S4 RX7 TII to S4 (stock) wt/S5 hybrid turbo and manifold
 

Hi, im rebuilding my Rx7 from ground up, my shell is a 1991 rx7 na, i have a complete S4 TII for part, and a S5 bloc with turbo and manifold, both turbos doesnt have the same manifold to turbo flange, as my S4 is square and the S5 is not, looking at the S4 manifold ive noticed the actuator wich the S5 manifold doesnt have, my question is this, if i use the S5 manifold and turbo, wich bolt on directly to my S4 bloc....already tried...what about the actuator ? I have looked on several post and books like haynes and chilton but i cant have a detailed plan of the exhaust and manifold of the S5...only earlier S4...ive noticed many guys have did this...S4 to S5 turbo but it seems like later S4 and earlier S5 have the same flange...am i rite ? any and all help appreciated Zoom zoom to all !

You can't use an S5 turbine housing with an S4 exhaust manifold, or vice versa. The S4 and S5 flange styles are different, and can't be mixed. The S5 uses a fully divide manifold w/ equal size runners, and the S4 uses an undivided manifold w/ unequal sized runners on the turbine side. The actuator closes off one runner at low RPMs to improve spool. The S5 design is superior, so use it. Everything bolts on fine & you can reuse all of the S4 oil and water lines.

S5 turbo on my S4 engine:

https://www.rx7club.com/picture.php?...&pictureid=521

I must have made a mistake while explaning my problem, i have a 88 turbo II S4, my turbo is done, i want to swap my s4 turbo and manifold for my s5 hybrid (h13 t3/t4) with the s5 manifold...my problem is with the actuator in the s4 manifold...but if you say everything bolts on fine it shouldnt be a problem...

Sorry...i forgot...thanks a lot for the reply...

I understood you. You don't need the twin-scroll actuator if you're using an S5 turbo and manifold.

Ok, so i just delete the line that goes on top of the actuator of the s4 manifold ?...do you know if theres any other parts, like injectors, units...beside vacuum lines and such that i can salvage from the S5 bloc to rejuvenate my S4 ? I just dont like good parts going to waste and i have both engine sitting side by side.

Yes, you can remove the hardline and the twin-scroll solenoid on the rack. Cap its vacuum source off.

As for other things you can take from the S5 engine, there isn't much else that's worth taking.

After further research...i read that i could remove the front cover and omp from my S4 engine and put it on the S5 and use my S4 electronics and ecu to run my S5...i have a list of all the parts i need to change on for the S5 to work, the TB and cable, injectors (since i dont have the S5 harness i cant change the plugs) dash and engine harnesses, ecu, all sensors, maf tps ect, TII diff, half shafts driveshaft and tranny and cylinder, is that rigth ? Im runing a big turbo i guess (see pic) its a hybrid h13 t3/t4...its twice the size of the oem...so im pretty sure its better to use my S5 since its in way better shape then my S4 wich i drove for years...

You will run into problems trying to mix and match S4 wiring/electronics with S5 chassis wiring. They're very different. It is always better to keep everything matching.

I hope you're planning on fuel injector/fuel pump/engine management upgrades with that turbo. The stock fuel system will not handle a hybrid of any size. If the turbine side of that turbo is unaltered, it would appear to either be a T04b H-trim compressor of a 60-1. Power levels would be in the 300-350 whp range.

Sorry to bring an old thread back from the dead, but I have a chance to grab a low miles S5 turbo and manifold for very cheap and I'm wondering if it will swap right into an S4 T2? What else will I need for it to work properly? Anything else that needs to be done besides taking out the S4 turbo and mani and bolting in the S5 ones? Will it boost properly?

Ya,it will work.
You may need the oil return lines.The metal tube in between the engine and the main return line are a bit different.So just grab all associated lines,oil and coolant and swap it out.

what about the stock electronic boost controller that is present on the S5's that raises boost to 7.5-8psi (IIRC the stock wastegate spring is set at 5.5-6psi, correct?...)?
Can that be transplanted into an S4 without too much of a hassle? Or does it require an ECU/harness/etc. swap as well?

The s4 Ecu does not have an output to control the boost solenoid. In order to use the stock s5 system, you'd need the s5 ecu, maf, pressure sensor, harness modification etc. Just get a boost controller.

Oil drain line stays S4 if bolting an S5 turbo up. It just has to match the front cover.

Thanks for clarifying that RR...That is why I said "may need".
I have changed my setup so many times I should have "snaps" on my engine instead of Bolts!