hello, i have a friend who has a S5 with a blown motor and a S4 with a good motor that they want to swap into the S5. now i searched for quite a while and all the info was directed towards swapping all the externals from the blown S5 over to the good S4 keg. but they want to know if they can just swap the complete S4 engine/wire harness and ECU into the S5 car...they don't want to rip off all the S5 externals and swap them. they just want to install the S4 engine,harness and ECU. is this a bad idea? is it worth the time or should they find a good S5 motor instead of going through the trouble?

 

It can be done with no problems, but why. its a down grade of roughly 20 hp

 

I'm putting an S4 motor into an S5 right now. But I'm only using the short block and installing all the S5 stuff on it, IE, manifolds and front cover and OMP and all that stuff, that way I can use the S5 ecu still and have VDI. I wouldn't reccomend the swap, I'm just getting paid to do it.

 

False. S4 and S5 harnesses are completely different.

Really, their best bet is to put all the S5 externals on the S4 block and be done with it.

 

Its a down grade.

 

yeah they know its a downgrade but its one of those things where they have the s4 motor just sittin in a wrecked car and it runs really good and has low miles. thats the only reason they are even considering it. so what problems will they run into with swapping the engine/ecu and harness? will the other (body) harnesses on the S5 at the ecu, plug into the S4 ecu? i dont know much about the NA motors ive only ever swapped turbo engines..

 

There are a bunch of wires that will not mate up. you are talking about a potential wiring nightmare/hackjob all so that you can downgrade the motor. You know the s5's are heavier than the s4's right? When you put a motor with less output into a heavier car than it was designed for it will just make the car slower.

 

lol ITS NOT MY CAR I DONT CARE ABOUT THE DOWNGRADE ITS ONLY 14 HP...S4 or S5 they are both slow as ****..it really dosent matter

 

jesus...the wiring will not match up. end of story.

so either you spend hours digging through the fsm and repinning wiring harness...

or you do it the easy way and use the s5 keg with s4 peripherals.

rotaryresurrection.com has some good info on the subject. this question is asked about once a week. a simple search will also turn up more info than you need.

 

i searched..for about 30 min and all i found on here and on rotary resurrection was only info about swapping all the externals of the S5 onto the S4 keg when swapping them. but it sounds like its not worth it so ill tell them to forget about it and try to sell the S4 motor and buy a S5...

 

It's not a big deal really, the only difference is that the S4 has a lower compression ratio. The S4 to S5 power difference probably has more to do with ECU than the motor itself. When you swap all the externals, you get the added benefit of having all new gaskets for the manifolds and you can replace any vacuum lines and other things that may be worn out (assuming they're not going to try to half-*** it).