Is VE or MAF primary management?
09-02-2003, 08:36 PM
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Re: Is VE or MAF primary management? Most people I have seen recommend scaling the MAF table. I want to know why also because if the MAF is stock it shouldnt need calibration so why would that be the first step to tunning for LTFT's
09-02-2003, 10:30 PM
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Re: Is VE or MAF primary management? I would still consider the MAF the "primary" management - but since both can effect fueling to a certain point it's a matter of semantics - if the practical effects are the same. Without seeing the actual algorithm's GM uses one can only surmise, but i would expect the maf to be used to calculate the theoretical fuel requirements and then the ve is applied later on as a scalar to that value.
Don't forget to include the IFR table in the with respect to fueling changes, and also realize that, when in closed loop, non PE fueling changes actually just changes the l-trim values - your static fuel delivery is going to be the same - though your transient fueling may be slightly different.
I normally scale the MAF table by 104% starting out, and this seems to work well. I understand the arguments for not altering it, but also realize that if you have descreened your maf you are now under-reporting the flow, even changing the induction can effect how the maf meters, since it is sensitive to the flow path for about 10 inches before and after itself. A new lid alone, even with a screened maf, will make a few percentage points difference in l-trims.
Without a flow bench and a means of bolting up your entire intake path then the calibration becomes inaccurate, though precision is still maintained. 104% Seems to be a good compromise in my experience, though again, every car is different. After that I would tune with the IFR to get your l-trims in line, having first set it to the theoretical value.
The actual effect of the VE on fueling is still undefined afaik, though it definitely does have an effect. i would hold off on that initially and try and get a good baseline using the methods above. You can then experiment with the VE to see if you can address issues with outlying FTC's, and possible transient fueling issues.
Don't forget to include the IFR table in the with respect to fueling changes, and also realize that, when in closed loop, non PE fueling changes actually just changes the l-trim values - your static fuel delivery is going to be the same - though your transient fueling may be slightly different.
I normally scale the MAF table by 104% starting out, and this seems to work well. I understand the arguments for not altering it, but also realize that if you have descreened your maf you are now under-reporting the flow, even changing the induction can effect how the maf meters, since it is sensitive to the flow path for about 10 inches before and after itself. A new lid alone, even with a screened maf, will make a few percentage points difference in l-trims.
Without a flow bench and a means of bolting up your entire intake path then the calibration becomes inaccurate, though precision is still maintained. 104% Seems to be a good compromise in my experience, though again, every car is different. After that I would tune with the IFR to get your l-trims in line, having first set it to the theoretical value.
The actual effect of the VE on fueling is still undefined afaik, though it definitely does have an effect. i would hold off on that initially and try and get a good baseline using the methods above. You can then experiment with the VE to see if you can address issues with outlying FTC's, and possible transient fueling issues.
09-03-2003, 01:00 PM
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Re: Is VE or MAF primary management? Thanks for reply, Actually I don't even have LS1 edit but am trying to help some friends with. I have a 3rd gen and do my own proms.
So I guess IFR'S would be like your inj. constant setting? And if thats the case than you are making a global change through entire RPM range.
I guess I will help them scale the MAF table,especially since they have removed screens..
So I guess IFR'S would be like your inj. constant setting? And if thats the case than you are making a global change through entire RPM range.
I guess I will help them scale the MAF table,especially since they have removed screens..