I am having a problem with my S-afc II. I have an S4 with a s5 to4 hybrid, ported Wg, custom 3" intake, 2.5 dp/mp, N1 catback. 720 seconds, Walbro 255, (rewired)
Before I had the S-afc tuned to my stock turbo with no problem. But, now the only thing I did was change out the stock turbo for the one listed above. I hae 10 dyno runs with the correction going from 0% to 30%, and nothing changes. The lines are exactly the same on all 10 runs. (overlapping)

I checked the install and all is good. I called Apexi and they said that all sounds to be working right, might be somthing else. The car is running lean right now and I cant get any more fuel no matter what.

On the street if I load up the "low" with up to 15% the car boggs and hesitates. (running way rich) So its working but its not? Can anyone help? Could it be the pump not flowing enough? Fried ECU? Fried S-afc? (all works on the safc though) Thanx!

 

you are probably maxing your injectors out. if you are trying to add more % and it's not changing...

you should be at -% with the S-afc. if you need to go +% then your injectors are too small.

how much boost are you trying to run???

maybe time for four 720cc's

 

I have the stock 550cc in the primary's and the 720's in the secondaries? Running 10psi. Dyno at 281- 295 wrhp, running pretty lean. You think the injectors are maxed? I woundt think they are. The lines dont move at all.

 

that is getting to the limit of those injectors tho. i got my stock set back from RC engineering and they don't recommend running more than 250hp on stock injectors.

here is what the sheet says exactly
@BSFC of .65: 256.7
@BSFC of .55: 303.4
@BSFC of .50: 333.7
that is with 2190cc/min flow rate at 80% duty and 43psi fuel pressure.

 

as I said your S-afc should never really be in the pos % range. maybe max +5% should be neg. get some bigger injectors.

 

285-290 rwhp with just 720 secondaries and 550 primaries? Like it's been said you've maxed out your injectors.

 

Maxed out the secondaries or the primaries? Or both. I wouldnt think the 720's are maxed out, but do you guys think I need bigger there too?

 

720's aren't that much larger than 550's. by maxed out, we mean all your fuel injectors as a whole can't flow anymore. the 720's certainly helped, but they are no longer enough. if you don't plan on doing any more mods, try a set of 850's. they may be able to bring you back to a safer level. otherwise, you're looking at replacing your primaries with 2 more 720's.

doing the math here...if 4x550 = 2200 = 250hp
then 2x550 + 2x720 = 2540 = 288hp and that's right where you're at. your injectors can't put anymore fuel in the motor but you can lessen the amount of air. put your stock intake back on. you shouldn't run lean anymore. haha

 

all 4 are running over 3800rpm so you maxed out the total.

you could increase either. but I would increase the primarys to avoid running lean before 3800 rpm.

four 720cc's should work nicly.

 

oh, 2x550 + 2x850 = 2800 = 318hp
4x720 = 2880 = 327 hp

 

ahh, never even thought about that. ya, i'd do that. plus you get a higher limit in the end, vs running the 850 sec.

 

i was wondering tho. did you have any noticeable drivability problems when you first put in the 720's? i'm considering getting some.

 

So 4X720 should do it. Then lean it out with the s-afc? Thanx for all the help!

I had no issues when I added the 720's with the stock turbo at 10psi. The hicup everyone talks about wasn't even noticeable. I did have to lean out the mixture though but it ran really well.

 

Or should I go bigger, They seem to cost the same. Would 2x720 + 2 1600's be to much, or could the safc handle it?

 

1600cc is way more then the S-AFC can handle, time to go standalone perhaps.... but as said above, you will probably be fine with 4X720cc and another run at the dyno, otherwise you can allways try shis setup first, and then sell the 720cc´s if you wanna upgrade further in the future, you won´t loose that much money anyway plus it is fun to upgrade in steps, right?

 

Guys I have 680's and 720's (turned out Enzo250 sold me 680 but had said they were 720cc and posted them for sale as 720's) But I added 720 and moved the 680's, And I still cant move my fuel curve. It runs really rich on the street and boggs from so much fuel. My a/f ratio moved 1 point and I can't lean it out or richen it. I even turned down the boost and no change. Last run a turned it way down to 9psi it it went from 12 to 15 on the a/fwith black smoke out the tailpipe. Something is wrong. The a/f ratios should move if i turn the boost down from 12 to 9 right? Or if i take away 10%. Nothing. Dunno what to do. Cant imagine I need more fuel. Any help woould be great! Thanx! From the looks of it if I need more fuel I would need a lot, I added 300cc (12%) and it barley moved, Not even a whole point. I would need like 1000cc injectors. But even with the boost lower and less power like 257rwhp at 7psi same curve on the o2 sensor. ??

 

What injectors are you running and what boost? Did u tune it?

 

I have not dynoed yet. Everything is isntalled in the car, but now its winter here in Sweden and we have alot of snow.... so the car sleeps!

I think your problem is related to the S-AFC and not the injectors. As you say, you are runnig rich now and it would really be enough fuel for now.

What did you set the Hi and Lo settings to? They are very important, i used to run it with Lo=0 and Hi-99 and nothing happened, then i started to read and try things out, and now i run Lo=20 and Hi-45 and it made a huge difference - that was with stock injectors and boost turned down, just before the snow.

 

i Adjusted mine per 1300cc.com. 97-99 I think. I read a lot on the forum to and a lot of people run high numbers like that because of the tps. So I can have a bit more range with the low set at 97. Doesnt really do to much, usually its on high.

 

To set the Hi-setting over 98% is probably a good thing for the S4 because of the TPS being limited, but i have a S5 with "full-range" TPS so i dont have that problem - hence i can have it on 45%. Sorry i forgot you had an S5.