Help me understand..(scanmaster and tuning)
01-18-2002, 07:14 PM
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Help me understand..(scanmaster and tuning) Well i picked up a scanmaster now that i have a cam and headders I was thinking i might want to tune my setup. I,ve done some serching on what the 02's should read and the L-trims. Just a little confusion. (probly stupid question)
Ok the 02 readings bounce around ALOT. Figure its normal since its not wideband? And when they are doing this what would i look for? I read you should look for o2's to be ABOUT .890 on normal driving THEN look for L-trims to be round 00 at WOT? Is this Correct? I know i Need MAFT to adjust it. Just wanting to know what to look for first.
But if the 02's are ustable how do i know if they are at .890 during normal driving?
Ok this is what i can understand so far. 02's recordings are around .896-.920 Mostly .890 range under WOT readings. (if i gass it the 02's stop bouncing around)Also 00 kr so far.
But what im worried about is when i drive normal (easy) the L-trims will be about 8-16? Does this mean im Lean? When i gas it they will level out about 4-6 L-t(2) will always be about 2% less then l-t(1)??
Sorry for the questions you can probly tell im clueless.lol All the other readings i can understand (if needed) Like Injector pulse?? Dont think i relly need to know that now?? Right? Ok ill quit pestering. Any help would be thankful...
Thanks!!! Tim 98z <img src="graemlins/gr_hail.gif" border="0" alt="[hail]" />
Ok the 02 readings bounce around ALOT. Figure its normal since its not wideband? And when they are doing this what would i look for? I read you should look for o2's to be ABOUT .890 on normal driving THEN look for L-trims to be round 00 at WOT? Is this Correct? I know i Need MAFT to adjust it. Just wanting to know what to look for first.
But if the 02's are ustable how do i know if they are at .890 during normal driving?
Ok this is what i can understand so far. 02's recordings are around .896-.920 Mostly .890 range under WOT readings. (if i gass it the 02's stop bouncing around)Also 00 kr so far.
But what im worried about is when i drive normal (easy) the L-trims will be about 8-16? Does this mean im Lean? When i gas it they will level out about 4-6 L-t(2) will always be about 2% less then l-t(1)??
Sorry for the questions you can probly tell im clueless.lol All the other readings i can understand (if needed) Like Injector pulse?? Dont think i relly need to know that now?? Right? Ok ill quit pestering. Any help would be thankful...
Thanks!!! Tim 98z <img src="graemlins/gr_hail.gif" border="0" alt="[hail]" />
01-19-2002, 01:50 AM
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Re: Help me understand..(scanmaster and tuning) Hi Tim,
The O2 readings obtained from the standard O2 sensors should bounce around when operating correctly. It works like this (well it did last time I looked):
The O2 sensors (cheap and nasty) can only detect rich or lean and then only if the afr is close to stoich (i.e. when the afr is around 14.7). That means your PCM is only supplied with minimal information from your O2 sensors. Lean or Rich - that's it. So the voltage reading is going to swing quickly from low to high - as the PCM "discovers and learns" that the combustion is rich or lean and compensates accordingly.
The longer the O2 sensor stays above or below the "stoich line" - 14.7 then the PCM determines that the combustion is lean or rich respectively.
The faster it crosses over the stoich line the closer the PCM determines the combustion is at stoich.
The fact that the O2 sensor voltage levels out at WOT is that the PCM enters "open loop" above about 70% throttle. Open loop is when the PCM ignores the O2 and calculates the injector pulse widths directly from the calibration maps in your PCM. Most calibrations will run the AFR rich at WOT. So at WOT you will see the O2 sensor screaming "hey its rich and it's been rich for a long time" (i.e. I haven't crossed over stoich recently). But the PCM is ignoring it - and running open loop.
Hope that helps.
Disclaimer: IANAEFIT (I Am Not An EFI Technician) anything that I have said has been learnt hacking software on ALDL and OBD-II systems.
The O2 readings obtained from the standard O2 sensors should bounce around when operating correctly. It works like this (well it did last time I looked):
The O2 sensors (cheap and nasty) can only detect rich or lean and then only if the afr is close to stoich (i.e. when the afr is around 14.7). That means your PCM is only supplied with minimal information from your O2 sensors. Lean or Rich - that's it. So the voltage reading is going to swing quickly from low to high - as the PCM "discovers and learns" that the combustion is rich or lean and compensates accordingly.
The longer the O2 sensor stays above or below the "stoich line" - 14.7 then the PCM determines that the combustion is lean or rich respectively.
The faster it crosses over the stoich line the closer the PCM determines the combustion is at stoich.
The fact that the O2 sensor voltage levels out at WOT is that the PCM enters "open loop" above about 70% throttle. Open loop is when the PCM ignores the O2 and calculates the injector pulse widths directly from the calibration maps in your PCM. Most calibrations will run the AFR rich at WOT. So at WOT you will see the O2 sensor screaming "hey its rich and it's been rich for a long time" (i.e. I haven't crossed over stoich recently). But the PCM is ignoring it - and running open loop.
Hope that helps.
Disclaimer: IANAEFIT (I Am Not An EFI Technician) anything that I have said has been learnt hacking software on ALDL and OBD-II systems.
