Trying to fix negative LTrims, but VE table seems to have no effect
03-06-2006, 01:59 PM
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Trying to fix negative LTrims, but VE table seems to have no effect It's pretty weird. I've been getting -13 or so on high vacuum/low rpm cruise. I've been lowering the VE table in that (and surrounding area), but it seems to have no effect. Say you lower the entire VE table 10% for diagnostic purposes, how much of an effect should that have on your ltrims?
03-06-2006, 02:10 PM
#2
Are you making changes with the MAF still plugged in? Are you running in SD mode? Pre-2000 vehicles had two VE table, you need to modify both tables accordingly. What vehicle is this you are trying to tune? 
03-06-2006, 02:14 PM
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It's a 2000 Corvette. I'm just adjusting the primary VE table (the car uses a MAF). I figured the secondary VE table was just a backup for when the MAF fails?
03-06-2006, 02:26 PM
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Car runs on the MAF most of the time. You have to unplug it to adjust VE. Then you have to adust secondary VE to have any affect. You should upgrade to a 2001 or 2002 computer software.
03-06-2006, 03:14 PM
#6
Terry, your MAF is going to skew you attempts at trying to zero out your fuel trims. You need to disable it and adjust your secondary VE, while correlating the primary VE. This is why most people upgrade to a 2001+ bin file, it is easier to tune an SD tune. Let me know if you need more help, as I would be willing to help ... plus I have a wideband to use for more precise tuning.
03-06-2006, 04:00 PM
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Ah, I'm trying to keep a normal MAF tune, I just want it closer. In Corvettes if you go -13+ ltrims for long enough it throws a code. How does that wide band connect? I'd love to take you up on it! Know any good cheap dyno places around? That might just be easier for me.
The engine is a 383 with AFR heads, and an old MMS 229 cam.
So with a traditonal MAF tune, is the VE table not used?? I've always adjusted the MAF table for the maf I run, set the VE table to get the ltrims close to -3, and then used the PE table to add WOT fuel as needed. It's been awhile though!
The engine is a 383 with AFR heads, and an old MMS 229 cam.
So with a traditonal MAF tune, is the VE table not used?? I've always adjusted the MAF table for the maf I run, set the VE table to get the ltrims close to -3, and then used the PE table to add WOT fuel as needed. It's been awhile though!
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03-06-2006, 06:38 PM
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I've noticed this too - lowering the VE in a given cell without the MAF disabled doesn't so much change the fuel trimming as make the car 'sputter' more.
From my observations I think the MAF is doing some correction since airflow calcs are mostly MAF based (from what I've read) as long as the MAF is enabled - really the only time VE is a major factor in calculation is when in SD mode/MAF failed/off. It is referenced in the 'sanity check' against the MAF to ensure the MAF hasn't gone nuts, but you really need to be in SD mode to twiddle the pri/sec VE.
Rob (Bad30th)
From my observations I think the MAF is doing some correction since airflow calcs are mostly MAF based (from what I've read) as long as the MAF is enabled - really the only time VE is a major factor in calculation is when in SD mode/MAF failed/off. It is referenced in the 'sanity check' against the MAF to ensure the MAF hasn't gone nuts, but you really need to be in SD mode to twiddle the pri/sec VE.
Rob (Bad30th)
03-06-2006, 07:55 PM
#10
in normal operation it's a mix of maf/ve until 4000rpm, then it's all maf. either way, changing VE with MAF on won't do much for you.
the whole idea of VE tuning is to make changes without MAF, so you know exactly what effect which change in VE had. once that's done, you tune your MAF and everything is back to normal (or better normal as now you're actually properly accounting for the extra airflow)
the whole idea of VE tuning is to make changes without MAF, so you know exactly what effect which change in VE had. once that's done, you tune your MAF and everything is back to normal (or better normal as now you're actually properly accounting for the extra airflow)
03-07-2006, 08:46 AM
#11
As Marcin (RedHardSupra) said, the ECM uses both the VE and MAF for all fuelling calculations, except on steady state cruising (MAF only). You need to disable the MAF first before you start adjusting the VE table. With my wideband and HPTuners EIO you can track the deviations the VE table has from the commanded AFR and zero in the VE tables using the WB O2 error %. It is much easier and faster to dail in your VE tune using this setup. This can also be used to fine tune your MAF table. It is not a good idea to blindly scale up or down the MAF table.
Terry, I do know of a dyno place ... hit me up and we can work together on your car.
Terry, I do know of a dyno place ... hit me up and we can work together on your car.
03-07-2006, 09:07 AM
#12
Originally Posted by YellowToy/A
Car runs on the MAF most of the time. You have to unplug it to adjust VE. Then you have to adust secondary VE to have any affect. You should upgrade to a 2001 or 2002 computer software.
03-07-2006, 09:42 AM
#13
Originally Posted by Z'mnypit
Not to highjack your thread or anything but I was just curious as to what would happen it you copy & pasted the primary VE to the secondary VE table. Then when dialing in the VE you made the same changes to both tables since the numbers are the same. Would this work? Or would it be pointless. BTW this was for the pre 2001 models.
03-07-2006, 09:47 AM
#15
Originally Posted by Flame Throwing SS
Correct! You would have to make changes to the primary to keep the (when MAF enabled) higher resolution. Smooth the primary VE Table and then copy the corresponding rows from the primary onto the secondary. The secondary VE has half the resolution of the primary VE.
03-07-2006, 11:19 AM
#17
Originally Posted by Z'mnypit
So it would be better to paste after you had the primary squared away? not before?
Originally Posted by D_Run
Is that possible?