Tuning AFR - Lean @ WOT

Performance mods and Advanced Stroker discussion.
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lcolina
Learning to use the board
Learning to use the board
Posts: 36
Joined: May 25th, 2010, 8:25 am
Stroker Displacement: 4.6
Vehicle Year: 1981
Vehicle Make: Jeep
Vehicle Model: CJ7

Tuning AFR - Lean @ WOT

Post by lcolina »

Not sure if I am Dumb, am being fooled by my AFPR, or may be both. Am not a mechanic btw, just an Information Tech guy with a CJ7 for 15 years.

My Setup:
Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom Forged Bulltear Pistons 0.60 20cc
68231-4 camshaft Compcams
0631 head
Mopar/Victor 0.043" head gasket
Mustang Ford Racing 24 pound Fuel Injector M-9593-AA302 with GENSI AFPR
99+ Intake, ODB1 system with MAP sensor from ODB2 and OEM Throttle body.
Standard 98 Block bored to 0.30
Fuel Pump DW200 255 lph.

I removed the MAP Adjuster (from previous stroker) hoping I wont need it.

Tools: Vacuum Gauge, ODB1 Scanner with Live Data, Fuel Pressure Gauge, AFR Gauge.

Symptoms:

If I set the FP to around 35 psi, I have 14.2 AFR with Vacuum Connected, without vacuum around 42. If a rev, FP increases only to 36 for 1 sec then goes to 35-34 psi while 3000 rpm. AFR goes lean. If I set higher FP it will go rich at idle and ok at High revs.

Vacuum is 15-16 "hg (Late timing area in red according to gauge), when revving fast it goes down for 1 sec then goes to 18-20. I tested for leaks, clogging and seems ok.

FP is not increasing with revs/vacuum that's why it goes lean at high revs. If I throttle with a fast move, the Vacuum goes to zero for a second, the FP increases 3-4 PSI at the same time, then goes again to 34 and vacuum gauge shows 18-20

Scanner live data shows timing adv 12-14 at idle, and around 30 at 2600 rpm so I guess timing is ok. Injector PW (ms) 3.7 to 4.0 at idle. Vacuum (V) 2.80-2.84. Map (Torr) 89-104.6

How should vacuum affect FPR? less vacuum more pressure? This seems to be working backwards and varying by 2 psi max. But if I disconnect vacuum FP goes up.

May be this cheap AFPR (I have tried 2 brand new) is not working ok? I am thinking of buying aeromotive 13129 (30-70 PSI).

Is it bad that low vacuum? May be valving problem?

Tomorrow I will take the jeep to make a new fuel line to make sure it doesn't leak.

Haven't checked sparks

Any help appreciated.
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SkylinesSuck
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Posts: 545
Joined: February 14th, 2009, 11:11 pm
Stroker Displacement: 4.6L
Vehicle Year: 1998
Vehicle Make: Jeep
Vehicle Model: Wrangler
Location: Northern VA

Re: Tuning AFR - Lean @ WOT

Post by SkylinesSuck »

Is all of this free revving it in neutral??
bigal389
I made it to triple digits!
I made it to triple digits!
Posts: 102
Joined: February 5th, 2015, 4:55 am
Stroker Displacement: 4.6
Vehicle Year: 2004
Vehicle Make: Jeep
Vehicle Model: Wrangler X

Re: Tuning AFR - Lean @ WOT

Post by bigal389 »

I haven't heard of that brand, try a name brand with vacuum reference and see how that does.
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