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Setting DEC AIR function on SAFC or SAFCII (stops stalling) |
This is an article I wrote some time ago on Freshalloy about tuning with the SAFC or SAFCII.
Hotwire air flow meter equipped engines do some funky stuff when you
put open air blow off valves on them. The Decel Air function of the
SAFC/SAFCII allows you to correct this. Once you have it set right, the
car should stop backfiring or stalling on deceleration.
Start when the car is cold. (after an overnight rest is the best way, but at least several hours without running)
Turn key on, go to decel air settings.
Set throttle to 1%.
Set NE1 to about 4.
Set NE2 to about 5.
Start car.
Adjust NE1 until you get a smooth idle while the engine is still
cold. Now start turning it down as low as possible while still
maintaining a good idle.
If the car starts sputtering and getting rough, you just went too
low. Turn it back up very slowly until it smooths out. You want to
leave NE1 on the lowest possible point with a good idle.
Now set NE2 to be about 1 higher than NE1.
This formula should eliminate any stalling or popping from the BOV being open.
Theory: Throttle setting tells the SAFC whenever the pedal is
depressed less than 1%, the SAFC should control fuel and ignore
everything else (including the MAF)
NE1 is the first RPM point you have selected in your NE Point
settings. I put mine at 1000 rpm. I set NE2 at 3000, then NE3 at 4000,
and so on in 1000 increments. Setting NE1 down at 1000 gives you the
ability to control fuel at idle really well. Besides, you probably
don't need to adjust anything between 1000 and 3000. (turbo spools
after that, right?)
Setting the air flow percentage at NE1 is basically telling the
SAFC a number to use whenever it reaches that RPM and less than the
throttle setting. So, as the throttle is let off, the SAFC looks at the
NE1 and NE2 points. As RPM rolls back, there is going to be a reduction
in air into the engine, yet the MAF has already seen it. The stock ECU
is attempting to send the fuel for that air that is now missing...
hence your stalling and backfiring. The SAFC catches that signal,
ignores it, then tells the ECU exactly how much air flow you have
according to your DEC AIR settings at those RPM points. Get it?
RPM comes down, hits NE2, SAFC sees 10%. It tells the ECU it needs
5%. (because you picked that number.) Now the RPM won't dive so hard
like it was. It reaches NE1, SAFC sees 6%, you told it 4% and it tells
the computer only 4%. The idle sets steadily down to where its supposed
to and everybody is happy.
The SAFC is all about tricking the ECU into doing what you want it to. |
Tech 