Idle Surging and Low End VE Table Accuracy
05-12-2007, 01:00 AM
#1
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Idle Surging and Low End VE Table Accuracy Here are three pictures that show the effect of a very small
difference in a tune. One thing only was changed; the 400RPM
column of the Primary VE table was multiplied by 1.1 in the
"plus10" tune.
The first pic shows the original tune (VE table is a blind guess
but seems right at 800RPM). Small throttle blips settle clean
and RPM does not undershoot the 750RPM target by much.
Second pic shows the tune with the 400RPM column increased.
Note the full scale undershoot on MAP and how far RPM dips
(below 400RPM) before rebounding. Also see that the rich blip
on the O2s is larger and lasts longer by a good bit. The car even
stalled out on me once with this tune.
Third pic is showing an even worse surge series off the same +10%
tune. This may be throttle cracker (1MPH) joining the fun.
At any rate I found this difference interesting and if you are having
a mixture surge problem the 400RPM column (which is hard to tune
as you never go there on purpose) may want you to do some of
the same style variation and observation. Just 10% can be a
matter of life or death, as it were.
difference in a tune. One thing only was changed; the 400RPM
column of the Primary VE table was multiplied by 1.1 in the
"plus10" tune.
The first pic shows the original tune (VE table is a blind guess
but seems right at 800RPM). Small throttle blips settle clean
and RPM does not undershoot the 750RPM target by much.
Second pic shows the tune with the 400RPM column increased.
Note the full scale undershoot on MAP and how far RPM dips
(below 400RPM) before rebounding. Also see that the rich blip
on the O2s is larger and lasts longer by a good bit. The car even
stalled out on me once with this tune.
Third pic is showing an even worse surge series off the same +10%
tune. This may be throttle cracker (1MPH) joining the fun.
At any rate I found this difference interesting and if you are having
a mixture surge problem the 400RPM column (which is hard to tune
as you never go there on purpose) may want you to do some of
the same style variation and observation. Just 10% can be a
matter of life or death, as it were.
05-12-2007, 11:58 AM
#2
I might try that. I have been having some probelms with hunting with the clutch pushed in and slowing down. I put my 400 Throttle Cracker table to 0 and that seemed to clear it up. Can you post your VE table as a reference to see how much you took out. If I am reading this clearly you added fuel down in the 400 table and the car acted up?
08-15-2007, 09:19 PM
#3
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OMG! Seems to be my problem. I suspected it was something that wasn't readily apparent to a rookie like me. Time to go experiment--again. Thanks for the tip--good info.
