air/fuel ratio Question

Performance mods and Advanced Stroker discussion.
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YJason
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air/fuel ratio Question

Post by YJason »

Is this normal AFR on a 4.6 stroker or do I need to build an adjustable MAP? I just got it running a week ago and I'm wanting to get my AFR where it needs to be.

Fuel pressure steady ~50 psi at the fuel rail (it may drop to 49 psi when reving)

Idle 15.0-15.4:1 ( liveable )
while driving a steady pace 1800-2600 rpm 14.4-14.9:1 ( IMO perfect )
WOT 11.9-12.4:1 ( normal or too rich )

Just in case you want to know:
I'm using a Autometer digital A/F guage to get my ratio data
CIA fairly new (it sucks a lot of hot air)
Aftermarket 62mm TB (not a bored one)
stock replacement 24lb bosch injectors (96 XJ)
1999 up intake
Borla split header, 2-2" pipes down to a 3" back to a Flowmaster 50 series and 2 1/2" out the back.
Stock coil
new cap, rotor, and plugs (Autolite 985)
MSD 8.5 mm wires
COMP CAM 68-231-4
Gasket match port and polish to the head and intake
.030 over Hypereutectic pistons
4.2 3727 4 counterweight crank
4.2 rods
0630 96 XJ Head
96 XJ Block
Its all controlled by a 96 XJ ECM
SIXPAK
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Re: air/fuel ratio Question

Post by SIXPAK »

Not sure of the steady state driving but your WOT looks great IMO. Play with the WOT to see what the motor wants.If you get to 13.5 WOT I think you could be gatting a bit on the lean side, be careful. My race motor seems to like from 11.8 to 13.
dwg86
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Re: air/fuel ratio Question

Post by dwg86 »

Nubers look good. Do you have a part number for the injectors?
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SilverXJ
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Re: air/fuel ratio Question

Post by SilverXJ »

WOT is a bit rich, but nothing to worry about. The other numbers are normal and can not be changed anyhow.
hatem61
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Re: air/fuel ratio Question

Post by hatem61 »

WOT seems okay. We have to bear in mind that at WOT, the PCM does not adjust the A/F ratio, instead it it uses preset values.
YJason
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Re: air/fuel ratio Question

Post by YJason »

dwg86 wrote:Nubers look good. Do you have a part number for the injectors?
No part # but I called this place and told them I had 4.6 stroker and he sounded familar with jeep stroker motors.

http://www.southbayfuelinjectors.com/
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SilverXJ
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Re: air/fuel ratio Question

Post by SilverXJ »

hatem61 wrote:WOT seems okay. We have to bear in mind that at WOT, the PCM does not adjust the A/F ratio, instead it it uses preset values.
Yes, but that is where it can be adjusted by a piggy back tuner or simple map adjuster.
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Cheromaniac
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Re: air/fuel ratio Question

Post by Cheromaniac »

YJason wrote:Is this normal AFR on a 4.6 stroker or do I need to build an adjustable MAP? I just got it running a week ago and I'm wanting to get my AFR where it needs to be.

Fuel pressure steady ~50 psi at the fuel rail (it may drop to 49 psi when reving)

Idle 15.0-15.4:1 ( liveable )
while driving a steady pace 1800-2600 rpm 14.4-14.9:1 ( IMO perfect )
WOT 11.9-12.4:1 ( normal or too rich )
Looks good to me. WOT is a bit rich but acceptable. Above 4000rpm my stroker's A/F ratios at WOT are similar. You can leave yours well alone.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :lol:
YJason
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Re: air/fuel ratio Question

Post by YJason »

SilverXJ wrote:
hatem61 wrote:WOT seems okay. We have to bear in mind that at WOT, the PCM does not adjust the A/F ratio, instead it it uses preset values.
Yes, but that is where it can be adjusted by a piggy back tuner or simple map adjuster.
Dumb question, where is the MAP sensor on a 96 XJ?

I'm getting a little pinging with 93 octane on semi steep inclines while in OD. Would the AF bouncing around 14.9-15.2 at 2100-2200 RPM's be causing the pinging??
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