Air to fuel ration - MustangForums.com


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Old 06-21-2014, 11:06 PM   #1
yurizx6r
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Default Air to fuel ration

Hey guys, I just put in an air/fuel gauge wide band in my 93 5.0. I am new at air to fuel ratio's, but after driving it for 5 miles (after unplugging the battery) I noticed that if I drive it normal the a/f ratio goes between 14.5-15. This is shifting at about 2800 RPM's. When I put the petal to the metal (WOT) my higest number goes up to 17 and my lowest number was 11.3...........problem? When you mash the gas and shift it at 5,000 it seems to be running lean. I know for turbo cars you don't want that number any higher than 11.5, but I don't know about our cars/naturally aspirated engines. Thoughts?
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Old 06-21-2014, 11:09 PM   #2
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In case this makes any difference here are my mod's worth mentioning to the motor: bama chip with EGR delete, BBK CAI, C&L 73mm MAF, 70mm TB, Trick Flow Track heat intake, stock injectors, and a full exhaust with long tube headers and off road H-pipe.
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Old 06-22-2014, 07:53 AM   #3
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Stupid question for you ,but that C&L MAF housing doesn't have a sample tube set up for larger injectors does it?
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Old 06-22-2014, 08:55 AM   #4
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No. It's set up for 19lbl injectors, and I even checked with C&L what the dimensions were. They were measured with a pair of calipers, so I know for sure it's good.
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Old 06-22-2014, 09:26 AM   #5
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when are you seeing 17 and when are you seeing the 11.3? where is it at were you think it is lean?
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Old 06-22-2014, 10:16 AM   #6
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Ok let me start over. What are the normal ranges for a naturally aspirated car like ours? What numbers should I see and when? I am thinking new that maybe I should give the computer some more time to learn the tunes after unplugging the batter, and the fact that I kept switching tunes on my Bama chip probably didn't give it enough time either.

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Old 06-22-2014, 11:18 AM   #7
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To answer your most recent question, those "numbers" are all in the "normal-ish" range. At 2k rpm steady my car was around 17 on the dyno. When matted it dropped to 13-ish and pretty much stayed right there all the way though the pull up to 5500rpm. That's with a stock fuel system, stock A9L, and an SN-95 MAF housing.

If you see 17 during WOT, something is WRONG. A number like 11 as soon as you step off the gas is normal but it should clean up quick.
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Old 06-22-2014, 01:26 PM   #8
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Just cruising, it should be roughly 14.7 (controlled by the O2 sensors). For wide open throttle, for NA, it should be roughly 13.0:1.
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Old 06-22-2014, 04:46 PM   #9
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Ok so during WOT it would go down to 11.3, but as soon as I let off the throttle and went to idle it went to 17 then went back down to 14. Is this normal? For a naturally aspirated car should I ever hit 17 or is that too lean? Like I said, it stays almost perfect at 14.5-15 if I don't drive it like I stole it.
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Old 06-22-2014, 05:29 PM   #10
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It sounds fine maybe a bit rich but it is ok there.
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