WILLSMAZDARX7

i was woundering if any one knows how hard it would be to put a 1990 gxl n/a into a 86 n/a i've done swaps in the past but the same year motor , i would asume i would need to change the computer near the passenger floor but is there anything ealse ?

'87 turbo II

iTrader: (1)

I know you're going from S5 N/A to S4 N/A so it shouldn't be too hard. Replace any CPU related pieces you're getting out of the GXL too. The 5th and 6th ports on an S5 are electrically controlled S4 is vaccume hose opened.

Aaron Cake

iTrader: (1)

Actually it's a MAJOR pain in the ***. Between S5 and S4, nothing is the same as far as wiring. Dash harness, body harness, emissions harness, engine harness...They are all different.

If you are going to do this swap and use the S5 electronics you will need to modify each wiring harnes to meet up with the ECU. When I do something like this, I basically end up remaking the harness so that the engine harness is totally seperate from the rest of the car. Give it 12V and ground...Those are the only two connections to the car's electrical system. But that's a major project.

It's much easier to take the S5 block and simply swap it in place of the S4 block, keeping the S4 manifolds and electronics.

WILLSMAZDARX7

so i can take the s5 block and bolt on the s4 parts ? does everytheing bolt up the same way ? and will i still gain the little hp , reason for the swap is that the s5 motor runs perfect and i want to be perpaired when the s4 motor goes

RotaryForce13B

Yes everything will bolt up the same way, just like Aaron said. Use the front cover, intake, water pump.......blah blah blah from the S4 and put it on the S5 block I don’t know about gaining any hp. the hp gain from S4 to S5 was from higher compression (lighter weight rotors) and the intake. So, if you use S4 goodies on a S5 block I don’t think you see much of a gain.

BlackLabel6542

dont mean to jump in and change the subject of this thread but I am swaping an S4 motor into my S5 vert because its what i've got. will the same work for me? bolting the S5 "goodies" onto the S4 block. thanks for the info

topspeed7

like rotaryforce13b said if you guys are changing the s4 motor for a s5 because of its mechanical features its better to just stay with the s4 electrical system and just change your front cover on your s5 and install the s4 cover(because of the oil metering pump)and run a s4 computer trust me ive done it and its not worth changing the electronics. and with minor harness mod you can use s5 intake manifolds(better flow)

WILLSMAZDARX7

hey guys thanks for the help but about the minor wiring mod to use the intake plz let me know if you can give some feed back