More of an engine question, but still quasi-tbi related since alot of us use highway mode whether we know it or not. What is the safe lower limit on AFR's at part throttle cruising? During highway operation, the ecm enters its highway mode and the 02's drop to almost nill. Just maybe 3 or 4 millivolts of return. Is it safe to run the motor this lean in cruise? I know around .1 volt is around 17:1 but it looks like im off the low end of the scale. What are the safe lower limits on fueling before my pistons are reduced to eight 4in. diameter blobs?

 

As far as i know, detonation is what destroys pistons. A lean tune is just fine so long as its not lean enough to cause lean misfire and your spark tables are tuned accordingly

 

i have my hi-way mode set ot about 17.4:1, i have no detination issues.

what exactly are you o2 readings? i think i was your post on the diy board. IIRC .04mv is clean air for the o2 sensor.

 

my 02s (stock, not WB) are .004V. As a ballpark estimate, what should they be? Around ..07-.1 volt?

 

i'd have plug in the laptop and get out on the hiway to check my o2 voltage once hi-way mode has come on. might be able to do that this weekend for you.

 

do you happen to know what stock is? roughly i mean.. i realize it'll proby vari a little....


and how low can you go?

 

haven't tried to see how low i can go.

depending on vacume it varied from like 15.6-17.1 stock. i bascily added 3thenth of a point across the board. it has worked fine. i really need to do some long term fuel millage testing, to see exactly what AFR the best millage can found at when using the HW mode.

 

JPrevost was nice enough to search my bin for my ecm and found the tables in a different spot. Assuming i set the addl. table up right in tuner cats tdf file, the AFRs are around 15.1:1 or so in my ecm and teh VE table is pretty close. What bothers me is that the fueling looks like its alot farther off then what the ecm is commanding. Maybe its those unkown pph holley injectors i have.