VF test results

[damone]

I decided to test the a/f via the VF signal today, maybe someone could help me out with the results.. BTW, my diagnostic port has a VF1 and a VF2.. I used the VF1 does it matter??


At idle, cruising, and light throttle im getting 5v - Maximum rich.. So the engine is running lean and the TCCS is dumping extra fuel in.. OK

Mid throttle, up to 2psi it reads 3.5V - Minimum rich, so its gettin better..

As soon as I hit ~60-70% throttle, or anything higher than 2psi it goes right to 0v, Maximum lean..

Running completly stock fuel system and stock AFM.. mods are 57trim ct-26, 3" BIC exhaust to stock muffler, and custom air intake with hardpipes..

is this normal? is there any way to straighten it out a little w/o risking engine damage? or w/o spending a pile of $$$ BTW, i do not have dyno access.. Since its already lean at idle, I didnt want to back the screw out of the AFM

[bgrieger]

Hard throttle (can't remember the exact cutoff) results in closed mode running, and VF isn't employed in tune. The computer relies on the stored map at that point.

I'd give it more screw and try to richen it up a hair at the bottom to mid, and not worry about the upper end. Without a dyno or wideband, you're only putting the motor at risk playing with tune. VF is a very narrow range of tune, and a couple of percent one way or the other are the difference between lean and rich here.

You could and should consider investing in the wideband if you have no dyno access, and use an SAFC or similar to tune...of course, never to the ragged edge. For home brewed tuning even with a wideband, I recommend staying safer than you would like tune on a dyno, but I don't like paying to replace motors all the time either...