afm tuning!!!

[Guest lamar32]

what will be the ill effescts if you just turn the afm wheel counter clockwise as tight as it could go that would be as rich as you could get it correct. The reason I'm asking is recently I installed a new fuel supply line and used the old line as a return as a result my fuel pressure drop from about 80psi to about 36psi but now when I 'm in it I can can hear it ping a little the car runs alot better on the lower endas a result of the new fuel line, but I want to richen it up.

[Organdonor]

go here for a good explanation. http://www.hammondsplains.com/zclub/techtips/

[Clifton]

Wow, you must of had a small return line. If you go tight it would lean it out. How do you know your "ping" isn't from timing. You would have to be pretty lean to get a rattle. As for adjusting the wheel. If left alone it would open at peak torque at WOT, 3000-3500rpms. I've tested other flapper door AFMs but not on an L28. If you soften it to richen it up it will just be richer until you reach the point when it evens out again, 3000-3500rpm, then it will be as it was stock. You say it runs better no. It doesn't sound to lean then. I would back the timing off a little, maybe 2*. If you are determend to richen it up I'd get an adjustable FPR.

 

 

Clifton

[Guest bastaad525]

Most likely tuning your AFM will NOT get rid of any ping you have if it's occuring over 4000rpm. It's been shown time and again that the AFM is pretty much open as far as it will open, at wide open throttle, by about 4000rpm, and just doesn't effect fuel flow after that. Basically the ECU just switches to a preprogramed fuel curve based only on RPM, and maybe a few other inputs, like the head temp sensor, and runs the amount of fuel it thinks is 'safe' above that rpm. Problem is, that of course the ECU has no way of knowing if you've turned the boost up. So if you're running higher boost, or an intercooler, or such where you're getting more air/oxygen into the cylinders, you will run lean. I dynoed my car, stock fuel pressure, an MSD pump though, so it definately was keepign up the fuel supply, but after around 4500rpm it leans out a LOT, enough to be dangerous. I've also seen about four other dyno charts now of guys running the stock ECU and it's ALWAYS the same thing, super rich up to 4000rpm (because the AFM can measure the increased boost at that point) and dramatic leaning after that.

 

I agree that you should try backing off your timing, just to play it safe for now. OR, a better idea, is get some way to richen up the fuel on the top end. This is what I"ll be doing next. I'm going to get an adjustable fuel pressure regulator (MSD part #2222, adjustable FPR with boost reference, can be had as low as $55), up the fuel pressure however much it takes to get the top end down to a safe 12:1 air/fuel ratio, and THEN I'll tweak the AFM, tighten it up to lean out the midrange and compensate for the richer, higher fuel pressure (as I said it already runs super rich in the mid range, obviously upping the fuel pressure will make it even worse). I'll be doing this on a dyno with a wideband exhaust sensor, which is really the best and only way to do this and be safe, AND get the best power as well. Another option, is to go with larger injectors. Really, there are no other good, reliable ways to get more fuel on the top end running the stock ECU. And they ALWAYS run lean on top once you start upping the boost. There is one other trick that some guys have used using an adjustable resistor inline with the head temp sensor, but I've heard this is good for only minimal adjustments. Anyways, hope this info helps.