so im looking into buying a vafc. just for the facto control vtec. i can get a good deal on one.but is it worth putting in i allready have a chipped p28 thats tunned with uberdata is it worth getting it or not.

 

I'll quote this again:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pgmfi.org &raquo;</TD></TR><TR><TD CLASS="quote">Why piggybacks (vafc, emanage) "suck"

Piggy Back controllers allow stock ECUs to do things that they normally can't do, like run larger injectors or deal with boost. Remember that piggyback controllers work by altering sensor signals before they get to the ECU.

Most of the time, the primary signal being messed with is the Map Sensor. This is critically important in a Speed Density car. The Map Sensor is used by the ECU to guess how much air is going into the car, and therefore how much fuel to supply in order to match airflow. When you "lean" out a car with an AFC, you are simply decreasing the Map Sensor signal - the ECU responds to the decrease in manifold pressure by supplying less fuel. When you "richen" a car with an AFC, you are simply increasing the Map Sensor signal - the ECU responds to the increase in manifold pressure by supplying more fuel.

The change in fueling happens for a reason: if you look at a fuel table, Map Sensor values correspond with columns. When you increase or decrease the signal from the Map Sensor, you are simply making the ECU use a different column than it originally would have used. (see Understanding Maps if you need some help understanding reading Fuel and Ign tables)

But wait, isn't the Map Sensor used for determining ignition requirements too? When you "lean" out a car with a Piggy Back, you also in all likelyhood advanced timing. When you "richen" a car with a Piggy Back, you also in all likelyhood retarded timing. Look at trends horizontally (as MAP changes) in an ignition table, and you will see why this happens. This helps explain why so many boosted cars running on the "AFC hack" have issues due to excessive ignition advance.

The bottom line: Piggy Back Controllers suck because you cannot independently adjust fuel and ignition. Any changes to fueling will produce a change in ignition too, and often this is undesirable.</TD></TR></TABLE>

 

I have a 00 si with a vafc-1 in it and im not pleased with it.. I cant really tell to much of a difference exp. wheni changed the break point of vtec..... I bought a chipped p28 and im glad i did.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2000siturboR &raquo;</TD></TR><TR><TD CLASS="quote">so im looking into buying a vafc. just for the facto control vtec. i can get a good deal on one.but is it worth putting in i allready have a chipped p28 thats tunned with uberdata is it worth getting it or not.</TD></TR></TABLE>

Changing your vtec crossover on a pre-tuned chipped ECU doesn't make any sense. It doesn't adjust your fuel curve. Retune your ECU.

I run a VAFC with 0% modifications because it's a (relatively) cheap digital output for info like throttle, mani pressure, etc so you don't have to rely on a cluster of gauges.

 

i thnk vfac was a waste of my money

 

No, it's a waste of money.

AFC's are only useful for the AFC hack on a turbocharged car, and even then they are still a waste of money since uberdata is free.