does ambient temp/IAT effect A/F ratio? LOGS posted.

**lrg8683** · 09-21-2008 12:53 AM

i was out doing some logging/tweaking after installing a new FMIC and new spark plugs (bkr7e - .028) anywho, before with my old fmic and old plugs i had my A/F right around .86-.87 ..after new fmic and plugs and no lemmi changes the a/f was around.89-.90 .. granted when i did my logging with my old setup it was about 73-75 degrees out.. tonight it was 64-66 degrees out.. any help is appreciated.. ill post up some of th graphs in a little while

**Triple8Sol** · 09-21-2008 08:19 AM

Absolutely. Air temp, humidity, altitude....all those things will effect the density of the air, thus effecting your A/F ratio.

**BITRBO** · 09-21-2008 08:37 AM

nice graphs man! did you do those with VAGCOM or APR's "ECU-x"?

But to answer your question: yes. the cooler the air, the more dense it is, which affects the a/f ratio slightly. But only to an extent, as the ECU should automatically adjust the fuel content based on the amount of air coming it. This is calculated based on the data received from the various sensors (i.e. IAT, O2, EGT, etc.).