Im new to using a wideband lm-1 meter and i found this chart online. Im trying to figure if the reading im getting from my car are correct. Are the reading in the chart below good to use as guide lines????

Cold Start (first 30 sec)
11.5-12.5 AFR

Idle
12.8-13.5 AFR

Part Throttle Cruise
13.0-14.0 AFR

Wide Open Throttle
12.5-12.8 (values down to 11.5 may be used to reduce detonation) AFR
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Those don't even look to be good for a rough "ballpark" start to your tune. You tune it on the dyno, maximizing performance, and then note the A/F ratio that achieved that maximum performance. There is no "one size fits all" for tuning the A/F ratio..... each engine is different. Even after the dyno tuning, you will still want to tweek things under actual driving conditions.... particularly at the track, and the wide-band will help you do that.

The idle and part load programming in the PCM is hard coded to 14.7:1. I'm not sure why you would want it to idle at 12.8-13.5:1..... that would just be wasting fuel. You could actually get better fuel milage running a bit leaner than 14.7:1, but they picked 14.7:1 for factory programming because that is the A/F ratio that produces the lowest combined total emissions of CO, HC and NOx. Any richer, and CO and HC emissions increase, any leaner and NOx increases. The cat(s) are designed to function correctly when the engine is running at 14.7:1. Similarly, not sure why you would want to cruise any richer than 14.7:1, since that normally will produce good streetability and good fuel milage. All that assumes a "stockish" cam.... when you get into high overlapp cams, there are no "rules" for A/F ratio, because the exhaust is so heavilly affected by the fuel blowthrough during overlap.

For WOT operation, the old rule of thumb was 12.8 - 13.2:1 for peak power and torque. But again... that's just a starting point. Each engine is different. We do know that the factory programming produces a typical WOT target A/F ratio of about 11.7:1, and its too rich. You can pick up a quick 10-12HP simply by leaning out the PE mode target A/F ratio.

Are you running a stock PCM or using an aftermarket ECU? An aftermarket unit would allow you to play with the closed loop part load and idle tuning. And there are ways around the stock PCM to alter the idle and part load tune.

 

im using a stock pcm with madz28s tuning. but im trying to get all the infomation i can because of future tunercat purchases. thanxs for the your
info.I found that chart online thats not what my reading really are. to me the chart looks alot like what you would see tuning a carb app.