Thread: Formula to get air/fuel ratio?

Whats the formula to get from a reading you see in a cell on the fuel table? Also, i know it is not a representation of what we are running in that one cell of course.

I know Dave and John dont like to view the table in this manner and just use numbers but hopefully they will chime in on this formula. I once had it but lost my notes.

example: a fuel cell value of "57" equals a value of about 10.2:1

I don't know off hand but the free nistune basics of PDF had it in there.

http://www.plmsdevelopments.com/files/nissan_ecu_tuning_basics.pdf

see nistune doc.... i only remember it having the kvalue calcs though

nope. I check all 23 pages. None in there.

"Target A/F Ratio Multiplyer (M) AF Value Dec (D) AF Value in Hex
(AFR) M = 14.7 / AFR D = 128 x M - 128 (H)

Lean 15.9 0.924 182 B6
15.7 0.936 184 B8
15.5 0.948 185 B9
15.3 0.96 186 BA
Leaner 15.1 0.973 188 BC"
I found 2 from my research. 1 is above. The othe one is


"If the MAP VALUE is less than 128, then MULTIPLIER = (DATA + 128)/128
If the MAP VALUE is greater than 128, then MULTIPLIER = (DATA – 64)/128"
I don't know which one work.

The reason we don't use this formula is because it doesn't work and we don't want to be inundated with questions like these: www.ka-t.org :: View topic - why do i need 8s in my fuel map to get 11s?

Cheers,
Dave

BTW: There is no VE table in the stock B14 bin.

Here is the formula for anyone trying to convert thier fuel map to "estimated air fuel ratio"

If value is lower than 128
128/(X+128)*14.7

If value is greater than 128
128/(X-64)*14.7

where as "X" would be the old fuel map value (decimal not hex) ie: 30

I was totally confused about the tonnes of VE utterances in the thread.

Yep the formulas dont provide much detail regarding the various corrections due to enrichment etc.

Why dont you all just post the accurate formula though. We know you all know it

That's just it, since there is no accurate fuel map value to AFR formula, we don't know it. I can tell you that a closed loop fuel map value of 192 is equivalent to an open loop value of 0, in terms of change to IPW.

Dave

Until we can use widebands as our closed loop feedback, it is pointless to try to convert theoretical values that are heavily based on another multiplication factor to "target AFR's" that B14's use.

Target AFR's on the B14's are useless, they pretty much the same as OBD1's. 14.7 = 192, and the rest is just guess work...