Zero10

I am currently stocking up the parts and getting ready to megasquirt my S4 FC (1987 Canadian GX model). The car is very stock (engine-wise) right now (I have already fitted a WBO2 but that's it) but when I megasquirt I am planning the following mods:

Yellow RX8 injectors (my stock injectors are badly plugged and I hear these are disc injectors that will let me delete the air bleeds and are just as cheap as stock injectors)
S5 intake with VDI (still shopping around for one of these, I might make the switch post-megasquirt if I can't find one soon enough)
Racing Beat catless downpipe and resonator (I already have this just need to swap it on)
Deleting the aux air solenoid and removing the coolant lines from the UIM so that I am just using the BAC valve for idle control.
Deleting the extra set of throttle butterflies and thermowax and other associated hardware from the throttle body

Given that I am planning on swapping an S5 intake on I was planning on modifying the air pump to supply air to the aux ports as well as to the VDI by doing something very similar to this:
https://www.rx7club.com/2nd-generati...itches-907824/

Except instead of RPM switches I plan on using 2 of the megasquirt outputs (suitably protected of course)

To simplify tuning and monitoring of the engine I would like to modify the split air / port air system to do one of the following:

Completely delete it, but still retain the stock air pump to help drive the water pump and control aux ports / VDI

Reconfigure it to always direct air to the split air pipe - this should be safe since there are no cats to overheat. This way I don't have all that extra clean air messing up my wide band readings.

I found this thread which talks about the operation of the split air / air control valve:
https://www.rx7club.com/power-fc-for...nniing-882668/

However I'm not 100% sure if the operation of this valve is the same with the S4 as the S5 and which one the factory manual sections are taken from.

Can I simply remove the vacuum lines from the split air / air control valve and have it always dump air to the split air line?
Can I delete the valve altogether and just add some kind of restrictor on the outlet of the air pump so I can get enough pressure to operate the aux ports and (later) VDI?

Am I missing some other horribly obvious solution?

I have a MS1 V3.0 that is completely assembled ready to go in if that matters.

Thanks a ton for any help!

Aaron Cake

iTrader: (1)

Unless you have replaced the air bleeds with something, you still need them when using RX-8 injectors. They are what the injector seals against in the block. They also perform a very important function, regardless of the injector used, to help atomize fuel at low airflows. In fact Mazda has continually improved the air bleeds over time and in the RX-8 they actually consist of small pipes that blow directly onto the injector inside the port runners.

OK. You can also lose the dashpot as the 'Squirt can use the BAC to emulate one via software.

You don't need the split air pipe at all, nor the ACV or any of the associated plumbing. The output of the air pump can be directed to a small manifold which can supply air to the solenoids. Then attach a check valve to the manifold to dump extra air after it reaches a few PSI.

I've always though a far more elegant solution to port activation was just run a small CO2 bottle in the trunk regulated down to 2 PSI, then use solenoids to apply that pressure to the actuators. A single smallish CO2 bottle may last a year or more.

Check to make sure there are enough outputs as the MS1 doesn't have too many spare. Aside from that it's an OK ECU but VERY old and very limited compared to MS2/MS3.

Zero10

Thanks so much for the answers.

I forgot that the air bleeds act as spacers that the injectors sit against. I'll keep them in there then! Any thoughts on the RX8 injectors themselves? My stock ones are VERY plugged up and spray terribly, and injector cleaning here is expensive enough that it is cheaper to buy reman RX8 injectors.

I'll be tossing the dashpot and removing the coolant lines from the UIM to help simplify things.

I see lots of people talk about deleting the ACV and replacing it with a block-off plate, is that what you are recommending? What is left behind in the manifold when you remove the ACV?

About the MS1 - you are absolutely right, but I got this for free partially assembled so the price was right. I figure if I need to I can upgrade it to MS2, but it looks like I'll just squeak by with it. I've done the idle control valve mod on it already and I think I have enough outputs as really I just need 1 for the aux ports, 1 for VDI (if I can ever find a S5 intake!) and 1 for the electric fan, everything else is as per your guide.

Aaron Cake

iTrader: (1)

The RX-8 injectors are a good choice. That's why I decided to use them on my Cosmo instead of the more typical (and ancient) FC injectors. Remember they are high impedance and use a round Denso style connector.

You can remove the ACV and block it off. That will disable the emissions system by default and plug up most of the vacuum nipples on the LIM.

Zero10

You mention that it is important to note that RX8 injectors are high impedance. You said this because it means that I should set the current limit to 100% and crank up the time threshold in the configuration, correct? Is there any other meaning I should read into that? I will be removing the resistor pack for the stock injectors when I do the install.

Also, do you know where I can obtain decent quality wiring pigtails for the RX8 injectors? Are these the right ones? http://www.diyautotune.com/catalog/f...ev6-p-133.html

What is your take on deleting the EGR assembly? Unnecessary? I am under the impression if I simply do not power the valve it will remain closed all the time.

Aaron Cake

iTrader: (1)

Just set the MS1 up for high impedance as in the documentation. Then if you have low impedance secondaries you'll need resistors for them.

You need Denso style connectors for the RX-8 injectors, not EV6. I got mine here:
Sumitomo (Denso) - Female, Universal - Fuel Injector Connectors - Bosch Electrical Connectors & Denso Connector Adapters - SumitomoF/Universal, DENF

However when they arrived the crimps were terrible. I had to disassemble and re-crimp each connector. I sent an email to FiveO informing them of the quality and they said they would take care of it.

As for the EGR, just block it off. Mazda even removed it in newer models since the rotary has so much natural EGR.