T/A lt1

Is there a formula that corrolated milivolts to Air Fuel Ratio like. 14.7:1= 450mv. or 900mv=12.5:1. Something similar? LMK TIA Later Clint

americanmusscle

Might want to ask this question in the general f-body forum.

JasonD

Moved.

Injuneer

Its just about impossible to do..... the stock, narrow-band sensors are not intended to be accurate at anything other than 14.7:1 +/- 0.1 A/F ratio. As a result, a graph of senor output mV's vs lambda (A/F ratio referenced to stoichiometry) is almost a vertical line over the range of 14.8-14.6:1..... let's say for arguments sake that the range covers 200mv-700mV.

Then the curve flattens out to an almost horizontal line, where the range of (for example) 700-1000mV covers the extremes of 14.6 - 10.0:1. So, at the kind of A/F ratios you want to run for peak power and torque (12.8-13.2:1), a very large change in A/F ratio produces a relatively small change in mV output.

Add to this the fact that in the "rich" regime, the sensor is far more sensitive to operating temperature change than it is to A/F ratio change..... a moderate change in operating temperature can produced a larger change in mV output than a serious change in A/F ratio..... and a chart of mV output vs. A/F ratio for anything richer than 14:1 is not meaningful.

There is an article on O2 sensors in the latest issue of GM Hight-Tech Performance magazine, and they show a simple representation of the curve. In the past, I've extracted a much more carefully drawn curve from the Bosch Automotive Engineering Handbook, and taken the time to blow it up, divide it up into a grid, and do a table of the resulting mV vs. A/F ratio, and I could not correlate the resulting curve to the results produce in direct comparison to a wide-band sensor.

T/A lt1

Cool, I wasn't trying to tune with the o2 snesors just find out if I a way lean or way rich from tip in.

Injuneer

The stock LT1 tuning will typically set a target A/F ratio of 11.7:1 at WOT (PE mode). And I would guess that most people see O2 sensor values in the 910-930mV range for this condition. My car - back when it was a "bolt-on" setup - seemed to run better at around 880mV, which would indicate that it was getting a bit leaner.... maybe headed toward 12.8:1???. I've seen others like Keith at WS6.com indicate he got better results at 820mV.

I've also seen some scanners that seem to report lower O2 values than others for the same operating conditions.... the Hypertech "scan cartridge" for the HPP seemed to produce numbers 50-80mV lower than other scanners on the same level signals. Not sure what would explain that.

T/A lt1

Well i will be using a SnapOn scanner this afternoon to try and see if my car is going lean when I go to WOT from a dead stop since I installed my new cam and 58mm throttlebody. If it goes lean that will be where my bog is coming from and I can get a new program with more fuel. Thanks Later Clint