safc adding and subtracting fuel
 

I have a s5 tII with a rtek 1.8 , 720cc, 780cc that im trying to get tuned out. i have a lc-1 to watch the afr's and the safc to alter the fuel. At idle, afr's are reading 12's and i tried to lean it out a bit but the safc confuses me. I have it set 10% low and 50% high. I tried to lean the idle out, but i want to make sure im doing it the correct way. If i add correction %, does this add fuel or remove it? Or is it the other way around.

+1% is adding more air which makes it lean
-1% removes air which makes it more rich

Setting low 10%, high 50% means low throttle settings are from 10%-49%, high throttle will be 50%-100%

When you idle, if the tps and the idle screw is in spec (assuming 750rpm idle), the safc should be showing 0 on throttle. With your current setting dosen't matter how much % you alter it will should have no effect on idle. To play with the idle, you should adjust the throttle setting to low 0%, high to whatever you desire.

Safc only alters the air, you should be tuning based on the fuel and make the adjustment on the air.

it shows 0% throttle at idle.

Im having to go all the way up to +20% and then some to get in the 14's at some ranges. the real question that i should be asking here is what should i set it to for boost to be safe.

Depends on your mods and condition of your engine, i have a similar setup as you with 720prim/720sec, I have idle at 14.7(I have to put it up to +12 as well to settle at 14.7), 13.8 on cruising/light throttle, and i aimed at 11.5 under full boost but thats just me. From what i read and tested myself 11.8 should be the leanest you go underboost, some people stay at low 11 just to be safe.


And interms of how much % that is on your safc, that can be vary on different cars. Just play with the numbers on the air map until you hit the desire AFR you want.


Just a note, you don't want to have the AFR too close to perfect on low rpm (under 3800), since the secondary doesn't kick in until that range, if you are going uphill on low rpm and boost kicks in, you might get a dangerously lean AFR. (Well i have my meth injection kick in and richen it back down when it happens too me).




But first thing first, it is highly recommanded that you put the car on a dyno and get the initial numbers tuned. Since trying to monitor the AFR while driving on the road (especially in high rpm range and full boost) is umm... dangerous :lol: