Does the winter weather have a factor on a motor running leaner than usual? I have an NA setup I was running at 13.9-14.3 AFR @ 70-80mph and now since it has gotten really cool my afr reads at 14.9 @ 70mph and sometimes jumps into the 15's as i go to higher rpms. Is this normal? Also, after what AFR would it considered to be unsafe to drive? I heard its okay for NA motors to go into the 15's AFR.

 

your cruising, i would be happier with mid 15's AFR, but my ECU jumps between 14.7 and 15.1 or so. cruising i bet u could push the engine into the 16's with no ill effects since theres very low load on it.

cold weather= denser air=leaner AFR
i just had to retune mine yesterday as well the AFR was well into the 15's and brough it back to mid-low 14's

 

I don't think I'll try pushing it to 16's to be on the safe side. I thought low 15's was already bad. Anyone drives in mid 15's daily? If anyone can verify mid 15's is perfectly safe, I think ill try to get my AFR at mid 15's for better gas mileage.

 

mid 15's is a tad lean but if your cruising with out much load on the engine it wont hurt anything. When your cruising at 70, if u lay on the gas does it detonate for a little bit? If not i wouldnt worry about it.

like he said, colder air is more dense.

 

If you have your closed loop disabled, then it won't hurt to target higher a/f values in the first 3 columns or low vacuum table range. If you still have your closed loop enabled, it won't make that much of the difference since the ecu will monitor your O2 sensor and try to compensate. I would also be cautious and think twice about running higher a/f values if you aren't an experienced tuner and/or your engine setup is running a very aggressive setup(cams, high compression, aggressive ignition map, agressively tuned cam gears, etc)

My $.02

 

i believe that fuel in the winter have different additives in them that might cause it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ericrx_88 &raquo;</TD></TR><TR><TD CLASS="quote">i believe that fuel in the winter have different additives in them that might cause it.</TD></TR></TABLE>

Certain snow states get winterblend fuel which can cause havoc on an agressively tuned map like the one I was running. For winter, I had to tone down my ignition maps and slightly increase my low fuel map.

 

remember, cold air is more dense