Deranged Pineapple

I know it's been said a lot that the S-AFC is an old bad piggy back system and is a bandaid for more power, but my goal here is not to have super high power, just something that zips around pretty quick and can keep up with a B58. I have a 88 10ae with an already pre-installed s-afc 2, but it's unplugged (somehow came unplugged on the drive home after buying the car) and I have a fmic. As far as I know, it's a standard s4 t2 engine without any porting done or any hybrid turbos. Car used to make 12-13 psi on a straight pipe with RB y-pipe, but reeked of 91 anywhere in a 1/4mile radius of the car idling. I know very little about the s-afc 2 that I have and many instruction I see online are for the neo. My goal is to achieve good power when at like 3/4 throttle and up, but I'd also like to have somewhat decent highway gas mileage when I granny drive it (I still go through 1/8th of a tank every time I go to work and back maybe like 10miles almost all highway roundtrip). Is there a way I can tune for a leaner A/F when idle and going up to 3800 before the secondaries kick in and then after that tune for power? I might be asking for too much here out of the s-afc, but if I can do anything to help with the god-awful gas mileage (~80-100 miles per tank is ridiculous) while keeping power when I need it, it would be appreciated. Thanks!!

WondrousBread

That kind of mileage implies that you have aftermarket injectors that are larger than stock. That, or some sort of major issues causing a lot of unburnt fuel. On my NA I used to get ~450km to a tank, back when I measured it years ago.

As far as tuning, you basically need a wideband O2 sensor to do this safely. Doing it without one risks you leaning it too far and blowing the engine.

I would start with finding the SAFC II manual, and also a wideband & controller of your choosing. I'm using an AEM wideband and it works fine. Then once the wideband is installed, you'll have an idea of how rich it's running and how much fuel you can pull out.

Then, refer to this article. Much of it won't apply to you as it is focused on an aftermarket ECU, but Aaron gives some general advice about the target AFRs that you will find helpful. Remember that all things being equal, richer is safer. The more fuel you pull out at high load, the smaller your margin of safety.

WondrousBread

Also, I'm pretty sure the car you picked up was for sale here in Ontario not long ago. Where did it end up?

That intercooler setup looks a bit sketchy, so before you go tuning the car I would take a look and see if the previous owner did anything else unusual. Also, check that your MAF is sitting upright (black plastic cover on top). If not, the flapper door can be affected by it's own weight and throw off fueling.

Deranged Pineapple

yea, that's the one haha. From the documentation I have, the engine had a fresh rebuild in 2010-ish and was driven 42k km when I bought it, and now I daily it during the summer and fall months. I'll check for the MAF, but how would I know what size injectors I have? Would it be marked on it or would it have to be tested?

WondrousBread

For the primary injectors, there's no good way to tell from the outside. They are buried pretty far in there. Primary injectors are responsible for 100% of the fuelling below 3800rpm, so a rich idle (again, all things being equal) implies that they have been swapped out.

For the secondary injectors, you can see them a bit better. Your best bet is to try and get a flashlight and write down any numbers on the side of them. At the very least, take a picture and post it to see if anyone can identify them. If the primaries are swapped out, the secondaries are also almost certainly swapped out.

The stock ECU doesn't know or care what injectors are installed, it only cares about pulse-width. This is because as far as the OEM is concerned, injector size is a known quantity. Mazda tuned around the pulse-widths required for the stock injectors to provide the desired amount of fuel.

When larger aftermarket injectors are installed, these pulse widths provide a larger amount of fuel than intended. Hence the rich mixture. This is also probably why the SAFC is there. If I'm guessing, a previous owner added an FCD to defeat the stock fuel cut at 8psi. Then since the ECU is no longer cutting fuel and boost is higher, they wanted larger injectors to compensate for all the extra airflow. Tuning injectors isn't possible without an AFC, so they installed that too. Why they didn't at least get a wideband and actually tune the thing, I don't know.

This is all conjecture, but FCD + larger injectors + piggyback tuning was the popular way to go on these cars for a long time.

EDIT: Actually, I can see the FCD in the picture you posted in the other thread. Small black box by the MAP sensor on the passenger wheel well.

EDIT EDIT: I can also see the MAF is sideways

Deranged Pineapple

Thank you so much, I didn't even know where to start looking for the fcd. After a bit of research, it looks to be a KnightSports FBCD, but I'll have to confirm next time I go check on the car in storage. Ill pick up an AEM Wideband in spring time, but what I find strange is the presence of only a single O2 sensor bung on the downpipe being populated by the stock O2 sensor which confuses me as to how they tuned it originally? Also, another challenge I seem to face is the initial setup of the SAFC, as in what kind of sensor type. I'm assuming I set it to "flap" coinciding with what you said with the MAF. Who knows, maybe the settings saved from the last time this thing was run and it still has the old tune. On a quick side note though, I was planning on changing the plugs and was wondering if for my setup I was better off going all BUR9EQP all around? I looked at a few threads, but people hardly said the effects of running 9s on leading. Will this further improve gas mileage provided the same tune?

WondrousBread

If I'm guessing, they probably either didn't tune it at all or they tuned it by "feel". Which is acceptable IMO on an NA car, but unacceptable on a Turbo where the consequences can be much more severe.

With a wideband you will want to install a bung further down the pipe for it. You could use the stock location, but the EGTs might be higher than the sensor can handle and damage it.

"Flap" probably refers to a flapper door MAF, so I would assume that is the correct setting. I've never used an SAFC myself, so double-check to be sure.

If the SAFC has an input for throttle-position, keep in mind that the stock sensor is a narrow-range and only shows up to about 25% of throttle movement. So after 25% throttle opening, it reads 100%. You may need to tune around that limitation.

As far as the spark plugs, I also haven't tried anything other than stock. So you should do some additional research on that. I can tell you the following:

The higher the number on the plug, the "colder" it is. This is a bit counter-intuitive, but it means that a higher number plug is optimized for performance at a higher temperature. So when the car is just driving around normally, a lower number (like the stock 7 / 9 setup) is more efficient and sparks more reliably.

When in a high performance application, warmer plugs like the 7 / 9 can stay hot and cause a hot spot. This could lead to pre-ignition, which may cause engine damage. Again, just my layman's understanding.

So following this, the higher number only helps you if the intended use of the car is track only. It also provides a margin of safety for some street driven vehicles. However, it will probably lead to a decrease in efficiency and make them more prone to fouling under low-load conditions.

To make this more complicated, the leading plugs are fired in a wasted-spark arrangement. This means they aren't toggled individually by the ECU, both leading always fire together and one is "wasted".

So if my understanding is right, the benefit of colder plugs in the leading is probably little to nothing. It doesn't seem to matter if they are fired at an odd time.

The trailing plugs however are fired sequentially, so I think their position in the rotor housing makes preignition from the trailings more damaging and this is why Mazda ran 9s there.

If you look at how the rotor turns disassembled, this also makes sense. Since the trailing plug is exposed to the intake charge much earlier, pre-ignition there looks like it would force the engine backwards instead of forwards and cause a lot of stress. Meanwhile the later leading plugs are exposed to the charge when the rotor tip is a lot further down the chamber.

That is a combination of conjecture on my part and knowledge I've learned secondhand, so take it with a grain of salt and do your own research before deciding

DR_Knight

iTrader: (23)

Recommend using the boost pressure sensor as an input for the safc, especially since it’s s4 and you only read ~30% of the throttle range. You can search for my posts on it.

for your power goals, I’d recommend a bnr stage 3 hybrid turbo, at least an rtek ecu with bigger injectors at least 720cc, your safc, wideband, fuel pump, fmic, intake.

if you really want to do it right the first time, just build your fuel setup for e85, run a standalone ecu.

good luck.

Deranged Pineapple

Once I go back to straight pipe, Ill likely go back to boost pressure as input, but now to pass inspection I had a cat and resonator installed and now it makes 7psi on a cold day so it shouldn't change much. Until I get a new downpipe, I'll likely just lean out my 0-3800rpm to match with the upgraded injectors currently installed. My power goals are around the point of low 300hp, maybe upper 200s, so I feel like E85 (despite being impossible to find where I live) is overkill for that type of power as well as being a daily. I was looking into standalone for my car for a better longterm solution, but I can't seem to find anything plug and play like the old adaptronics (which I'd love to have), also I was looking into RTek ECUs as well but they're nowhere to be seen as well. BNR is a good idea, I don't want to grenade my engine with my stock s4 micro waste gate, but I feel as if I could probably get away with going s5 turbo with the dual waste gate setup.

DR_Knight

iTrader: (23)

Well if you are going to remove large amounts of fuel by running your oversized fuel injectors with a stock ecu map, you should probably read up on if a safc indirectly affects timing. I’ve always read that on multiple forums, and I’ve only made small adjustments with a safc so I never really thought any big timing adjustments were made.

so how much fuel will you need to trim out due to your larger fuel injectors?

https://maxima.org/forums/supercharg...dded-safc.html

WondrousBread

That timing thing makes me a bit nervous too. I don't know just how much fuel you can pull while remaining safe.

To clarify OP, have you confirmed that they are in fact upgraded injectors? That was just my hunch based on your description, so you should really confirm that before proceeding.

DR_Knight

iTrader: (23)

Yeah I became more interested years ago when I found out apexi also sold an ignition timing controller, the apexi S-ITC. I figured the SAFC and S-ITC were planned on being used together, and using both fixed any issues and allowed for the fuel and ignition control most would need before moving to a full standalone.

Can simply retarding timing account for the timing adjustment at WOT full load? Possibly. I forget how many degrees rotating the CAS changes (too lazy to look it up, but the OP should).

Deranged Pineapple

I checked up on my car in storage today quickly in my spare time and attempted to look for the modifications that were done, but unfortunately I didn't have my tools on me. I tried squeezing my phone camera to take a picture of the secondaries, but in the dark parking garage all I got was a blurry mess of a photo and it was too blurry or grainy to make out any lettering, when I take it out of storage mid march, I'll give it a second attempt. I did some more research and read that it was also popular to chip swap the OEM ecu to an RE-Amemiya or Rtek chip for example in order to compensate for larger injectors (I think it corrects for timing too?) so I'll also pull off the ECU plate next time I see the car and look for that REDOM or RTek sticker.

Something I WAS able to confirm, or I guess not, was the FCD. I flipped the box, It didn't say knight sports or anything of the sorts, it was just a blank black box with no branding or stickers, so it's likely a racing beat FCD since those seem to be unbranded as well.

Let's say I get the fuel thing figured out with the SAFC, without scratching my head over what to do with timing and stuff, the next logical step is the standalone. It's definitely an option I'm considering for this summer after the car is painted. Question now remains: What's something that's the MOST POSSIBLE plug and play to use my existing harness? I was looking into the Adaptronic eMod009 made for FC which seems completely plug and play and easily swappable (if I can even find one to buy somewhere), or even the PowerFC which requires a new set of trailing coils and the banzai harness. Is there another option I'm missing?

(I did take a look at haltech, but going through an entire harness swap as well as still doing some wire-work, I just want to save my self the headache in case I ever want to sell the car as stock as possible. Also, my current engine harness isn't a deep-fried crispy mess like most FC harnesses, so it's not hopeless)