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Discussion Starter · #1 ·
I have a 2016 Focus ST and I have the Cobb AP set up showing my actual AFR, on idle it’s reading normal between 14.2-14.7 but once I start moving, different gears and rpms haven’t seemed to show any difference, it will consistently run 14.2-14.7, on occasion it will drop to 12.5 but from what I understand that’s still high. Typically 2k+ rpms if I am accelerating then take my foot off throttle wether I’m using the break or I’m engine breaking the APR shoots up to 43, I’m not sure if it’s normal to go that high on deceleration or not but it seems high to me. Any ideas on what could be causing this?
 

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I have a 2016 Focus ST and I have the Cobb AP set up showing my actual AFR, on idle it’s reading normal between 14.2-14.7 but once I start moving, different gears and rpms haven’t seemed to show any difference, it will consistently run 14.2-14.7, on occasion it will drop to 12.5 but from what I understand that’s still high. Typically 2k+ rpms if I am accelerating then take my foot off throttle wether I’m using the break or I’m engine breaking the APR shoots up to 43, I’m not sure if it’s normal to go that high on deceleration or not but it seems high to me. Any ideas on what could be causing this?
Thats all normal.

When in doubt, a quick google search will answer 98 percent of any questions.

Also, its an air to fuel ratio you are looking at. So the lower the number the richer it is. Rich is safe, lean kabooms.

Of course you see it go lean when decelling in gear, its not using any fuel. Thats where the fuel economy of a manual comes in.

The car will go rich under wot/boosted conditions, which is expected.

So your opinion of "high" afr is just normal operating conditions.

If you were experiencing any actual lean conditions the super thorough obd2 system would store a code about it.
 
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Like @Duece McCracken said above, the off the throttle numbers are normal. It should be close to stoich when at a constant speed on a level road. The time to really pay attention is when under boost when you need it to be richer.

If you take a log in 3rd or 4th, you should see the AFR dip down under boost.

Here is someones from one of the vdyno threads. The solid line on the lower part of the graph is the AFR, if you plot yours, it should look similar:
 

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Discussion Starter · #4 ·
I guess I had my information wrong. Thank you both of you for clearing this up for me! Appreciate it!
 
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