Looking at a fuel controller to use with my Series 4 RX7 non-turbo. The plans for the engine currently are to make it as efficient and make as I can on the stock engine. The plan is the following:

- 4 - RX8 Secondary Injectors
- Fuel Controller (Recommendations Please)
- Corksport Headers
- Corksport Catback
- Retain Main Cat Only
- Parallel fuel Mod (should this be necessary for reliability?)
- Aftermarket Fuel Pressure Regulator (Recommendations, I don't need anything exotic)
- Aftermarket Fuel Pump (Recommendations?)

Now I've done my research on the RX8 injectors, the miata guys have been using FC RX7 injectors and a few have been upgrading to RX8 yellow injectors which are also plug in play mechanically and electrically same as the FC injectors, RX8 injectors although some sources say 380cc are actually around 450cc, which should be plenty for an modern injector in the NA 13B engine.

One controller that I was recommended to get was the AEM FIC, which seems really nice. Does anyone have different recommendation?

The Parallel Fuel Mod seems like a good idea while I'm at it, but I don't really understand the benefits of this mod. Could someone explain this? All I'm seeing really is for higher horsepower.

I'm also considering getting a fuel pressure regulator and fuel to replace the stock one, I'm thinking that I will need to be able to have higher fuel pressure with the new RX8 fuel injectors. Does anyone have the RX7 S4 fuel pressure. I need this bit of info because I'm sure the RX8 runs at a different fuel pressure rates.

Mind you, this is all on a NA setup, looking at modifying, improving power, stability and reliability. Sorry if I seem to be all over the place, just trying to cover all my bases as far as the fuel system is concerned. Thanks for any help.

 

Aren't the stock S4 NA injectors already 460cc?

And what's the "parallel fuel mod"? Isn't that where you run one grade in the primary rail and a whole separate system and higher octane fuel in the secondary rail?

If that's what you're referring to, then you're wasting your time. That's not going to get you any power from an NA, and is DEFINITELY not necessary for an NA. Nor is it more reliable. More parts = more stuff to break. If it's larger injectors that you may EVENTUALLY need, then GSL-SE injectors are 680cc. TII's are 550cc.

Right out of the FAQ:
Year Engine Plug Size Colour Part #
84-85 13B NA, low square center, 680cc, orange, 195500-0900
86-87 13B NA, low square center, 460cc, red, 195500-1350
86-87 13B Turbo, low square center, 550cc, tan, 195500-1370
88 13B NA, high square offset, 460cc, purple, 195500-1350
88 13B Turbo, high square offset, 550cc, purple, 195500-1370
89-91 13B NA, high oval center, 460cc, red, 195500-2010
89-91 13B Turbo, high oval center, 550cc, purple, 195500-2020

 

I'd just grab a RTEK 2.1 for an N/a..use some clean injectors and If you want to,make up a parallel fuel setup that you can use Later on a TII based engine(because you will Want to,after you do all this!).
The only thing that you would really be looking at is to get rid of the PD(pulsation dampener) as is not reliable(causes fires if it goes).you can do that if you build the parallel sytem with A/N fittings..NOT cheap though..(about 400 bucks all together.)
The Fuel pressure regulator would be kind of useless,BUT overall With a FD Pump in the tank,that would be OK.(either an FD pump or a Walbro 255)
The above parts would be great to use if you went to a TII swap later on.

 

Agreed, use the RTEK.
Dis-agree on the parellel fuel system, its just a lot of extra crap to go wrong.
Agree on getting rid of the FPD, its just not needed.

 

Yes, I'm quite aware of the stock injector size, which is 460cc. The RX8 injectors are however from what I read are around 450cc at 43.5 psi. Now the theory behind running the RX8 injectors, which are far newer and use much newer technology then the old stock injectors, is that the newer injectors from the RX8 atomize fuel far better than the older ones. Now from the way I see it, the better the fuel is atomized the more complete burn you have, which means technically you can use less fuel for each spray burst from a given injector, which translates into better mileage, more power and also the other given benefit is better idling and smoother acceleration. In my opinion this is all necessary to make an engine more reliable then it was from factory, have more power, and just over all more efficient. And honestly, I'm very curious as to what results I will get from these modifications.

 

Yeah I think your right about the Rtek 2.0 (2.1 isn't available for NA). I almost completely forgot about it. Thanks for the reminder.

So the parallel fuel mod is basically a waste of money, ok, I can go with that. Seems that the best idea would be to change out the old lines from the firewall to the fuel rails.

Now what about the FPR? will I need to change that out to something that works for higher fuel pressure, assuming that the newer injectors require higher fuel pressure than the stock system can provide?

 

Well, the FPR, thats something for you to play with. However, do not buy into all the hype surrounding "new" technology for injectors. The nice thing about RX8 injectors is that they are new, but again I would not get too worked up over them, as I highly recommend ANY used injectors be cleaned/tested before you put them in your engine, even if I heard them run a car before buying them. If it were me, I would just call FIC and get a nice fresh set at a reasonable price. Or I can call for you, I love those guys

 

Is this a stock-port s4? If so, that's a lot of work and expense to gain next to nothing in power improvements. An injector is an injector, in theory new aftermarket injectors will have the same 'advancements' as new oem ones. Now if you were trying to go direct injection, that would have some impressive gains.

Running the fuel rails parallel is a waste of time on a stock n/a...

 

Eh, I'm just going to experiment with the idea, RX8 injectors aren't horribly expensive and the basically plug and play from what I'm hearing from the Miata guys who have used both RX7 460cc injectors and the RX8 Yellow injectors. If there is any benefit to it or not, I'll post the results.

 

Be interesting to see a difference. I think you're over accomplishing ideas for an n/a, but hey that's not a bad thing

 

If you want maximum efficiency with newer fuel injectors, then you will need a fuel controller that has very high fuel map resolution, dead time compensation and/or some type of individual injector trim, and tunable sequential fuel injection. A simple piggyback is not going to make your Clark Kent 1980's ECU into Superman. I think you are going to need a full-featured EMS rather than a piggyback band-aid.

Probably not necessary, but you can modify the stock fuel rails into a parallel system for a minimal amount of time and money:
http://fc3spro.com/TECH/MODS/FUEL/pararail.jpg

Use an Aeromotive or SX brand regulator that has a built-in pulsation damper function. An EFI regulator with -6 size feeds will work fine, and you probably want the rail pressure somewhere in the 40-45psi range.

Bosch is made better than Walbro.

Witch Hunter tested them at 425cc@3bar.

The AEM FIC is made to work well with OBD-II and CAN-BUS systems. Unfortunately, your car has neither, and even if it did is still has the low-resolution stock ECU ultimately running the engine with a piggyback attached. I recommend a Motec M400, or whichever full-function SFI EMS that your local tuner uses.

The acceptable stock fuel rail pressure range is 34.1 to 39.8 psi as per the factory service manual, which averages out to 36.95 psi. I assume this relates to 2.5bar (35.26psi).

 

Thanks for the information so far, very helpful.

 

hey i make fuel rails, and i have 4 rx8 injectors...the rx8 injectors, atomize fuel much better than the s4 injectors...i also have some id1000 injectors....i also carry TONS of AN fittings and fuel hose in stock along with some used fpr's

 

You do NOT need an upgraded fuel pump for an N/A. A fuel pump re-wire might be worth you time if your current setup is seeing low voltage. I'd check your tank too while you're at it, a rusty/cruddy tank can will **** up the best planned fuel system...

 

Yes, thats right, a simple OEM replacement pump is fine for N/A's, but you can use an FD pump for an upgrade if you so desire.

Agree with EA about the EMS issue, but will add that the FIC will work on the S-4 if you really wish to use it, as will the MAP-ECU 1 or 2. Either will give you reasonable control over the fueling, whether you can use the injectors to optimum or not I have no idea, I try and stay far away from piggybacks.

As far as injector testing, the same injector can and will test differently because of manufacturing tolerances, how much use/wear it has, voltage, even the type of "fuel" used in the test. As I said earlier, have the injectors tested and if need be cleaned before use unless you have bought them new from someone like FIC who tests thier injectors. Even new injectors from Mazda wouldbe suspect, as the ECU's learn which injectors flow differently from each other and adjust flow, which your ecu does not.

 

Fair enough, I think the best bet for the time being is to use the Rtek 2.0 modification then, will likely be easier to work with.

Injector testing is already being planned, to whom I send them too is a good question. There's RC Engineering, Witch Hunter Performance, Fuel Injector Clinic, at the moment I'm not all that sure who to send them too, is there a difference between them other than price?

I kinda figured that was the case, these ECUs are some of the first iterations of EFI that came out, I didn't think they had that capability anyways.

 

I am trying to get as much out of my NA as possible also. Going to be going with t2 550cc injectors for secondaries and an Apexi-SAFC II. Can't really say any good or bad but just thought that I'd chime in and let u kno what I will be using.

 

Interesting, okay, let me know what happens, also why not just get the Rtek 2.0?

Anyways from what I know, you will certainly get more fuel flow, but atomization should be the same. I'm moving up to RX8 injectors which supposedly flow 450cc according to someone that sent there's in. According to the forums they are rated at 380cc, some other places say 420cc. But who knows until I test, I figure I'll probably get around the 450cc range myself. Either way one guy running the RX8 injectors on his miata, upgrading from the RX7 NA 460cc injectors, noted that he was running richer all over the place after he installed them, which to be honest is rather interesting. I expect similar results.

 

I think a piggyback is a waste of time and money for your stated goals. If money is a factor (which it always is, lol) then you could just upgrade the fuel system and set the aftermarket fuel pressure regulator in order to make the new injectors mimic the output of the stock injectors. You could then run your car with the stock ECU until you have the money for an EMS, installation and tuning. You can use the "Fuel Flow After Pressure Change Worksheet" at this link to figure out the required fuel pressure:
http://www.rceng.com/technical.aspx

In a typical parallel system, the fuel pressure regulator is the T, as this reduces plumbing and restrictions, and helps balance the two fuel rails. If the regulator is used on a stock-type in-line fuel system, then only one inlet/outlet would be used and the other would be plugged.

Features you want:
- Rated for fuel injection
- Works in the 40-45psi range
- Has two inlet/outlet ports sized at -6 AN (ORB-6) or 3/8" NPT

These high-quality regulators have the above features:
- Aeromotive 13129
- Aeromotive 13109
- SX 15404 (Some models have a gauge port, others do not)

Those are just brands. If you get a replacement pump, choose one with an output similar to the stock pump. If the output is too high then a lot of fuel will be bypassed, heating the fuel and reducing engine output. PWM fuel pump controllers are available to run high-output fuel pumps during lower-output conditions, but I would imagine that you would want to try to avoid this due to the cost.
http://www.jegs.com/i/Aeromotive/027/16306/10002/-1

As mentioned earlier in the thread, you may want to clean out your fuel tank. Also, it's not such a bad idea to replace your fuel filters and check to make sure your fuel lines are not cracked or corroded.

That's why you should get a nice fuel pressure regulator and standalone EMS for maximum efficiency.

 

you are forgetting turbosmart!!! aeromotive and sx are garbage compared to turbosmart btw this quy pays super quick for injectors!! bump for a good buyer!

 

Ok, now this makes a lot of since, later on I'll have to figure out what EMS to use. Now the question I have is can the stock NA fuel pump provide the needed fuel pressure to work with the new injectors, like you said earlier, the fuel pressure averages around 36.95 psi. Would that fuel pressure rating be from the fuel pump or after the stock fuel pressure regulator? If it's after the FPR then that FPR needs to go and a replacement fitting needs to go there so I can hook up a proper FPR like stated. If it's from the pump then the pump needs a replacement too.

Ok, now that makes a lot more since, but if I recall correctly, that would mean that there was 2 FPRs in that picture, including the T. Correct me if I'm wrong. I'll check out those FPRs sometime.

If I replace the fuel pump, I'd think about getting an FD pump, that should be enough for my needs, however that may not be the case, and I may just need a replacement pump.

Also planning on taking care of this, basically part of a good tune up.

Eventually the EMS, for now I think I'll work with a nice FPR to regulate things with the Stock ECU. Although I'd love to get my hands on a decent EMS.

 

hehe i have a haltech e6k for sale and a platinum 1000 haltech

 

If only I could afford it now, for now it's one step at a time. Too bad I don't have a full blown shop at my disposal as well as some helping hands.

 

Which Turbosmart FPR has an aerospace-grade fluorosilicone diaphragm that acts as an accumulator and pulsation damper?

The stock fuel pump should be fine if it is in good shape. If it turns out that it can't support your fuel requirements then you can replace it. Just watch your fuel pressure and AFR to make sure it is supplying enough fuel.

The fuel pressure you want to watch is measured at the fuel rails (or at the FPR), as this will be your fuel injection pressure. The fuel pump will operate at a much higher pressure. See the factory service manual for the standard specs.

The stock FPR can't be adjusted like the nice aftermarket units..

No, it's just one FPR with two inlets, one from each fuel rail. The fuel outlet goes out the bottom of the FPR and back to the fuel tank.

 

Ok, I've finally found the fuel pressure ratings for the NA 13B.

FPR - 35.6 - 37.0 psi
Fuel Pump Outlet Pressure - 64.0 - 85.3 psi
Fuel Pump Feeding Capacity - 0.35 gpm (gallons per minute)

So by these numbers I have some interesting numbers that I'd like to verify. According to an online calculator and sources.

Stock NA FC Injector - 460cc @ 43.5psi

However since the regulator lowers the fuel pressure, it seems that our injectors are using this rate:

Stock NA FC Injector - 416.13cc - 424.24cc @ 35.6 - 37psi

Now by my thinking, the same would hold true for the RX8 injectors. But at the moment, I don't have the specific output of the RX8 injectors that I'm getting, but if we go by 2 sources,

Stock Secondary RX8 Injectors - 425cc @ 43.5 (Witch Hunter Performance)
Stock Secondary RX8 Injectors - 450cc @ 43.5 (Findings from someone else)

Stock Secondary RX8 Injectors - 384cc - 391cc @ 35.6 - 37psi (Witch Hunter Performance)
Stock Secondary RX8 Injectors - 407cc - 415cc @ 35.6 - 37psi (Findings from someone else)

Now the RX8 injector numbers are the probable numbers and indicate that a change in FPR is needed, but do to much better atomization of fuel by newer injectors that may not be the case, so the only way I will be able to tell is when I get a decent Wideband setup.