Re: AFM Adjustment
Posted: Mon May 07, 2012 7:47 pm
1978 Bus AFM Adjustment Results
posted April 2011
This original factory build engine has original exhaust and fuel injection at 69,000 miles just this morning.
Compression most recently was 130/135/125/140. No valve seat migration noted in the before/after hydraulic valve adjustment check. (1 1/2 preload)
Ambient temps 84* no wind, Interstate 10 westbound in Florida and Interstate 75 northbound to Atlanta GA.
My original AFM adjustments were set in Yuma, AZ in February to yield a 12.5 air/fuel ratio at full throttle at 3,000 rpm and a 70 mph cruise at 13.5. The car has been driven hard for the last 4,000 miles with these settings.
The AFM adjustments below are in reference to the above "base line". The "A" adjustment is the wiper which has little teeth to reference (originally at 3-3/4 teeth from base point, so less than that is leaner), and the "B" adjustment is the black cog with the number of teeth increments from my baseline (+ is CCW towards rich). Idle mixture screw "C" number is from seated position, more is leaner.
....MPH........A........B.........C........CHT........A/F..........MPG.........notes
.....65........2.5.......7+.......2.5.......415........15.7........................pinging!
.....70.........................................435........15.6.....................................
.....75..........................................NO........................
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........2.5......14+.......3..........420.........14.4..................................
.....70...........................................430.........13.6..................................
.....75...........................................447.........13.4..................................
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65.........3..........0........2.5........406.........14.1...................................
.....70...........................................435.........13.8...................................
.....75............................................NO................................ 450* CHT
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........3.5.......6+....................400.........11.9.....................idle 15.5
.....70............................................413................................................
.....75........................................................................................no test
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........3.75.....3+.......3.5........385..........11.7..................................
.....70...........................................400..........11.6..................................
.....75...........................................410......................................63*amb
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4........6-.........2.5.......400.........11.9........................idle 18
.....70...........................................416..........11.8.................................
.....75...........................................447..........12.0....(full throttle hill)......
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4........6+.......4.5.......393..........11.5.........17.5.....using the
.....70...........................................398.........11.3.......itinerant-air-cooled
.....78............................................424.........11.3.......................method
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4.........0.....................385.........11.4.........17.3........63*amb
.....70............................................395.........11.4.................................
.....75............................................415........11.4..................................
*************************************************** 81*amb
......65...........................................395.................................................
......70...........................................410.................................................
......75...........................................425.................................................
I have some guesswork conclusions from the above, but look forward to any wonks chiming in. The only critical conclusion I came up with was
Do Not Assume! I ran the LM-1 at a PigRich 11.4 expecting horrible fuel economy, and instead got the best fuel economy and the lowest CHT readings!
Colin
posted April 2011
This original factory build engine has original exhaust and fuel injection at 69,000 miles just this morning.
Compression most recently was 130/135/125/140. No valve seat migration noted in the before/after hydraulic valve adjustment check. (1 1/2 preload)
Ambient temps 84* no wind, Interstate 10 westbound in Florida and Interstate 75 northbound to Atlanta GA.
My original AFM adjustments were set in Yuma, AZ in February to yield a 12.5 air/fuel ratio at full throttle at 3,000 rpm and a 70 mph cruise at 13.5. The car has been driven hard for the last 4,000 miles with these settings.
The AFM adjustments below are in reference to the above "base line". The "A" adjustment is the wiper which has little teeth to reference (originally at 3-3/4 teeth from base point, so less than that is leaner), and the "B" adjustment is the black cog with the number of teeth increments from my baseline (+ is CCW towards rich). Idle mixture screw "C" number is from seated position, more is leaner.
....MPH........A........B.........C........CHT........A/F..........MPG.........notes
.....65........2.5.......7+.......2.5.......415........15.7........................pinging!
.....70.........................................435........15.6.....................................
.....75..........................................NO........................
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........2.5......14+.......3..........420.........14.4..................................
.....70...........................................430.........13.6..................................
.....75...........................................447.........13.4..................................
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65.........3..........0........2.5........406.........14.1...................................
.....70...........................................435.........13.8...................................
.....75............................................NO................................ 450* CHT
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........3.5.......6+....................400.........11.9.....................idle 15.5
.....70............................................413................................................
.....75........................................................................................no test
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........3.75.....3+.......3.5........385..........11.7..................................
.....70...........................................400..........11.6..................................
.....75...........................................410......................................63*amb
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4........6-.........2.5.......400.........11.9........................idle 18
.....70...........................................416..........11.8.................................
.....75...........................................447..........12.0....(full throttle hill)......
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4........6+.......4.5.......393..........11.5.........17.5.....using the
.....70...........................................398.........11.3.......itinerant-air-cooled
.....78............................................424.........11.3.......................method
....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4.........0.....................385.........11.4.........17.3........63*amb
.....70............................................395.........11.4.................................
.....75............................................415........11.4..................................
*************************************************** 81*amb
......65...........................................395.................................................
......70...........................................410.................................................
......75...........................................425.................................................
I have some guesswork conclusions from the above, but look forward to any wonks chiming in. The only critical conclusion I came up with was
Do Not Assume! I ran the LM-1 at a PigRich 11.4 expecting horrible fuel economy, and instead got the best fuel economy and the lowest CHT readings!
Colin