Zero10

I am preparing to megasquirt my S4 RX7, and since I will have the ability to control some extra things I figure this would be a great time to swap an S5 intake with VDI onto my S4. I have done a ton of searching and unfortunately pretty much everybody just links one write-up and says "this does a great job explaining it", however that site is down (and has been down for a while) leaving me with very little to go on.


I found this thread:
https://www.rx7club.com/2nd-generati...-im-s4-256577/

Where Icemark indicates that the best bet is to swap the S5 UIM onto an S4 LIM, do the necessary grinding and delete the EGR. After doing more reading and being unable to find any pictures I am left wondering a few things that I was hoping could be answered (keep in mind I am doing a full engine re-wire and megasquirt conversion):

When I remove the EGR do I just need an EGR blockoff plate? Is there anything else required to seal it up properly?

Can I keep my S4 front cover and adapt the S4 OMP to be driven from the S5 throttle body somehow? Will I be able to use the S5 TPS if this can even be done?

There is mention to remove the rear stud on the S4 LIM to allow the S5 UIM to seat properly - won't that risk introducing a big vacuum leak as that part of the manifold is no longer clamped down?

If I get an S5 UIM and throttle body will I also need the snorkel tube and airbox?

Can I use the S4 fuel rails?

I am hoping to switching to disc type injectors such as the yellow RX8 injectors since my stock injectors are very very plugged - will these fit S4 rails and S5 UIM with S4 LIM? I was hoping to delete the air bleeds as well.

Sorry for all the questions, normally I'd try to just pick up the parts and start figuring these things out, but I can't even start the project until after June 22, and I only have until mid August to finish it so I'd like to sort out as many details in advance as possible.

For control I am planning to mod the air pump to provide air pressure to the VDI and aux ports through solenoids controlled by the megasquirt.

RXSpeed16

iTrader: (41)

Just did this recently with the intentions of keeping everything, including emissions, functional. Also agree that everything documenting it is gone.

My parts list: S4 intake tubing, S4 TB, S5 upper intakes, S4 lower, S5 rats nest, S5 fuel rails, S4 injectors, S4 harness, S4 BAC with modified plug for clearance between it and the fuel rail.

A blockoff plate and a little RTV is all you need. I pulled the stud and used a bolt instead to gain clearance, but I do not think it was necessary. And block off the line from the control solenoid. I went with a S5 rack and rats nest since it fit better with the upper intake.

I used the S4 tb. I "adapted" the rod on-car with vice grips, pry bars and many large swear words. Can't say exactly how to do it with an S5 tb.

^That's what what I did. It clamps down and it seals fine with gasket and a little RTV. More than I usually use with a gasket, but not a lot.

I used all s4 intake tubing with my S4 TB. I believe they are they mount up the same, but you may want to check that. Had to deal with the air line that normally feeds the BAC and AWS, but I removed the AWS and the S5 BAC is right under the intake tube. Also needed to figure out a way to feed air to the omp injectors. I removed the S4 plastic spider and used the S5's metal spider fed by the port previously used to feed the AWS.

Nope. You need S5 rails. I kept my S4 injectors though.

Dunno.

I'm planning on doing the opposite. I'm routing some exhaust pressure through an unused tube in the rats nest and putting the RPM switched solenoid on the solenoid rack. Leaving exhaust backpressure to decide when to open the 6-ports. Ironically, getting the VDI working is the single biggest reason to do the swap, I've just haven't gotten around to finishing it yet.

Zero10

Thanks so much for the answers!

Keeping more of my S4 parts will make the swap cheaper when an S5 finally turns up at a local junkyard so that is nice. I was hoping not to have to swap the fuel rails but I suppose that is not a big deal. I don't know how the rails differ so I'll do some research on that right now. I heard the yellow RX8 injectors are a direct swap for S4 N/A injectors (450 vs 460cc is pretty close and I can tune that difference out) so if you kept S4 injectors I'd imagine the RX8 injectors will also fit and since I'm running all new wiring the connector difference is no big deal.

I didn't know I could re-use the S4 BAC and throttle body. That makes the swap easier later I think!

I hadn't considered the air source for the oil injectors - good to know it isn't super hard to deal with.

I'll be repurposing the EGR control solenoid to control the VDI so that part isn't much trouble, and there is another solenoid down there that I am hoping to re-use to control the aux ports. I forget which one it is as I don't have my notes in front of me right now.

I have to modify the split air / air control valve system a bit since I believe with the electrical bits disconnected but vacuum connected it will direct air to the ports, but with vacuum disconnected and electrical disconnected it directs air to the split air pipe. I think that is the scenario I am looking for, I might just have to try various things until I get air directed only to the split air pipe, or just cap the fittings and dump the air to the atmosphere. I'm not sure, but I can't have it going to the ports as that is injecting the air pre-O2 sensor and will mess up my wide band readings.

farberio

iTrader: (7)

The pics are broken, but this will get you to the page.

89 Intake Swap Introduction

Zero10

The wayback machine! How did I not think of that?

The guide is still somewhat helpful without the pictures and has continued to help me plan this swap. Thanks!

Unfortunately I found an issue with the RB cat delete pipe I had picked up and I need to source a new one before I can move ahead, it sucks but it's not a show stopper.