First of all, its accepted that maf voltage effects the timing map and fuel map. So tricking the ecu through the maf when leaning out injectors will advance your timing accordingly.

A vafc controlls fuel by modifying MAP only. It will covert the signal from one type of maf to another types signal eg.300zx to a32.

Do you still get the timing map and performance increase of modifying MAP signal to lean out the injectors? Like say..... A vafc2 pulling 15% fuel via the MAP sensor across the board VS an safc2 pulling the same fuel via the MAF sensor.

For all this to work, its based on the fact that our cars use both the map and maf to tune wot. I was unaware of this untill today unless someone has proof otherwise.

 

I wish I could help but this is over my head for sure.
The all motor section might be of better help sorry

 

in fo' info.

 

our car does not have a MAP sensor unless you added one...

 

It has a MAP/baro sensor. I've gotten the code lol. But I called apexi and the vafc only tunes using the MAP sensor. And I am using a vafc2 on my max..... Splain that.

 

Tech support at Apex-i said "the vafc controls fuel by modifying the MAP sensor voltage because it is designed to work primarily for Honda vehicles, which are tuned through MAP. If you have found a way to make it work for a MAF car more power to you, but the VAFC is not designed to modify MAF voltage."

 

No, that's not correct. our car has MAP/Baro solenoids which are not the same as a MAP sensor used for tuning. A map/baro solenoid is a solenoid (a switch) which flips back and forth in response to a signal FROM the ECU. It switches a vacuum line from atmospheric pressure to manifold pressure. It does not have a "voltage output" of any kind like a manifold absolute pressure (MAP) sensor does - it receives a current and flips a switch, that is all. Input only - no output.

A MAP sensor is a sensor that senses changes in pressure due to throttle plate position, engine speed, etc, and then sends a varying voltage signal signal OUT to the ECU (or VAFC) to let the ECU know how much air is going in to the engine, so the ECU can then choose how much fuel to give to the engine.

They have a similar name, but are not related in any way.

The only way to TUNE our car with a MAP sensor is to add one with an engine management which supports it, such as emanage, or a standalone, etc.

 

so is the pressure reading on the vafc fake? I show -9ish psi at idle, around 0 at cruising. and +12ish at WOT. What is that reading from?

 

how would you have 12psi of positive pressure unless you are turbo or supercharged?

it is just reading a voltage from whatever sensor you have it hooked up to, and is translating that into a value that it thinks is correct. for instance if you have it set up for a certain honda MAP sensor that reads say 4.0V at 12psi of boost, but you have a MAF voltage of 4.0V going into the VAFC... the VAFC doesn't know what sort of sensor you have hooked up to it. all it sees is a voltage number and then it translates that to whatever sort of sensor it believes you have hooked up to it. that's why on engine managements you have to set up what sort of sensor you are using, different sensors output different voltages and if your engine management thinks you are seeing 12psi of boost and adjusts fuel and timing accordingly, but you're really NA... well, that's obviously going to affect things in a negative way.

 

makes a little more sense now. it seems weird that the company doesnt know that a vafc will control MAF's like a SAFC