I was wondering what intake manifold would bolt in into a 87 S4 motor? i was wondering if 3rd gen, woud fit S5, and laslty the cosmos Manifold. The real ? is about the 13B RE manifold since i like that one the best.

 

Technically they will all "fit".

 

Omixeo is right. From easiest to most difficult to convert to fit would be: S5, FD, Cosmos, and I only say Cosmos because I haven't seen many people try to fit that on unless they were doing a complete motor swap.

Wait, is this turbo or N/A? I'm assuming turbo, but if N/A then you've also got to worry about aux port and VDI activation.

 

Right, becuase the Comso LIM has the Aux ports in there you just need to worry about the activation.

The answer is the only manifold that will fit an S4 is an S4.

The real question is WHY? I'm going to say you're looking to do this for aesthetics ONLY because of your comment, "I like that one best." Let it be known that they will not fit and frankensteining crap like this together hurts performance. You think Mazda designed the mani's to look pretty? Do you have any clue how the VDI or the AUX ports work? Do you know about port timing and reversion? These are all things that you should learn before swapping parts and making less power. Search more, ask less

Oh - Thread of shame for you too - https://www.rx7club.com/showthread.php?t=707133

 

Mazda spent alot of money on researching and designing the intake system for all the RX-7's. Keep it like it is.

 

There is a writeup on switching S4 NA manifold to the S5 NA manifold, search for it.

The inlet ports for the RE and REW are in a different sport, so they will not work.

 

Apparantly there is a gain of swapping an s5 mani onto an s4 block, I'm going to do it myself since I have the parts and its not all that hard, we've got a dyno around here too where I can actually measure the gains over stock.

 

The best upgrade is a Weber type racing manifold with individual throttle bodies. The Holley type would also be an upgrade. I don't see much point in slapping a different stock manifold on your engine unless you just want to be different and pretend that the engine is more powerful because of it.
http://www.mazdatrix.com/r-idamanifolds.htm

 

It has actually been proven on a dyno that the s5 manifold nets 10+ hp over the s4 manifold due to the VDI. Considering the lack of cost-efficient alternatives, this is an excellent mod for an s4 NA engine.

 

Yes it is a 87 Turbo S4