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Discussion Starter · #1 ·
I had my car tuned with an S-AFC 2 on 93 octane before i went full BPU. A/F ratios did not exeed high 11s. Since then I've added an exhaust (which makes the car richer), but have moved to a place where 91 octane is as high as it goes. I was told i should perhaps bump down the S-AFC 2 corrections.

1. Is that true?
2. Will the exhaust offset the change in gas octane?
3. How do i do it? The S-AFC is complicated.

THANKS
 

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if you have a wideband, just retune it..i just got mine yesterday n its incredibly simple if you just sit down n mess around with it...DONT fuck with it tho if u dont have a wideband obviously ull risk leaning it out, just go through the HI throttle and add/take out fuel where needed until the A/F's are mid-high 11's again.
 

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Discussion Starter · #3 ·
sngledsupe said:
if you have a wideband, just retune it..i just got mine yesterday n its incredibly simple if you just sit down n mess around with it...DONT fuck with it tho if u dont have a wideband obviously ull risk leaning it out, just go through the HI throttle and add/take out fuel where needed until the A/F's are mid-high 11's again.
Understood. however i dont have a wideband. Would any increased richness by adding an exhaust offset the change in octane? I leaned out the a/f mixture by increasing [something] by a few percent over stock. couldnt i just bring it back closer to stock?
 

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yeah if i was in ur shoes i'd add another 2 or 3% every point from 4-7k rpm... but ofcourse wideband is still highly recommended. and also i would drop the boost 1 or 2 psi for extra safety.
 

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RoastBeefCurtain Commando
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from 93-91 I dont think you will really see a difference at all. If you added an exhaust then and were at low 11's, I personally wouldnt even touch it. But thats me.
 

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Discussion Starter · #7 ·
PM-Performance said:
from 93-91 I dont think you will really see a difference at all. If you added an exhaust then and were at low 11's, I personally wouldnt even touch it. But thats me.
I think i was at mid-high 11s before i put the exhaust on. Any other opinions.

I dont know how how to work the s-afc II - any pointers>?
 

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mkiv.com does have a decent write-up regarding the older AFC but it will work for the most part... just alil difference in menu etc. ill give my 2 cents... (dont ask me to be super detailed, my car aint here)

i dont agree w/ the throttle position mkiv.com set... i believe i set mine to low 84% and high 85%. also i think the safc2 gives u 12 pts in the rpm range. watever increments u set, i set the pts around 4-5.5k rpm smaller then the rest cuz i have odb1 and the leanout issue.. so i wanted really richen that area out accurately as possible. hope this helps.
 

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Make sure you have the rpm increments on the afc in thousand increments...1, 2, 3, 4, 5, 6, etc. That is the best way to get a linear smooth power curve. Those who try to tinker at 500 rpm increments and all over the place get a very jagged/ekg curve. Reason being is the ecu is a lil behind. So if the increments are too close and adjustments are made.....the ecu is trying to constantly adjust fuel. If i were you i would add 2-5 % across board at 4k -8k . Better to be too rich then too lean. On average every 1% you add or take away on a afc will affect fjo .1-.2 So if you were 11.8s when you tuned before and weather is similar....then add about 3% across 4-8k range and should put you approx 11.2-11.5 As i said this is approx..but definitely add some fuel. I was on afc for a very very long time with many setups and it responded same way all the time no matter what the setup. And for what its worth you ahould have no adjustments on low throttle setting,. And on high throttle setting 1-3k you should also be at zero. Just once boost comes on and up is only place you need to be adding or adjusting fuel. And as far as obd1 leanout issue....totally a waste of time. It will not HURT ANYTHING. Too many worry about that issue....where i ran over 100k with obd1 "lean area" and never a prob.
 

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Discussion Starter · #11 · (Edited)
The current hi throttle settings which was done at 93 octane, with the assistance of a dyno, and before my exhaust :

4k: -3%
4.6k: -12%
5.2k; -18%
5.8k: - 18%
6.4k: -15%
7k: -12%

For reference before the S-AFC2 this was the a/f mixture on 91 octane and before i got my exhaust;



Also, my notes on a baseline dyno run on 93 indicate an a/f ratio of 10.2.

How much of an effect on a/f will 1lb of boost have? how much of an effect on a/f will 1 octane have?
Do you still think i should go down 2-5% from 4-8k?

THANKS!
 

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Silver Bullet said:
Make sure you have the rpm increments on the afc in thousand increments...1, 2, 3, 4, 5, 6, etc. That is the best way to get a linear smooth power curve. Those who try to tinker at 500 rpm increments and all over the place get a very jagged/ekg curve. Reason being is the ecu is a lil behind. So if the increments are too close and adjustments are made.....the ecu is trying to constantly adjust fuel. If i were you i would add 2-5 % across board at 4k -8k . Better to be too rich then too lean. On average every 1% you add or take away on a afc will affect fjo .1-.2 So if you were 11.8s when you tuned before and weather is similar....then add about 3% across 4-8k range and should put you approx 11.2-11.5 As i said this is approx..but definitely add some fuel. I was on afc for a very very long time with many setups and it responded same way all the time no matter what the setup. And for what its worth you ahould have no adjustments on low throttle setting,. And on high throttle setting 1-3k you should also be at zero. Just once boost comes on and up is only place you need to be adding or adjusting fuel. And as far as obd1 leanout issue....totally a waste of time. It will not HURT ANYTHING. Too many worry about that issue....where i ran over 100k with obd1 "lean area" and never a prob.

Tony,
I had ~13.5 in my "lean" spot which went to around 5K or so, the OBD2 totally cured it. I have my S-AFC set 4,4.5,5,5.5,6,6.5,7 should I just adjust 4,5,6,&7K and get rid of the rest? Also, after going to an aftermarket fuel system, doesnt the "lean" spot go away anyways?
Thanks,
Jason
 
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