Ok. I'm close to getting my part throttle fuel straightened out except for a lean condition during very slow speed like creeping along in a parking lot at about 20-25 gms/sec airflow. I can't figure that one out because if I add more fuel the block learn drops. It's just a very short period of leaness and then it recovers. The car is a 6 speed so it sputters and bucks.

Anyway, my question really pertains to WOT tuning PE vs RPM. I understand how it works and what it does. I am going to a local dynojet and will be using their wide band O2 for my pulls. I'm not sure if the wide band displays air fuel ratio or just milivolts. What is the optimim AF ratio for WOT? Does it vary throughout the RPM scale? If say at 4500 my O2 volts show lean at 850. I want them at say 920. I look at my PE vs RPM table and see the value for that RPM is
-5. How much fuel do you add to get to 920? I have a feeling the answer is a crap shoot. Am I right?

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89 Vette 6 speed
CNC heads, crane cam, Miniram, headers
Soon to be 396 Small Block!

 

If you're just cruising around a parking lot and you're running lean in that airflow range, you need to change the MAF tables. There is a past topic that covers this, probably with MAF in the title. You bump up the airflow values to add more fuel at that Count #, since the Count # corresponds to a certain amount of fuel added. Since this airflow range straddles the end of the 1st MAF table and the beginning of the 2nd table, you might want to check that the last value from the 1st table is the same or slightly lower than the first value from the 2nd table. I had that same problem, plus some leaness at idle, and correcting those 2 things took care of it.

I'm not sure what value you should shoot for with a wideband O2 sensor; hopefully they'll have some way of converting it to A/F ratio. Yes, it's a crap shoot trying to guess how much a change in fuel affects the O2 voltage.

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Greg Westphal
'87 IROC 305TPI/A4

 

You tune for HP not a specific AFR or for an O2 sensor reading. You want the richest AFR that makes the most power. This AFR is different for every engine. N/A engines may make best rich power around 12.5-13.0.

 

Cool. Thanks.

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89 Six Speed FX3 coupe
More Performance 396cid specs:
Callies 4340 crank 3.875 stroke
Lunati Pro-Mod 5.85" rods
SRP Pistons 14cc dish
Comp Cams Custom cam 550 lift 220/229 duration
10.8:1 compression
AFR 195 competition ported heads
Miniram and TPIS 1 3/4" headers

 

What would the voltages be to try and tune the AFR using the crappy stock O2 sensor?

Couldn't you just shoot for a leaner AFR voltage at WOT?
You'd be able to see the redzone by knock counts, right?