So over the last week I have been gathering information on this swap as I just picked up my first Rotary '88 RX-7 GXL. Im very mechanically inclined so tearing into something is not a problem coming from the Subaru WRX world. I need a little help though so I will list out what I have and what I've gathered thus far on the swap from this forum and reliable sources. My questions will be at the very bottom of this post.


***My goal is to get the car running as reliably and close to stock as possible with the parts that I currently have on hand. If anything else is required, I will purchase them. ***

Background on car: 1988 Rx-7 GXL

Parts I have:
- S4 engine and trans (blown coolant seal)
- S4 intake manifold with sensors and exhaust pieces
- S4 ECU (no added engine management)
- S4 everything else is S4 related
- S5 engine and trans (working)


1- Can I use the S4 intake manifold with sensors on the S5 motor? (If so, question 2 applies next lol)
2- I read the EGR port on the S4 is on the block itself but on the S5 its on the intake manifold. I want to rid myself of it anyway, so with installing the S4 intake manifold to the S5 block, do I not need to worry about it and is there anything else that needs to change on the electrical side?
3- I plan to delete the rats nest as its all cut up anyway could this pose a threat to the OEM ECU?
4- I am keeping the air pump for now since the exhaust will be stock form and I dont want to buy extra pulleys and belts.
5- Ive read that I do not need to swap the S4 front cover to the S5 if I block off the OMP and run premix (which I planned to run anyway per other resources Ive read), what else am I missing to make this swap work as close to OEM as possible with getting rid of stuff not needed?

Sorry for the newb questions as Ive only had this car 4 days lol. I just want to consolidate my findings to one thread.

 

Yes, with modification. The main difference in the blocks will be the port-air passageways through the lower intake manifold. There used to be a good link on manifold swapping S4 -> S5, but the point is one has the ports on the outside and the other has a single port in the center. I *think* the S4 LIM will cover the gaping hole in the S5 block, which basically means you'll never pass an emissions test. Otherwise, the car will run fine. The S5 LIM could be used, but modifications to match the bolt pattern on the S4 UIM.

The best route would be to keep the whole S5 intake manifold setup and use the S4 throttle body. You will need a way to make the VDI system functional, but that can be done with an RPM switch and the stock air pump. Search threads under my name for a write up.

S5s have no EGR valve. It's the S4 TIIs that have it on the LIM. This could be an emissions problem if someone goes looking for a non-existent EGR.

Just be careful what you remove. Many novices end up with idle problems because they just rip it all out. The manual or colorized vacuum diagrams on the forum / many emissions removal threads will help.

Tap into the air pump to run the 6PI (aux. ports) and VDI (variable dynamic intake) systems.

If you're using S4 electronics and wiring, the S5 cover can stay. Just remove/block off the MOP if you'll be using premix. If you want to use the S4 mechanical MOP, swap front covers and adapt the linkage to work with the S5 intake manifolds.

 

3.nothing if going to effect the stock ecu just get the block off plates to delete the rats nest.
4.you can also take off the air pump and still use stock pulleys u just might need a new belt.

 

Thanks a bunch RotaryRocket88! This clarifies a majority of my hold ups. I just need to look into the rats nest removal now to make sure I do it properly.


I did read something about a yoohoo belt and found it out on pineappleracing. Ill keep it on for now as my knowledge of these cars is only a few days old.

 

This looks interesting. Id rather use this if it works vs premixing every fill up. Anyone have experience with it?

Oil inject. Pump Adpt

 

Nice Bling..
But if you think about it you still have to fill up the container..so why pay the money for a fancy container?
Maybe it's just me,But since I am at the gas tank,I can exert the extra effort it takes to lift a 16 oz 2 stoke bottle and pour that into the tank too...Really,you put gas in,..it's like a habit..

 

My thought process is if it works as it should just like when its stock, then it would be better than filling up and remembering to put the oil in the gas tank. Just looking to simplify the process and I'm more interested to hear whether or not it works. I apreciate your .02 cents though. If it turns out to be just "bling" then i will pass on it.

 

id like to kno how the swap turned out! im going thru the same swap with my 88vert..