Hypothetical situation that may or may not be a reality in the near future:

I have an S4 TII and an S5 TII motor. when swapping is there anything that the S4 has thats better? or interchangeable with its S5 counterpart (i figure why not plan on breaking things, itll happen)? and, point of clarification, im not asking for anyones opinion as far as whether or not i should do the swap.

 

HIgher compression, reinforced rear iron

 

you should get a whole S5 longblock, harness and ECU to make it smother. i'm sure theres gunna be more complications, i just can't think of it right now........

 

the s5 housings have better spark plug placement i'm told
other than the higher compression on reinforced rear iron i'm not too sure

why isn't the rear iron stronger on s5's?

 

i just shipped my SP s4 block with s5 e-shaft, s5 rotors(higher comp, and lighter!!) and s5 counter wheights, should but what you would do, if your planning on running a EMS,. which i will switch too when i get my new turbo put on.

 

also i heard something about the upper intake manifolds? is the S4 better?

 

s5 is better it has longer runners for intake mannys that means more torque, the s4 rotors are better if your going to run higher boost and the pound will not make a diffence because youll hit your limit before the light rotor matter. s5 irons s5 intakes s4 rotors and housings is my set up i tryed to get the best of both s5 and s4.if its is an s4 keep the s4 TB and it will make things easyer. and remimber you have low emp injectors so dont get that mixed up.

 

Should I buy more low impedance injectors or remove the...idk the pack that requires the low imp injectors? I plan on having my 550's cleaned for primaries and 720cc secondaries. I will be using either an Rtek 1.7 or MegaSquirt.

 

if using a s5 engine in a s4 car, if you got a long block of both, u will want to use s5 manifolds, but bolt your s4 throttle body onto the s5 manifolds.... and use the s4 electroincs and wiring u had... then either run premix, or swap your s4 front cover and omp onto the s5 block... then id prolly do emissions removal to simplyfy the setup........ use the s5 intercooler if you get it.. the s4 one requires a lil "tweaking" to fit ontop of the s5 manifolds....

if using the rtek id just buy some low imp 720cc injectors... that makes it most simple no rewiring needed then,( assuming u do have that stock resistor pack u mentioned)