Holley COMMANDER 950 - Manual (Page 35)

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To tune WOT, find a safe place where the vehicle can be accelerated to legal speeds. Again, you need one person driving
and one person tuning and monitoring. Open the main fuel map. The sensor that needs to be monitored carefully is the
oxygen sensor voltage output. This is found on the data monitor (O
2
V). This voltage is also shown in large numbers on
the Rich/Lean indicator. When this voltage is below .45 volts, the color will be red. When this voltage is between .45 and
.75 volts, it will be yellow. When the voltage is above .75 volts, it will be green.
Figure 17 Fuel Map Showing Proper Wide-Open Throttle O
2
Voltage
NOTE: You will know you are open loop when the O
2
mod is fixed on 100.
Gradually open the throttle fully and watch the O
2
voltage and note the color of the Rich/Lean indicator. Once the engine
goes open loop this voltage should be at least .75-.8 volts and the indicator should turn and stay green. See Appendix 7
on voltage sensor output information. If this voltage is less than .75-.8V then you should immediately add more fuel to
the lean areas. As the vehicle hits wide-open throttle, note the rpm at which the engine is lean. Make changes and test
again. Once again, the fuel map should be smooth. Keep checking for this on the fuel graph. Once the voltage is proper
through the entire rpm range at WOT the entire base fuel map should be tuned fairly well. The picture above shows a
WOT O
2
voltage of .75 volts. If the voltage is higher than .8, such as .9, it does not necessarily mean that the A/F ratio is
too rich. Every application and engine is a little different so be careful.
As is discussed in Appendix 6, in isolated cases, some vehicles may NOT exhibit higher voltage readings even when the
A/F ratio is in a safe region. If you have any questions call for technical support.
After you get the base fuel map very close, the engine should run fairly well if all the other parameters from the base map
are reasonably close for you application. Getting the base map very close is the most important part of tuning EFI.
If it is not close in areas, you will not be able to compensate for the problems it will cause. Do not proceed to the next
section until you are sure the base map is correct. The only performance that may not be close is cold start performance.
This will be covered in the next section. Once the base map is tuned, NEVER modify it to compensate for poor cold
engine operation.