I am switching to s5 irons for my new build, and the ports are larger than what are on the s4 manifold. My options are to port match the s4 or to get the s5 LIM and UIM. I would like to keep my s4 OMP, so can I install an s4 turbo TB on an s5 (jspec in this case) upper and lower intake manifold? premix is annoying. I guess I could port match the s4 TB to the s5 UIM if I have to. I think porting is unavoidable, but I feel that s5 manifolds will flow better than ported s4 manifolds.

This is on a 400+ rwhp build btw, race gas on a T04R.

 

btw the s5 irons I have are jspec (not sure if they are different or not). I read on ReTed's site that the s4 ports are bigger, but I am referring to the runner section of the port, which appears to be significantly larger on the s5.

 

i have the same conversion. i used an S5 block with complete intake and a S4 throttle body with omp.

 

^ were you using jspec s5 T2 manifolds? is the brake boost plumbing different?

 

i'm using a s4 t2 block with jdm s5 t2 intakes, s4 t2 tb.

 

^ my question is, are there any major vacuum plumbing issues from using the JDM intakes? I am also going to be running a KG secondary rail.

 

The S4 TB will work on the S5 manifolds,you need need to un screw one of the studs a little bit so the nut will grab the threads if that makes sense.

 

what does the fuel rail have anything to do with vacuum lines? i dont have any "major vacuum plumbing", maybe 5 lines total in the whole engine bay.

 

I'm sorry, fuel rail is plumbing but it is not vacuum plumbing, I wasn't trying to imply otherwise.

I just didn't know if stuff was different on the JDM manifolds because they are designed for a RHD car and they are designed for different emissions specs (although I know that none of the s5's had EGR).

and ^^, I appeciate the heads up, I will keep that in mind.

 

I run a s4 throttle body on my S5 motor

 

yea actually the brake booster line that goes into the intake is facing the wrong way. it's just a banjo type hose fitting, you can unbolt it and reclock it and use a longer hose.

 

i removed all the emissions crap so if you are trying to keep it i wont be of much help. there isnt a problem or any real issues running the jdm manifolds...at least in my set up that is.