5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

Air to fuel ration

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Old 06-23-2014, 08:38 AM
  #11  
88 orangepeel notch
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At WOT, does it stay at 11.3 the whole time? As stated above, at initial wot, mine may drop to 11.5 - 11.8, but then quickly recover and hold 12.8-12.9 the whole pull.

Everything else about your setup sounds right.
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Old 06-23-2014, 10:16 AM
  #12  
yurizx6r
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My lowest reading was 11.3 with the "race" tune. I still need to do more pulls with the car and stick with a tune. Once I take my foot of the gas it will go up to 17 and then go back down to 14.5-15. I was wondering if that was normal or too lean. From what I am gathering, it seems 11.3 is a little too rich since it's a naturally aspirated car. I was also told that if it goes to 17 after a pull not to worry as long as it goes back down because the fuel injectors shut off temporary until it stables out at idle. What I am going to do is put it back on the regular (close to stock) tune, drive it for a few miles, and then gather what it's doing. The regular tune runs smooth, the "performance" tune runs a little rougher, and the "race" tune I can smell gas.

I also found this, "
A/F Characteristics
Ratio
5 Rich burn limit. Combustion is weak and/or erratic.
6-9 Extremely rich. Black smoke and low power.
10-11 Very rich. Some supercharged engines run in this range at full power as
a means of controlling detonation.
12-13 Rich. Best power A/F for normally aspirated WOT.
14-15 Chemically ideal. At 14.6 the A/F is at the theoretical ideal ratio
with no excess fuel or oxygen after combustion. Good A/F target for part
throttle cruise and light to moderate acceleration.
16-17 Lean. Best fuel economy A/F ratio. Borderline for part throttle
drivability (worse than borderline if EGR is used).
18-19 Very lean. Usual lean limit (Driveability).
20-25 Lean burn limit. Varies with engine."

Would this be a good table to go by?
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Old 06-23-2014, 01:05 PM
  #13  
88 orangepeel notch
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Yeah, that description of A/F ratios is what I've always gone by.

And your plan for your car sounds good. Let the computer relearn parameters and then start tinkering with a tune. Remember though………baby steps lol.
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Old 06-23-2014, 01:25 PM
  #14  
yurizx6r
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Yeah you're right. This is my first experience with an air/fuel gauge, so I didn't know what to expect. I decided to buy it because I just put in pretty much every bolt on you can do besides heads and forced induction with the stock injectors, so I wanted to see if the car was running too lean or anything like that. Besides, it's a great tuning tool to have for the future. I will do a few more pulls and see what results I get, but now I know what to look for at least.
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Old 07-11-2014, 07:43 AM
  #15  
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Ok, so after some setbacks and life events I finally got a chance to drive it and do some more pulls. I put it back to the "stock" tune over the very rich running "race" tune. During WOT it usually goes down to 13.3, but the lowest I saw was 12.6. As soon as I take my foot of the gas it will go to 17, but stabilize between 14.5-15.2. If I drive it normally, it stays between 14.5-15.2 also. I am guessing this is chemically ideal, and I shouldn't have to touch it?
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Old 07-12-2014, 06:48 AM
  #16  
88 orangepeel notch
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Yep, thats a good setup. Maybe alittle lean at WOT, but since your na, I wouldn't change a thing.
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Old 07-15-2014, 06:49 AM
  #17  
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Sweeeet. Looks like I've got this figured out then. Thanks!
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Old 07-17-2014, 03:58 PM
  #18  
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13.0 is pretty good for an N/A car. I recently was having issues not mphing like the car should for making 1300 hp on motor, bought a set of 02 sensors for my racepak, we were getting 14.1 going down track. Made a 7 jet up switch to add a lot more fuel (Q16) dropped the air fuel down to 11.9-12.1 going down track, car sounded horrible in the burn out but picked up 2 mph. I went back 3 jet sizes and got the Air fuel to read around 12.5 to 12.7 and it picked up another .5. Just give the car what it wants, every engine will want different amounts of fuel.
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