It does use the sensors , But the sensors need a table to reference . This table is effected by the fuel trims . Because all the VAFC does is tell the ecu that the air flow has changed.

....



What is it good for one asks. Ultimately the VAFC can correct fuel trims for mods that effect AFR getting them to back to 0 . Fuel trims floating around 0 means the ecu is happy . It is just as it claims , a fuel controller . You can use it to scale different injectors and to correct fuel trims nothing more.

But trying to lean out the car to make more power will effect fuel trim and the ECU will compensate for it . Plus it is not good for the engine . I see poeple saying they got back from the dyno and gain 10hp but there AFR is 13.9 at WOT This is not the way to make power . Plus now you are prone to knock and the ECU will just pull timing anyway . A one gear pull at WOT on the Dyno is not the same as rowing 5 gears at WOT on the highway .


So whats the difference with other ECU's

The way the Amuse , Mugen , AEM makes power as they dont need to comply with US regulations and they change the ECU target AFR to anything they like and can control timing . But only the AEM is user adjustable and can compensate for different mods . The pre programed race ecus were tuned most likely with the manufactures specific mods


The way the Greddy Ultimate works, is it post processes everything so the ECU is not being trick at all .Just satisfy the fuel trims and start tuning . You still cant tune for PT throttle AFR'r as the factory ECU is still trying to keep things at 14.7 . but you can change timing to make it have snappier throttle response .


To be able to tune the Vafc or the Greddy or any piggyback properly you will NEED and OBD2 scan tool that can read fuel trim .This is not the same as reading the AFR's with a wide band.

 

^^^^good info. but remeber too that all engines are a little different. my vafc is set to 13.8-13.9@WOT and my car doesnt knock, ping or any of the usual detonation type of symptons. i would have never set it that way, but through HOURS of dyno tuning we deduced that the car is perfectly safe where its safe. i would NEVER recomend anyone else to shoot for such a lean AFR, it just works for me.

i wish you where near me twizted, i want emange in the worse way, and for you to tune it! your always a vault of info twizted

 

CAN I HAVE MY 20 MINUTES BACK?

 

One of the main reasons I want to tune my VAFC 2 is to lean it out a bit..It will be nice to add a little power, but I don't like having to wash my car every other day because of the black shit on the back of my car...I also had the VAFC 2 on my Si and it made some nice numbers, but I had head/Valve work and other mods...We'll see how it goes

 

under WOT the ecu is in open loop mode and only referencing the predefined fuel and timing tables. There is no O2 feedback at this point, so if you're lean you're lean, the ECU cannot correct you at this point. This is one of the "drawbacks" if you will of a MAP based system vs MAF, because actual airflow is not being measured. This is also why intake and exhaust pick up power on these cars, because you not only increase the volumetric effeciency of the engine but you essentially lean the AF ratio out under WOT due to the increased airflow. Once closed loop operation has adjusted the fuel trims properly for part throttle driving your open loop fueling is almost set in stone.

Its true that the fuel trims can ultimately have some affect on fuel at WOT, but those fuel trims are adjusted during closed loop operation at part throttle, and once they have learned your car your WOT AFR isn't going to vary much.

If I lean my car out to a 15.0:1 AFR under WOT then its going to pretty much stay there, fuel trims aren't going to bring that down into the low 13s.........

 

I'm getting ready to install my VAFC as well with the boomslang harness, but where the heck is the ECU? It seems like this thread has gotten off the topic of how this guy wants help on installing his VAFC and on the topic of talking 5h1t. just help the guy out.... and me too :-)

 

Also on my settings, would I have to set my throttle settings like everyone elses, lo-10% hi-50% or could i just set it for WOT? Thanks

 

any results yet?

 

Not yet...My tuner postponed my tune until next month..I'm still at school anyways, so i wouldn't have been able to go home when the first tune was scheduled anyways...I'll let you guys know when I'm able to tune it..

 

thanks! Goodluck on the install. subscribed.