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Old 04-26-2004, 10:05 AM   #1
powerlabs
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Cool Tuning S-AFC with blue wire mod.

So I finally got around to doing the blue wire mod on the Apexi S-AFC I have installed on my 1999 Impreza 2.5R.S. For those that are not familiar with it, the blue wire mod consists in tapping the first oxygen sensor signal from your ECU and reading its voltage from the S-AFC.
The first thing I noticed is that when the engine is under partial throttle it reads ZERO volts.
When the engine is idling the signal climbs to .5V, then back down to 0V, cycling once every couple seconds.
At WOT I had to add 9% more fuel at 3000RPM, going up to 22% more fuel (! ) to get a consistent .84V reading to redline.
22% seems like a LOT... Can anyone comment on this?
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Old 04-26-2004, 03:00 PM   #2
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If you have an intake or exhaust upgrade, it sounds normal. Well, maybe on the high side of what it should be.

We run that much correction for our max power settings. We also ran no cat (until very recently) and very open exhaust along with a true cold air intake routed to a bumper vent.

Kinda goes against the status quo of leaning out Subaru's supposedly rich factory settings, eh? Trust what you're reading on the meter....We learned the hard way by leaning to the point of misfires and major bogging during the 2002 Solo II Nationals. Once we were shown where we went wrong by truly skilled tuners, we went from -15% to +30% and disconnected the FPR for max pressure at all times. The result was 4 wheel burnouts during launching and a car that was another pace ahead of it's drivers, resulting in cone carnage. It made a believer outta me...

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Old 04-26-2004, 03:30 PM   #3
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How exactly do you tune one of these things? I will probably be getting one soon (SAFCII) and would like a bit more information. Is it something a noob, such as myself, could figure out? Or is it something I should take and have done by the pro's? How about installation, it is just plug and play isn't it? I was told by my tech that my car was running too lean due to my intake/exhaust and that that was why I burned out my O2 sensor. Any help would be appreciated.

BTW, about this blue wire mod, is it that much more helpful to tune?
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Old 04-26-2004, 04:18 PM   #4
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Storm:
Thank you, that is what I was hoping to hear! I also suspected the reading was correct because with the new J-tube intake the engine ran so incredibly lean that the ECU actually forced a fuel cut at 5500RPM! With the S-AFC I was able to increase fuel and get the fuel cut to go away; in fact, the engine can now rev past the stock red line, all the way to about 65000RPM or so
I still wanted to check though because 22% just seemed excessive. I'm worried that this will kill my fuel mileage.
BTW my car will also peel all 4 of its Kuhmo Ecsta MX tires on a hard launch... That's with Borla Headers and catback, UD pulley J tube intake and Exedy clutch. I decided to substitute the intake for an Injen CAI and add a Random Tech high flow cat and Magnaflow resonator to the exhaust, so with that, and my new cams later this summer it should really come alive
SjYankee006:
I installed it myself; it requires stripping some wires on your ECU and connecting them to the S-AFC wiring harness; I recommend soldering everything. If you can strip and solder wires, you can do it. Mounting it was a breeze too, but I cheated a bit and used a gauge pod to mount it ;-) Looks awesome; everyone who rides in my car compliments it Now its extra cool because I put the Subaru Carbon Fiber trim to go along with the Carbon Fiber mounting plate that holds the S-AFC to the gauge pod... Photos of that comming soon.

As far as tuning it; I found an empty road, put it in 2nd gear and floored it, monitoring the voltage reading from the oxygen sensor as the car sped up and the RPMs climbed. At first the voltage was very low, so I started adding fuel on the setting curve. I just kept adding fuel untill the reading was around .800V - .840V throughout the entire RPM range. The entire process took maybe 6 runs. It is not possible to tune the S-AFC without some sort of air fuel gauge or reading from the oxygen sensor. In a way, the blue wire mod is the quick n' cheap way of tuning it. Ideally you'd want to get it tuned on a dyno (my plans after I get new cams), but for a rough adjustment the blue wire does the trick. An A/F gauge would be a little better than the blue wire mod, as it would give you an actual air/fuel ratio reading, but AFIK those also run off the oxygen sensor in the exhaust, so the accuracy would be about the same...
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Old 04-26-2004, 04:27 PM   #5
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Very cool, thanks a lot for all the info. I thought the SAFC gave the air/fuel ratio as well, but I guess it wouldn't without the blue wire O2 readings.

So how's the car running now? Did you feel any gains now that the car is getting the fuel it needs?
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Old 04-26-2004, 06:53 PM   #6
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Ummm... I haven't noticed much to be honest with you. Power delivery seems smoother, but I find it hard to sit down on the car, nail the gas, and say "it feels like it gained about 10 horsepower". Honestly I think people that think they can do that are fooling themselves, like the guy who posted a review for a Perrin Radiator Shroud saying it feels like his car gained 15 horsepower from it (oh, and don't even get me started on horsepower producing spark plug wires and grounding kits!).
Having said that, the difference between 0% correction and 19% correction (what I was running before, thanks to some advice I got on the board from another member with an S-AFC) was quite dramatic; the car went from bogging down at 5500RPM and cutting out to accelerating hard through the entire rev range. From 19% to the 22% I'm at now though the difference so far seems negligible...
We'll see how it goes with the Injen CAI and the Random Tech Cat though... Maybe those will produce enough power for me to hazard one of those "butt dyno estimates" that I dislike so much...
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Old 04-27-2004, 02:03 PM   #7
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Got a more recent picture of my Apexi S-AFC installation with the S-AFC showing the correction curve I am using right now:



I still want a dead pedal (Sparco doesn't make one; maybe an STI or a WRX will have to do? and more carbon fiber trim (gauge bezel, door handles, vent covers?)
But I think it looks good for now. Comments?
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Old 04-27-2004, 04:22 PM   #8
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Looks pretty good I'd say. Whats with the RS mats turning that funny green color, mine look like that too. The carbon fiber trim stuff is a bit much for my taste. I like the pedals though. How do they feel? I've been looking at those, and the Sparco Grip Pedals.
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Old 04-27-2004, 06:25 PM   #9
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Powerlabs- I've tuned via blue wire as well and I too ended up having to richen my top end up pretty considerably. I have a 98 though and I think that the 98's dont suffer the same issues with incorrect maf readings when using intakes that the 99's do. I tried using the reccomendations for the 99's, like richening up the top around 25-26% after 5k and my motor just bogged from being too rich. Right now I think I'm at about 15% +/-.

I like your mounting location, I really need to mount mine and I think I will try to pursue something similar.

Post as soon as you put your Random tech cat on, I want to hear the differences. Oh yeah if you can, install just the cat section and then do some testing, so the different intake (Injen) wont confound anything. I'm either going to buy a Random Tech as well or sell my Borlas and by MRT's or a Cobb header and cat section.
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Old 04-28-2004, 03:03 AM   #10
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Interesting. I dyno tuned my S-AFC and had to lean the car out throughout the RPM band (full exhaust, Cobb heads and cams, CAI) to get the AFR where it should be. The dyno had a wide-band O2 sensor, so I was relying on that to tune.

With that said, over time the car has developed some often severe mid-range hesitation as it pulls timing (verified with a PocketLogger OBD2 scanner). I've tried richening the mixture and it never seemed to fix the problem. I've been thinking of doing a DIY wide-band O2, since I need to do one for my other car, but I haven't gotten around to that yet and this would certainly be cheaper.

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Old 04-28-2004, 04:00 PM   #11
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Nunyo:
Quote:
Whats with the RS mats turning that funny green color, mine look like that too. The carbon fiber trim stuff is a bit much for my taste. I like the pedals though. How do they feel? I've been looking at those, and the Sparco Grip Pedals
Well, those mats haven't been properly cleaned since the beginning of winter; they were frozen in place for all of winter and then mudded over in spring, so now they probably have their weight in mud/salt/rocks... I remember they had a nice perfectly clean stripe on them for a while after I used them under whe wheel to try and get my car moving once it bottomed out in snow on a snowmobile trail
Oh, I found a Sparco dead pedal!!! I ordered it and when I mount it I'll clean the mats properly and take a picture of it. About the pedals; they feel great! The stock ones looked ugly, were small and slipped when my shoes were wet. These feel nice and solid even with ice on my shoes. My next buy should be some Sparco racing shoes

Compressed:
Quote:
Post as soon as you put your Random tech cat on, I want to hear the differences. Oh yeah if you can, install just the cat section and then do some testing, so the different intake (Injen) wont confound anything. I'm either going to buy a Random Tech as well or sell my Borlas and by MRT's or a Cobb header and cat section.
I'm installing the Injen CAI tomorrow. I'll tune it, do some runs, and Friday when I install the Random Tech Cat I'll check if it affected the tune at all and give my "butt-dyno" opinion on it. I ordered a stainless steel Magnaflow resonator along with my Random Tech Cat. My ideal would be to make the car *quieter* with the high flow cat and CAI then it is now with the J tube intake and the header/catback combo. No idea if it'll work or not, but I sure hope so... Small town cops keep giving me the looks. Damn some times I just wish I could flip them off and race on, but they know where I live...

Pat: In my understanding, timing advance and retard is controlled by the ECU on a per-knock basis. That being the case, maybe you could solve the problem by de-sensitizing the knock sensor (placing a small piece of rubber between it and the engine block)? What do you think of that? Have you tried high octane gas/octane boosters? That would at least give you a confirmation of whether was was knock going on or not...
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Old 05-02-2004, 09:46 PM   #12
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OK, so yesterday was the first part of my car summer tune ups/upgrades...
1- Installed SPARCO dead pedal (matches my pedal set).
2- Installed HELLA dual tone horns behind front grill (YES, I like to hit the horn at stupid people who get in my way! And the stock horn just wasn't intimidating enough ).
3- Installed Primitive Racing Radiator Shroud (radiator foam was GONE)
4- Installed INJEN CAI.
What we are all interested in of course is the CAI:
1- Did the full install (new thread coming up on this forum shortly), reset the ECU and reset the Apexi S-AFC.
Now the oxygen sensor reads 790 - 850 throughout the RPM band; in other words; the Injen intake is well designed enough that the car will run VERY well with it with no real need for any correction! Of course, I can still fine tune with the AFC (working on that), but it will be a FAR less dramatic correction curve.
2- MUCH quieter intake... The J tube I had at WOT was louder than my radio and exhaust together. The Injen makes my car sound like a superbike, but a quiet one. I like it!
3- No discernible difference in power level so far.

Next week: Random Tech High Flow CAT, Magnaflow Resonator, STI Transmission mount.
Next month? COBB cams
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Old 05-02-2004, 11:16 PM   #13
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whered you get the pod for the afc
cause im interested in gettin an afc and if i could get that pod for my legacy L 98, itd b tight
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Old 05-03-2004, 03:39 AM   #14
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Quote:
Originally posted by powerlabs
Pat: In my understanding, timing advance and retard is controlled by the ECU on a per-knock basis. That being the case, maybe you could solve the problem by de-sensitizing the knock sensor (placing a small piece of rubber between it and the engine block)? What do you think of that? Have you tried high octane gas/octane boosters? That would at least give you a confirmation of whether was was knock going on or not...
I've run high octane gas ever since I had the Cobb stuff done. Heads and cams shouldn't have had any effect on static CR, but there may be some increased dynamic CR (or maybe I'm just talking out my ass ), so I figured it was a safe move. I've tried lower octane gas with no discernible change.

I've tried "fixing" the situation by removing the knock sensor from the block completely (but leaving it plugged in, so the ECU didn't go into some sort of limp mode). I zip-tied the sensor up away from the block. Again, no discernible change.

Pat
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Old 05-03-2004, 12:09 PM   #15
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Weird... I can't see any other reason why the ECU would pull timing advance other than the knock sensor... I guess I just don't know enough about how it works
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Old 05-03-2004, 05:56 PM   #16
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Default Sparco pedals

Aha, got my dead pedal:

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Old 05-29-2004, 11:14 AM   #17
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Greets all,

First off, awesome thread!!!

I too have picked up a S-AFC II and plan on installing it over the next week or two. Someone had asked about the Pod for mounting, I picked up mine from Jamie. See:
http://secure.cartsvr.net/catalogs/c...showprevnext=1

I've also picked up a PLX M-300 Wideband O2 kit in order to tune it. For this see:
http://www.plxdevices.com/M-Series_productinfo.htm

Now, one of the "options" of the M-300 is to replace the existing 02 sensor with their wideband. They have a 0-1V analog output that you can feed to the ECU.

My question is, in order to replace the stock O2, it has to meet this voltage curve:
http://www.plxdevices.com/PLXApp004.htm

Before I re-invent the wheel and try to map the output voltage for myself, has anyone already done this? Following this thread it looks like I might be OK but folks seem to be shooting for .8V rather than .5V so I figured I better check.

Any and all input greatly appreciated,
Chris
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Old 06-02-2004, 04:08 PM   #18
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Sorry I can't help you with the O2 sensor conversion, but as far as the 0.840 V tuning; I too wonder why that is the preferred setting; with both my intakes getting to that involved richening up the A/F ratio curve quite a bit. Let me know if you find out where that number comes from
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Old 06-02-2004, 04:28 PM   #19
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I've done some poking around on the Web and it appears that all Bosh narrow band O2 sensors are pretty much the same, kicking out .5V at a 14.7 ratio. With this in mind, I think I should be able to do the swap, no problem.

Just curious, where did you get .84V as the preferred setting?

I'll let you know how I make out as it looks like we have a similar setup:
MY01
Injen CAI
Borla headers & CAT back
Random Tech CAT

CheeRS,
Chris
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Old 06-02-2004, 05:54 PM   #20
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The .84V is floating around all over the NASIOC board... I read about it here
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Old 06-03-2004, 01:24 AM   #21
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not to hi-jack, but why cant i find info. anywhere about putting an s-afc in my 02? damn!
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Old 06-03-2004, 12:44 PM   #22
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It should be the same as installing it on any other model year...
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Old 06-03-2004, 06:05 PM   #23
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nope
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Old 06-04-2004, 10:45 AM   #24
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Quote:
Originally posted by darioc
nope
From what I can tell, based on other threads posted several months ago, the ECU in 02+ 2.5 RSes learns around any corrections made by a S-AFC II or other comparable air/fuel controller.

Sucks to be us
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Old 06-04-2004, 03:09 PM   #25
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Quote:
Originally posted by DrBoy01
From what I can tell, based on other threads posted several months ago, the ECU in 02+ 2.5 RSes learns around any corrections made by a S-AFC II or other comparable air/fuel controller.

Sucks to be us
00-curent 2.5RS. Or pretty much the MAP based one's. But the good news is that it hasnít been proven yet, still giving us hope. But it probably wonít.
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