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Recently installed a JB4 everything seems to be running smoothly besides AFR spikes when I let off the gas. My first thought would be that it spikes due to less fuel but I figured I would post here to see if anyone had any insight. New to the JB4 and tuning in general. If anyone has any information at all a comment would be greatly appreciated!!
1927B6C4-BE6A-47DF-B7D8-70B8FE4BBD38.png

(Map 1)
 

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2015 auto VT, 2013 manual VT × 2
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It's called DFCO or Deceleration Fuel Cut Off which is normal and part of every oem tune.
 
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2015 auto VT, 2013 manual VT × 2
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2016 Veloster Turbo DCT w/ Tech Package
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It's called DFCO or Deceleration Fuel Cut Off which is normal and part of every oem tune.
Yep. If you would have connected an AF gauge even before connecting the JB4 you would have observed the same behavior. Since you are new to the JB4 I would recommend driving around on Map 0 for a while and doing some logging and watching the gauges so you can see what everything is like before you start trying the maps. I have been running a JB4 on my 2016VT since Nov 2020 and have had some ups and downs. Mostly the trouble I have encountered has been from ambitious experimentation. I have a thread on here with some of my observations and experiences listed. One thing to keep in mind is that if you end up throwing codes they aren't always going to be precisely accurate for the problem. Since a piggyback tuner is doing things the ECU doesn't really know about/expect, a CEL code will be what the ECU thinks the problem is but it may be something quite different since the JB4 is changing some things. Currently I have a custom intake and a few structural mods to pull heat from the engine bay as well as some weight reduction and I am running a customized Map 6 and 15% Ethanol pump gas. One of these days I will get to a dyno or strip to have a sheet to show how well it's performing.
 
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