Checking A/F ratio with predator
5/31/06, 09:05 AM
#1
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Checking A/F ratio with predator
I know its been talked about on here before, but I searched and couldn't find the answer. What parameters do you data log to check your A/F ratio with the Predator. If I remember correctly the readout is in volts but I thought someone knew what the conversion was or what volts were acceptable. Also do you have to do it WOT or can it be done under normal driving conditions. TIA
5/31/06, 09:52 AM
#2
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You can't. And it has NOTHING to with the Predator. The S197 has four NARROW band O2 sensors and NO wideband O2 sensors.
What does this mean? It means the only thing the computer really knows is if it is on the rich (no O2 present) side of stociometric (that 14.7:1 for gasoline) or on the lean side (excess O2 present). The response curve of a narrowband O2 sensor is so nonlinear that it can ONLY tell you "rich" or "lean".
Heck, the cars closed loop control algorythms use this. When you are cruising down the road in closed loop and the ECU detects a "rich" condition, it will slowly lean out the mixture bit by bit until the signal switchs to a "lean" condition. Then it starts richening it up bit by bit until it switchs again. It will continue to do this the whole time it is in closed loop. It doesn't say "set mixture for 14.7:1 and hold it". Because it can't.
If you want to use the Predator (or an SCT XCal) to read A/F ratio, you have to install a wideband O2 sensor AND the controller. There are several different versions out there these days and the price is pretty reasonable. Innovative Motor Sports has their LC-1 that runs right at $200 with the O2 sensor (if my memory is correct). This system can be interfaced into the analog inputs to the Predator (I think) or the X-Cal 2 (I Know) to read a true A/F ratio.
What does this mean? It means the only thing the computer really knows is if it is on the rich (no O2 present) side of stociometric (that 14.7:1 for gasoline) or on the lean side (excess O2 present). The response curve of a narrowband O2 sensor is so nonlinear that it can ONLY tell you "rich" or "lean".
Heck, the cars closed loop control algorythms use this. When you are cruising down the road in closed loop and the ECU detects a "rich" condition, it will slowly lean out the mixture bit by bit until the signal switchs to a "lean" condition. Then it starts richening it up bit by bit until it switchs again. It will continue to do this the whole time it is in closed loop. It doesn't say "set mixture for 14.7:1 and hold it". Because it can't.
If you want to use the Predator (or an SCT XCal) to read A/F ratio, you have to install a wideband O2 sensor AND the controller. There are several different versions out there these days and the price is pretty reasonable. Innovative Motor Sports has their LC-1 that runs right at $200 with the O2 sensor (if my memory is correct). This system can be interfaced into the analog inputs to the Predator (I think) or the X-Cal 2 (I Know) to read a true A/F ratio.
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