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View Full Version : Tuning: Wide Band O2 Sensors - and Water/Methonol Injection

car_habbit
25-11-2004, 07:06 PM
Is there a table or formula to correct the indicated Air Fuel ratio from a wide band oxygen sensor as a function amount (% of fuel) Methonol mix injected and the Water/Methonol mix percentages?

This is a CRITICAL issue for both dyno tuning with WBO2 and for Wide Band closed loop fuel injection systems:

If I have a car that will not run at full throttle without detonation, I need to do even the initial tuning with the water injection on. Wide band O2 sensor readings will obviously change with the water/methonol injection, so it is necessary to correct the indicated reading. In this case, the user does not have the typically suggested luxury of running without WI to set the fuel before adding WI.

Is there a table or formula that can be used to correct the indicated readings to get reasonably accurate corrected readings?
hotrod
25-11-2004, 08:13 PM
You should switch the wideband so that is shows the fuel air mixture as lambda values. That should account for the contribution of the methanol.

http://www.techedge.com.au/vehicle/wbo2/wblambda.htm

Larry
RICE RACING
26-11-2005, 01:57 PM
The *actual* number is not important, by simply adding meth to the mixture in various quantities all you will do is alter your running AFR.

SO if you always aimed for 11.7:1 on WOT and max rpm then you will aim for this SAME number with the meth/petrol mixture, just as you would if you were running 100% meth, its no different.

Think about it for a minute and you will understand the logic of it ;)

The *correct* number has no relevance except for when you wanted to calculate back another figure from the correct AFR balance for that fuel type or fuel mixture ratio blend.

This is applied in Autronic ECU's for example, there is only a target AFR table based of petrol stociometric scale (14.7:1) and all the numbers that follow to make sence regardless of what fuel type your running. Just as Lambda is a number so too is Petrol AFR and its values, your targets will never change regardless of what mixture or blend you run :idea: