AFR and Vacuum numbers

[Deleted member 63295]

Just curious of what numbers the gauge read on your mustang at idle for AFR and Vacuum?

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[Alan Applegate]

I've only looked a couple of times. The fuel ratio is strictly based on how hard you push the go pedal. The vacuum reading is about right once the engine is warm. Cold, 10 Hg is average. On deceleration, 20 is closer depending on the altitude, temp., etc.

If you're driving an Eco-Boost, what you see peak boost wise, depends on which mode you're in. In drag mode (which is highest) you can get to 24 and a faction, but not for very long. Other modes, is's about 22 pounds peak.

 

[RLE55]

https://www.safrtool.com/SAFR-AFR-values.asp

 

[Ryunker]

In my DH it is almost always 13.5 to 13.7. Really wish it would be more like 14.5

 

[robvas]

In my DH it is almost always 13.5 to 13.7. Really wish it would be more like 14.5

Why?

Also what do you mean by 'almost always'? Cruise, idle, WOT, decel, all going to be different

 

[SSuperDave]

14.7 is the ideal stoichiometric #, but it will fluctuate on acceleration, as does vacuum. Vacuum goes up on coast and down on accel.

 

[Deleted member 63295]

Thanks guys

 

[robvas]

14.7 is the ideal stoichiometric #, but it will fluctuate on acceleration, as does vacuum. Vacuum goes up on coast and down on accel.

These days gasoline is all E10 so the computer is actually going to target something like 14.1

And that goes along with timing so you rarely see that exact value (which isn't always targeted anyway). And the OEM is going to be doing things for power/fuel economy.

 

[drive_55_not]

14.7 is the ideal stoichiometric #, but it will fluctuate on acceleration, as does vacuum. Vacuum goes up on coast and down on accel.

Ford is using E10 stoich 14.08 as the reference for the AFR reading, So 13.9 - 14.1 at idle, cruising and part throttle is normal.


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[Ryunker]

In my DH it is almost always 13.5 to 13.7. Really wish it would be more

Why?

Also what do you mean by 'almost always'? Cruise, idle, WOT, decel, all going to be different

gas mileage, 14.7:1 is the goal, 13.5 to 13.7 unless crazy driving AFR is there 90% of the time. If I could I would lean it out a bit.

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