Should L-Term readings be done at idle or cruise?
08-06-2002, 08:24 PM
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Should L-Term readings be done at idle or cruise? Everyone says they should be at 0 or slightly negative.
Is this measurement to be taken from idle or cruising at part throttle?
Thank you!
Is this measurement to be taken from idle or cruising at part throttle?
Thank you!
08-07-2002, 02:41 PM
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Re: Should L-Term readings be done at idle or cruise? Ltrims at WOT are useless. You're in open loop at WOT.
I've tuned them in at idle then fine tuned at part throttle and I've tuned them in using only part throttle. If you're tuning in A/F, get your ltrims between 0 and -1.8% and then start tuning in your WOT A/F. Most times you are pretty damn close at WOT if your part throttle ltrims are correct.
I've tuned them in at idle then fine tuned at part throttle and I've tuned them in using only part throttle. If you're tuning in A/F, get your ltrims between 0 and -1.8% and then start tuning in your WOT A/F. Most times you are pretty damn close at WOT if your part throttle ltrims are correct.
08-07-2002, 02:52 PM
#6
Re: Should L-Term readings be done at idle or cruise? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by TrentSS:
<strong>I never count L-trims at part throttle. I only measure L-trims at idle and WOT only. Part throttle is useless IMO.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is opposite what you want to do when monitoring LTFTs.
Only monitor at part throttle conditions.
<strong>I never count L-trims at part throttle. I only measure L-trims at idle and WOT only. Part throttle is useless IMO.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is opposite what you want to do when monitoring LTFTs.
Only monitor at part throttle conditions.
08-07-2002, 03:39 PM
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Re: Should L-Term readings be done at idle or cruise? Okay guys...before an old man gets beat up on this site, I meant to say I only monitor L-trims at idle.
I don't monitor L-trims at WOT. The only thing I concern myself with at WOT are O2's on both banks, timing, and knock retard.
Why monitor L-trims at part throttle, especially if one uses an MAFT to adjust their A/F ratio? You simply have a Base setting and a WOT setting. Monitoring part throttle means virtually nothing IMO.
I don't monitor L-trims at WOT. The only thing I concern myself with at WOT are O2's on both banks, timing, and knock retard.
Why monitor L-trims at part throttle, especially if one uses an MAFT to adjust their A/F ratio? You simply have a Base setting and a WOT setting. Monitoring part throttle means virtually nothing IMO.
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08-07-2002, 03:53 PM
#8
Re: Should L-Term readings be done at idle or cruise? I only monitored LTrims as a baseline, and played with the MAF-T dials until my LTrims (at idle and 3/4 throttle) were close to 0 (err on the positive side). I'd keep tweaking the dials until I had the timing and O2 readings (between .890-.900) that I was looking for at WOT and LTrims near 0. Don't touch the WOT dial until you get the LTrims set how you want them first.
Tony
<small>[ August 07, 2002, 03:55 PM: Message edited by: Nine Ball ]</small>
Tony
<small>[ August 07, 2002, 03:55 PM: Message edited by: Nine Ball ]</small>
08-07-2002, 04:10 PM
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Re: Should L-Term readings be done at idle or cruise? Powertrain is not in open loop during WOT, GM has a special mode for WOT that ignores 02s but all the other functions of closed loop are still used.
Those with Ease scanner, Just click on IM from a cold start, you will see open loop, once to temp goes to closed loop and stays there in in PE.
Open loop would run AIR and turn voltage on for 02 resistors which you would not want once engine is up to temps, esp at PE (WOT).
Also a OBD-II PID you could scan that tells you when in open or closed loop so scan and review esp during PE.
Trim cells do have an impact to PE for PE multiplies a value to what trims were like at the time PE is triggered and reason why you could be rich trims during PT but lean during PE because if trims are rich, PCM is going leaner and PE only adds a scaled multipler value to that so if trim is -10, PCM is going +10, so PE is biased lean and only uses the value for the RPM and engine time at that time.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by DenzSS:
<strong>Ltrims at WOT are useless. You're in open loop at WOT.
I've tuned them in at idle then fine tuned at part throttle and I've tuned them in using only part throttle. If you're tuning in A/F, get your ltrims between 0 and -1.8% and then start tuning in your WOT A/F. Most times you are pretty damn close at WOT if your part throttle ltrims are correct.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">
Those with Ease scanner, Just click on IM from a cold start, you will see open loop, once to temp goes to closed loop and stays there in in PE.
Open loop would run AIR and turn voltage on for 02 resistors which you would not want once engine is up to temps, esp at PE (WOT).
Also a OBD-II PID you could scan that tells you when in open or closed loop so scan and review esp during PE.
Trim cells do have an impact to PE for PE multiplies a value to what trims were like at the time PE is triggered and reason why you could be rich trims during PT but lean during PE because if trims are rich, PCM is going leaner and PE only adds a scaled multipler value to that so if trim is -10, PCM is going +10, so PE is biased lean and only uses the value for the RPM and engine time at that time.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by DenzSS:
<strong>Ltrims at WOT are useless. You're in open loop at WOT.
I've tuned them in at idle then fine tuned at part throttle and I've tuned them in using only part throttle. If you're tuning in A/F, get your ltrims between 0 and -1.8% and then start tuning in your WOT A/F. Most times you are pretty damn close at WOT if your part throttle ltrims are correct.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">
08-07-2002, 07:54 PM
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Re: Should L-Term readings be done at idle or cruise? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Team ZR-1:
<strong>Trim cells do have an impact to PE for PE multiplies a value to what trims were like at the time PE is triggered</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Are you sure that the WOT Power Enrichment uses information from the Trim Cells? What makes you think so? Some people say that the LTFT cells are used as a multiplier when going to WOT P.E., others say that the LTFT cells are not used.
If the LTFT cells are used when going to WOT PE, which cells are used? Don't forget that we have 0 - 22 trim cells.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Team ZR-1:
<strong> and reason why you could be rich trims during PT but lean during PE because if trims are rich, PCM is going leaner and PE only adds a scaled multipler value to that so if trim is -10, PCM is going +10, so PE is biased lean and only uses the value for the RPM and engine time at that time.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Huh? I do not understand this statement at all.
If we have rich trim during PT, the LTFT values are negative and the PCM is removing fuel. I am ok with that. I have no idea what you are saying here:
>>PE only adds a scaled multipler
>>value to that so if trim is -10,
>>PCM is going +10, so PE is biased
>>lean and only uses the value for
>>the RPM and engine time at that time
If trim is -10, PCM is going +10???? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
<strong>Trim cells do have an impact to PE for PE multiplies a value to what trims were like at the time PE is triggered</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Are you sure that the WOT Power Enrichment uses information from the Trim Cells? What makes you think so? Some people say that the LTFT cells are used as a multiplier when going to WOT P.E., others say that the LTFT cells are not used.
If the LTFT cells are used when going to WOT PE, which cells are used? Don't forget that we have 0 - 22 trim cells.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Team ZR-1:
<strong> and reason why you could be rich trims during PT but lean during PE because if trims are rich, PCM is going leaner and PE only adds a scaled multipler value to that so if trim is -10, PCM is going +10, so PE is biased lean and only uses the value for the RPM and engine time at that time.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Huh? I do not understand this statement at all.
If we have rich trim during PT, the LTFT values are negative and the PCM is removing fuel. I am ok with that. I have no idea what you are saying here:
>>PE only adds a scaled multipler
>>value to that so if trim is -10,
>>PCM is going +10, so PE is biased
>>lean and only uses the value for
>>the RPM and engine time at that time
If trim is -10, PCM is going +10???? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
08-07-2002, 10:37 PM
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Re: Should L-Term readings be done at idle or cruise? Are you sure that the WOT Power Enrichment uses information from the Trim Cells? What makes you think so? Some people say that the LTFT cells are used as a multiplier when going to WOT P.E., others say that the LTFT cells are not used.
at the point of going PE, PCM looks at STFT value, then freezes them, it then attempts to zero LTFT to zero.
PE table's value is then mulitplied to what the trim value was at the point of freezing.
If the LTFT cells are used when going to WOT PE, which cells are used? Don't forget that we have 0 - 22 trim cells.
Let's not confuse fuel trims with fuel cells.
I assume your using LS1esit, look at PE temp, RPM, max multipler, hot and cold sections, they dicate when PE pccurs along then with TPS.
What cells are used would depend on if the conditions of the above are met but consider cells below 6 are low MAF freq usage and when lifting g-pedal. Take MAF max freq ( 12 to 13000 Hz) and divide that by the 23 cells, now you know the freq window eash cell uses.
I consider cells at the least 15 and 22 PE and could be as low as 14, it depends on how much load ( how big a pump the engine is sucking air volume, the higher the MAF freq is and thus clearly cell 10 would be like doing 70 MPH in 6th gear but if you dropped to 5th gear, also doinjg 70 it would go to cell 11 for engine is pumping more air in since RPM is higher.
Originally posted by Team ZR-1:
and reason why you could be rich trims during PT but lean during PE because if trims are rich, PCM is going leaner and PE only adds a scaled multipler value to that so if trim is -10, PCM is going +10, so PE is biased lean and only uses the value for the RPM and engine time at that time.
Huh? I do not understand this statement at all.
fuel trims are reporters, if LTFT says -10, it is telling PCM it is too rich by 10%, thus PCM attempts to correct so it reduces injector pulse width to try and get back to a zero report from LTFT, thus it goes +10.
If we have rich trim during PT, the LTFT values are negative and the PCM is removing fuel. I am ok with that. I have no idea what you are saying here:
>>PE only adds a scaled multipler
>>value to that so if trim is -10,
>>PCM is going +10, so PE is biased
>>lean and only uses the value for
>>the RPM and engine time at that time
If trim is -10, PCM is going +10???? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
if you look at the PE table, the value is small and about the same across the scale thus once that PE value is used in the PCM math to the +10 lean, the end result is still too lean so
the LTFT was rich for PT but WOT ends up too lean.
Also everyone seems to look at LTFT and tunes that to about zero but never looks at STFT which handles a plus or minus 10% so LTFT can be showing zero but engine is running off of STFT and it could be -9 or +9% without you knowing it unless you are looking at it and since engine is run on 10 minute read cycles of what STFT's are it is important not to see what the value is in that register.
So some people have what they call a pig rich condition on dyno, this is because PT was too lean ( LTFT like +14 or >), PCM is now commanding injectors to go rich, you hit PE, it adds more fuel and you end up too rich at WOT.
This is why people prefer to see LTFT a bit rich rather then lean when using a MAFT but with LS1edit you can scale PE tables to have good WOT and still tune PT close to zero.
Keep in mind the dinky 16.7 Mhz cpu of PCM has to handle up to 15,000 new calibration constants that were added by OBDII and with adaptive learning of PCM, at high loads and all the nodes (modules) talking on the bus not everything gets done exactly the way it would at lower PPMs.[/b]
<small>[ August 07, 2002, 10:58 PM: Message edited by: Team ZR-1 ]</small>
at the point of going PE, PCM looks at STFT value, then freezes them, it then attempts to zero LTFT to zero.
PE table's value is then mulitplied to what the trim value was at the point of freezing.
If the LTFT cells are used when going to WOT PE, which cells are used? Don't forget that we have 0 - 22 trim cells.
Let's not confuse fuel trims with fuel cells.
I assume your using LS1esit, look at PE temp, RPM, max multipler, hot and cold sections, they dicate when PE pccurs along then with TPS.
What cells are used would depend on if the conditions of the above are met but consider cells below 6 are low MAF freq usage and when lifting g-pedal. Take MAF max freq ( 12 to 13000 Hz) and divide that by the 23 cells, now you know the freq window eash cell uses.
I consider cells at the least 15 and 22 PE and could be as low as 14, it depends on how much load ( how big a pump the engine is sucking air volume, the higher the MAF freq is and thus clearly cell 10 would be like doing 70 MPH in 6th gear but if you dropped to 5th gear, also doinjg 70 it would go to cell 11 for engine is pumping more air in since RPM is higher.
Originally posted by Team ZR-1:
and reason why you could be rich trims during PT but lean during PE because if trims are rich, PCM is going leaner and PE only adds a scaled multipler value to that so if trim is -10, PCM is going +10, so PE is biased lean and only uses the value for the RPM and engine time at that time.
Huh? I do not understand this statement at all.
fuel trims are reporters, if LTFT says -10, it is telling PCM it is too rich by 10%, thus PCM attempts to correct so it reduces injector pulse width to try and get back to a zero report from LTFT, thus it goes +10.
If we have rich trim during PT, the LTFT values are negative and the PCM is removing fuel. I am ok with that. I have no idea what you are saying here:
>>PE only adds a scaled multipler
>>value to that so if trim is -10,
>>PCM is going +10, so PE is biased
>>lean and only uses the value for
>>the RPM and engine time at that time
If trim is -10, PCM is going +10???? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
if you look at the PE table, the value is small and about the same across the scale thus once that PE value is used in the PCM math to the +10 lean, the end result is still too lean so
the LTFT was rich for PT but WOT ends up too lean.
Also everyone seems to look at LTFT and tunes that to about zero but never looks at STFT which handles a plus or minus 10% so LTFT can be showing zero but engine is running off of STFT and it could be -9 or +9% without you knowing it unless you are looking at it and since engine is run on 10 minute read cycles of what STFT's are it is important not to see what the value is in that register.
So some people have what they call a pig rich condition on dyno, this is because PT was too lean ( LTFT like +14 or >), PCM is now commanding injectors to go rich, you hit PE, it adds more fuel and you end up too rich at WOT.
This is why people prefer to see LTFT a bit rich rather then lean when using a MAFT but with LS1edit you can scale PE tables to have good WOT and still tune PT close to zero.
Keep in mind the dinky 16.7 Mhz cpu of PCM has to handle up to 15,000 new calibration constants that were added by OBDII and with adaptive learning of PCM, at high loads and all the nodes (modules) talking on the bus not everything gets done exactly the way it would at lower PPMs.[/b]
<small>[ August 07, 2002, 10:58 PM: Message edited by: Team ZR-1 ]</small>
08-08-2002, 12:51 AM
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Re: Should L-Term readings be done at idle or cruise? I never count L-trims at part throttle. I only measure L-trims at idle and WOT only. Part throttle is useless IMO. Tony (Nineball) can shed some light on this. He helped me get my MAFT adjusted properly via email.
08-08-2002, 09:32 AM
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Re: Should L-Term readings be done at idle or cruise? >>at the point of going PE, PCM
>>looks at STFT value, then
>>freezes them,
Some peole are saying that the PCM does NOT check any fuel trim values before going PE. Where are you getting this information? I am not sure who to believe.
>>it then attempts
>>to zero LTFT to zero.
What do you mean by this? Attempts to zero LTFT to zero? How does it attempt this?
>>PE table's value is then
>>mulitplied to what the trim
>>value was at the point of freezing.
How do you know this is really true?
>>Let's not confuse fuel trims
>>with fuel cells.
>>I assume your using LS1esit
I am not confusing them. Each fuel cell (0-22) holds a LTFT value. Yes I am using LS1Edit.
>>fuel trims are reporters, if
>>LTFT says -10, it is telling PCM
>>it is too rich by 10%, thus PCM
>>attempts to correct so it reduces
>>injector pulse width to try and
>>get back to a zero report
>>from LTFT,
Understood and agreed
>>so it reduces
>>injector pulse width to try and
>>get back to a zero report
>>from LTFT,thus it goes +10.
This is where you lose me. What goes +10?
>>if you look at the PE table, the value is small
>>and about the same across the scale
I have looked at the PE vs RPM table.
I understand and agree.
>>thus once that PE value is used in
>>the PCM math to the +10 lean,
>>the end result is still too lean so
>>the LTFT was rich for PT
>>but WOT ends up too lean.
Please slow down a bit, you just lost me here. You said, “once that PE value is used in the PCM math to the +10 lean”. What are you referring to here? Do you mean that LTFT is +10 (means mixture is lean and PCM is adding fuel)? What do you mean by the “+10 lean”?
I consider myself to be quite technical, but this just makes no sense to me. You said +10 lean, and then you said the LTFT was rich for PT. That sounds like a contradiction. What is the +10 lean, is that a LTFT or a STFT?
>>Also everyone seems to look at LTFT and
>>tunes that to about zero but never looks
>>at STFT which handles a plus or minus 10%
>>so LTFT can be showing zero but engine is
>>running off of STFT and it could be -9 or +9%
>>without you knowing it unless you are looking
>>at it and since engine is run on 10 minute read
>>cycles of what STFT's are it is important not to
>>see what the value is in that register.
This made sense, until you said “engine is run on 10 minute read cycles of what STFT's are it is important not to see what the value is in that register.”
Why is it important “NOT” to see what the value is in that register? Furthermore, what do you mean by 10 minute read cycles?
>> So some people have what they call a pig
>>rich condition on dyno, this is because PT
>>was too lean ( LTFT like +14 or >), PCM
>>is now commanding injectors to go rich,
>>you hit PE, it adds more fuel and you
>>end up too rich at WOT.
This comes back to the original question. How do you REALLY know that the PCM is using a trim value (LTFT or STFT) as a variable when going PE? This just an opinion of what is going on?
Sorry if I am asking a lot of questions, I feel this information would be helpful for the entire group.
>>looks at STFT value, then
>>freezes them,
Some peole are saying that the PCM does NOT check any fuel trim values before going PE. Where are you getting this information? I am not sure who to believe.
>>it then attempts
>>to zero LTFT to zero.
What do you mean by this? Attempts to zero LTFT to zero? How does it attempt this?
>>PE table's value is then
>>mulitplied to what the trim
>>value was at the point of freezing.
How do you know this is really true?
>>Let's not confuse fuel trims
>>with fuel cells.
>>I assume your using LS1esit
I am not confusing them. Each fuel cell (0-22) holds a LTFT value. Yes I am using LS1Edit.
>>fuel trims are reporters, if
>>LTFT says -10, it is telling PCM
>>it is too rich by 10%, thus PCM
>>attempts to correct so it reduces
>>injector pulse width to try and
>>get back to a zero report
>>from LTFT,
Understood and agreed
>>so it reduces
>>injector pulse width to try and
>>get back to a zero report
>>from LTFT,thus it goes +10.
This is where you lose me. What goes +10?
>>if you look at the PE table, the value is small
>>and about the same across the scale
I have looked at the PE vs RPM table.
I understand and agree.
>>thus once that PE value is used in
>>the PCM math to the +10 lean,
>>the end result is still too lean so
>>the LTFT was rich for PT
>>but WOT ends up too lean.
Please slow down a bit, you just lost me here. You said, “once that PE value is used in the PCM math to the +10 lean”. What are you referring to here? Do you mean that LTFT is +10 (means mixture is lean and PCM is adding fuel)? What do you mean by the “+10 lean”?
I consider myself to be quite technical, but this just makes no sense to me. You said +10 lean, and then you said the LTFT was rich for PT. That sounds like a contradiction. What is the +10 lean, is that a LTFT or a STFT?
>>Also everyone seems to look at LTFT and
>>tunes that to about zero but never looks
>>at STFT which handles a plus or minus 10%
>>so LTFT can be showing zero but engine is
>>running off of STFT and it could be -9 or +9%
>>without you knowing it unless you are looking
>>at it and since engine is run on 10 minute read
>>cycles of what STFT's are it is important not to
>>see what the value is in that register.
This made sense, until you said “engine is run on 10 minute read cycles of what STFT's are it is important not to see what the value is in that register.”
Why is it important “NOT” to see what the value is in that register? Furthermore, what do you mean by 10 minute read cycles?
>> So some people have what they call a pig
>>rich condition on dyno, this is because PT
>>was too lean ( LTFT like +14 or >), PCM
>>is now commanding injectors to go rich,
>>you hit PE, it adds more fuel and you
>>end up too rich at WOT.
This comes back to the original question. How do you REALLY know that the PCM is using a trim value (LTFT or STFT) as a variable when going PE? This just an opinion of what is going on?
Sorry if I am asking a lot of questions, I feel this information would be helpful for the entire group.
08-12-2002, 11:38 PM
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Re: Should L-Term readings be done at idle or cruise? Some good, yet confusing <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> , info here <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Please, keep it coming <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Please, keep it coming <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
