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7mge-t going lean when i let off throttle

2.1K views 7 replies 6 participants last post by  suprarx7nut  
#1 ·
here's the setup:
440cc injectors
7mge electronics
apexi safc
stock ct26 turbo
I tuned the safc to idle and run at about 12AFR, however when i let off the throttle it goes very lean. If i keep the gas on and let of slow it's fine stays right around the 12 that i set it at.
Any suggestions on what i can do to resolve this problem.
I have played with the safc and havent really found a way to keep it from going lean.
 
#2 · (Edited)
As far as I know, that's how it should be because the ECU cut fuel. The ECU cuts fuel faster than the air because fuel delivery is done by electricity which is instant, while the mechanical closing of the butterfly to the throttle body isn't. The ECU recognizes all of a sudden it is lean and corrects it almost immediately after. Sounds like normal operation to me. It wouldn't be normal if it stayed lean for more than a few seconds. How lean are you talking? Anything under 15 is safe
 
#4 ·
Saves fuel, cuts emissions, bla, bla, bla.
Same thing can be programed into aftermarket stand-alones.
But I am not doing it on my Haltech, as I want big popping flames out the exhaust when I let off the go peddal :)

And the only time you want 12:1 on a na/t is under moderate load/ light boost.
Under full throttle it needs to be richer than that, say 11:1 for medium bost like 10psi, and 10:1 for big boost numbers.
Idle & just rolling down the highway, you want to be at 14-15:1

12:1 is great for a na under heavy load, but not a boosted engine where you need the extra fuel to control detination.
 
#5 ·
Is there a proper venting system on the car at all. Blow-off valve, Bypass Valve, recirculated? Also, just food for though. Go over the IACV (Idle Air Control Valve). Maybe there's a differences in that between the GE, and GTE. Anyone know for sure?
 
#6 ·
Yes, I have a hks ssqv. And it goes way lean maxes out my wideband, which is 22.4. If I slowly let off the throttle its fine. Bov is working. I heard if you don't have a recirculating bov it can do something along those lines
 
#7 ·
That is correct. Check your idle air control next. While your there just go over all the piping and make sure everything is tight. If possible pressure test the system also. it doesn't take long and is super simple.
 
#8 ·
OP: What you explain is not a problem. That's how the OEM ECU works. It sounds like your only problem is an extra rich idle from the SAFC.

Coasting above idle RPM: very lean
Idle and light load: 14-15
medium and heavy load: 12 or lower