Setting the deceleration on the AFC

[body80]

I've read how to set it some many times it's not even funny now.

Can someone Please explain to me how to set the dec. air mode on the s-afc II to run an open BOV.

I'd like to know how to go about setting it and what each value is doing.

Thank you
Jeff

[Hugh]

Start when the car is cold. (after an overnight rest)

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 shoudl 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.

[asad]

Hugh, that's a great explanation of the Dec. Air function.

Asad

[Hugh]

I was going to just type the first part, but he specified he wanted to know what each part did... I had to write a novel about it. I still tried to keep it short and to the point. I can talk for hours about the SAFC.

[nissan_s14]

Whoa...like you read my mind...nice write up.
I have some questions (dont flame pls)

Set my SAFC II to 1.2 % throttle and NE1 3.3 and NE2 4.3
Set the NE's on cold start...lowered it all the way to 1.0 and didnt feel/didnt affect a thing to the idle. I still get a pop (abeit a nice sounding backfire) upon deceleration after some spirited accleration (actually proabably only up to 4k rpm). Should I be setting my NE's lower, or raise my throttle? Or do both?

S13 Blacktop HKS GT2540R and HKSSQV

[Hugh]

Adjusting the throttle isn't going to change anything. I set it at 1% as a place to put it. Basically, if you ever hit the gas at all, it should go over 1%. If you're pressing the gas, you shouldn't need the DEC AIR to be working... so 1% is good. You could probably put it at .1% and it would work just the same.

If you can't make your car shut off by turning NE1 down really low, then something is seriously wrong with what you're doing. You should be able to cut fuel completely there. If you can't get it to idle rough during cold start, then go lower.

The pop you get on decel after spirited acceleration, is this while you're keeping the car in gear and decelerating? A lot of people do that and think something is wrong... when in fact, nothing is wrong. Just push in the clutch and use the brakes when you come down around 2000rpm... no pop.

[Brad]

ive always wanted to know if you could use the dec air function as a cheap way to get some flames on decel. i tried messing around with it and it really didnt do much except make my car drive like crap at idle. although i think i need to mess with it at idle cause i need -15% on fuel just to idle with my 550cc injectors. feels like too much air is coming in.

hmm

[nissan_s14]

The pop you get on decel after spirited acceleration, is this while you're keeping the car in gear and decelerating? A lot of people do that and think something is wrong... when in fact, nothing is wrong. Just push in the clutch and use the brakes when you come down around 2000rpm... no pop.

the pop occurs after i am driving/accelerating to around 4k rpm then i let out the gas and pop the gear in neutral to coast. I can also hear a faint pop when upshifting to the next gear (in btw shifts)

[Hugh]

Decel air can't fix that.

[body80]

Thank you very Much. I have searched the net for hours trying to find a write up on how it works and how to set it up.

You have answered all my Questions.

Thanks again
Jeff

[champa]

hugh is the man! my car runs great except for the idle problem. i'll give this a shot when i get home. thanks bro!

- champa

[Hugh]

Glad to help.