Need help with 420a tuning and SAFCII

[Locke]

Be aware of the thread's title, "420a tuning".

ld just like to say who ever started the idea that the SAFCII DOESN'T add fuel is wrong. IT does add fuel and it does take fuel out. it does both. Sorry for waking up an old thread but im sure people are reading this and getting wrong info. "The SUPER AFC II is a fuel adjustment controller in which the airflow sensor signal or the
pressure sensor signal can be modified in a 12 point RPM range by 1% increments to
increase/decrease fuel in a range of +50% to –50%." straight from the manual.

:sigh:

The 420a uses a speed density system of metering air, and as such uses a MAP sensor. Since the engine was designed to be naturally aspirated, no fuel or spark maps were made to support positive intake pressures. Fuel is cut at the onset of positive pressure.

So far, the SAFC will function as advertised.

Then we add boost. In order to prevent fuel cut, we must trick the ECU into not seeing the boost. To do this, we employ either a Missing Link, (abbr. "ML"; check valve with vent which prevents the MAP from seeing positive pressure) or a Fuel Cut Defender. (abbr. "FCD"; a solid state electronic device which intercepts the MAP signal, and clamps it at a defined level, preventing the ECU from reading boost) With such a device, you are unable to increase the MAP signal above what would be the lower limit of fuel cut, near 0psi. We then tune for fuel by other (usually mechanical) means.

Thusly, you cannot add fuel in boost with an SAFC on a 2gnt.

 

[90gsx16g]

Be aware of the thread's title, "420a tuning".



:sigh:

The 420a uses a speed density system of metering air, and as such uses a MAP sensor. Since the engine was designed to be naturally aspirated, no fuel or spark maps were made to support positive intake pressures. Fuel is cut at the onset of positive pressure.

So far, the SAFC will function as advertised.

Then we add boost. In order to prevent fuel cut, we must trick the ECU into not seeing the boost. To do this, we employ either a Missing Link, (abbr. "ML"; check valve with vent which prevents the MAP from seeing positive pressure) or a Fuel Cut Defender. (abbr. "FCD"; a solid state electronic device which intercepts the MAP signal, and clamps it at a defined level, preventing the ECU from reading boost) With such a device, you are unable to increase the MAP signal above what would be the lower limit of fuel cut, near 0psi. We then tune for fuel by other (usually mechanical) means.

Thusly, you cannot add fuel in boost with an SAFC on a 2gnt.

Alright i see, but does it do the same for a turbo? Asin does it add/ take fuel or does it just hide air from the ecu? I thought for turbos it would add fuel too.

 

[VelocitàPaola]

4G63 DSMs do not use a speed density system for interpreting air flow; they directly measure it using air flow meters. Additionally, the calculations affecting fuel consumption are based upon reading from the MAF throughout both vacuum and boost, so the S-AFC is much more useful in this case.

There is a way to hack the S-AFC using a MAP sensor as a replacement input for the usual TPS input, but the gains compared to the cost of an S-AFC aren't significant.

 

[90gsx16g]

4G63 DSMs do not use a speed density system for interpreting air flow; they directly measure it using air flow meters. Additionally, the calculations affecting fuel consumption are based upon reading from the MAF throughout both vacuum and boost, so the S-AFC is much more useful in this case.

There is a way to hack the S-AFC using a MAP sensor as a replacement input for the usual TPS input, but the gains compared to the cost of an S-AFC aren't significant.

Alright thanks for clearing that up, i thought he was saying that the safc was useless for all aplications. I knew 4g63's used a different air metering system, i was just confused on some points. Thanks for the info, i apologize for comin in perty strong on my thoughts.

just a thought... would anyone be ably to help me witht the settings on my S-AFCII ? My Eprom ecu that came witht the car fried out and i had to put a stock one in ( lost all my settings since i changed out battery too. know idea what the guy had it set to befor me). I dont wanna build off this thread so if you could PM me that would greatly apreciated

 

[VelocitàPaola]

Start a new thread in a 4G63 section for your questions...

 

[95AWD_TSI_TALON]

I know this threads old but got a question. I am working on a guys 420a turbo car, long story short, car was bought with blown boosted motor. I see it has a Jet ecu, vortec FMU, aeromotive fpr, safc, and some splitsec.com thing. My first thought were WOW. Now I see the 420a's are nothing but piggyback crazy.

For tuning, couldn't I just run the safc to a seperate map sensor (gm 3bar) and then that would see up to 28psi and the ecu would never see it. As it would be running on the stock map still.
Matt

 

[VelocitàPaola]

I know this threads old but got a question. I am working on a guys 420a turbo car, long story short, car was bought with blown boosted motor. I see it has a Jet ecu, vortec FMU, aeromotive fpr, safc, and some splitsec.com thing. My first thought were WOW. Now I see the 420a's are nothing but piggyback crazy.

For tuning, couldn't I just run the safc to a seperate map sensor (gm 3bar) and then that would see up to 28psi and the ecu would never see it. As it would be running on the stock map still.
Matt

It doesn't work like that. The S-AFC works by modifying the stock MAP sensor signal before. This modified signal is then modified and sent to the stock PCM. You can't simply use a different MAP sensor; it would confuse the PCM since the stock and GM MAP sensors use vastly different scales.

You can, however, replace the S-AFC's TPS input with the signal from a GM or other MAP sensor. This is a real old-school modification developed by Corbin on 2GNT:

2GNT.com - SAFC_fuel_Compensation_Based_on_Boost


420A's aren't "piggback crazy" as you say. The JET chip is trash, so throw that away. Even with the above mentioned modification, the usefulness of the S-AFC II is questionable, so you can remove that too.

The Split Second device is probably an FCD, so keep that. The FMU and AFPR can both be replaced with an S-FMU which will afford you much greater tune-ability.