5 hybrid turbo and 2.5" dp with a KS chipped ecu and afc neo so obviously it works perfectly and ran 11.8@119 after i streetported the motor no dyno # but definitely more power

, S4 electronics are garbage.S5 electronics they used on mazdas till 95, you can get the plug for the chassis harness from a mx3,mx6 probe gt.
you'll have to save the wires for you alternator when you strip the harness since they are in the n/a engine wiring harness, its alot more work doing it RR's way you have to switch the front cover and all the sensors

its not hard at all just take your time, i could do it all in a couple hours now

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/how-splice-s5-tii-engine-into-s4-chassis-703692/