Hondata

Running a FlashPro on an 8th gen Civic Si (K20Z3) with a K&N Typhoon short ram intake (3”). I’ve hand-tuned the AFM flow table off fuel trims and it’s dialed when the intake’s cool — trims sit near zero around 75–90°F IAT. But when the IAT are 105-120 I’m getting +8%

The issue: as IAT climbs, my closed-loop trims climb with it, pretty linearly.
So on a hot or heat-soaked day (short ram, so it soaks), the ECU is adding a lot of fuel at cruise.

Here’s what’s confusing me: my WOT AFR barely changes between cold and hot logs — it’s ~12.1–12.5 flat either way, no knock in the meat of the pull. If the AFM were mis-reading air when hot, I’d expect WOT (open loop, no trims) to go lean by a similar margin. It doesn’t. Only closed loop shows the shift.

My questions:

1. Is this a known thing with a short ram / hot intake on these cars — trims climbing with IAT?
2. Should I be using the Air Temperature Fuel Compensation tables to correct it, or is the closed-loop trim doing its job and I should leave it? My air temp comp tables are currently all zeros.
3. Does the air temp fuel compensation table apply in open loop / WOT, or closed loop only? That’s the part I can’t confirm, and it matters — my WOT is already good, so I don’t want to add fuel there if the table affects it.

Post a log and the calibration and i can take a look at it. Normally for aftermarket intakes the cars run better in speed density. These car are known to heatsoak when you have an open air intake under the hood. The car may be doing what it needs to do to prevent knock. If you have zeroed out the temp tables then another table may be affecting fueling.

You car will increase fuel or reduce timing in order to reduce knock due to high intake temperatures.

-Ed