VE changes to light throttle, higher RPM cells?
07-17-2004, 03:02 PM
#1
Moderator
Thread Starter
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
VE changes to light throttle, higher RPM cells? Chasing the MAF/VE monkey around the tree after
swapping over to a straight Delphi MAF and table.
Seems my worst positive LTFTs show at light throttle,
higher-RPM - cells 1 & 2 especially (these being at
custom boundaries, 1000-2000 and 2000-4000RPM,
<40MAP). They are low-TPS%. I am thinking the low
throttle angle is a special challenge for the VE table,
as here it is having to model the throttle blade's
choke effect with some reasonable accuracy.
Do any of our VE gurus have an idea of whether
the speed-density calc is part of the fuel shot in
this regime? With a ported, de-ridged TB I can see
where the low-TPS% character of VE would really
(potentially) be "bent" - certainly 5%, 10%-ish
airflow unshrouding is not out of line with the amount
of material I hogged back. While I'll probably dick with
it regardless, a word from the wise wouldn't go
completely ignored
on this fine Saturday
afternoon for tuning.
swapping over to a straight Delphi MAF and table.
Seems my worst positive LTFTs show at light throttle,
higher-RPM - cells 1 & 2 especially (these being at
custom boundaries, 1000-2000 and 2000-4000RPM,
<40MAP). They are low-TPS%. I am thinking the low
throttle angle is a special challenge for the VE table,
as here it is having to model the throttle blade's
choke effect with some reasonable accuracy.
Do any of our VE gurus have an idea of whether
the speed-density calc is part of the fuel shot in
this regime? With a ported, de-ridged TB I can see
where the low-TPS% character of VE would really
(potentially) be "bent" - certainly 5%, 10%-ish
airflow unshrouding is not out of line with the amount
of material I hogged back. While I'll probably dick with
it regardless, a word from the wise wouldn't go
completely ignored
on this fine Saturday afternoon for tuning.
07-17-2004, 04:59 PM
#2
TECH Addict
Join Date: Feb 2004
Posts: 2,826
Likes: 0
Received 0 Likes
on
0 Posts
The VE table is a pain in the buttox. Yes, you can use the VE table to smooth other differences in your trims within cells...At least I think that is what you asked. I am working on it myself...very time consuming without a wideband O2. (we really need a wideband group purchase) However...(!!!)...The real pain in the butt is that other fueling tables affect your trims too.
07-17-2004, 07:32 PM
#4
Originally Posted by Another_User
The VE table is a pain in the buttox. Yes, you can use the VE table to smooth other differences in your trims within cells...At least I think that is what you asked. I am working on it myself...very time consuming without a wideband O2. (we really need a wideband group purchase) However...(!!!)...The real pain in the butt is that other fueling tables affect your trims too.
I too wish it was simpler - it's not.
07-17-2004, 07:54 PM
#5
Moderator
Thread Starter
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
Well, what I did this afternoon is this:
1) I fiddled the upper-left corner of my VE table
upward by +2, everywhere to the left of where
VE "jumps up" by 5. I observed that the stock
VE table is "lumpy" (see pic) - VE goes up, down,
up, down. I hand-smoothed this (the upper part
of the pic) just because it seemed unreasonable
that VE would be that "busy".
2) I went driving & logging. Afterward I looked at the
drift of my upper-left-FTCs vs time (second pic).
They all drifted negative by a couple of points. The
shift was roughly 1:1 with the ratiometric change in
VE I made.
So it looks like, to me, the VE has a really big effect on
these lower-airflow cells (like it is almost totally in charge)
and if you target the same [RPMxMAP] box as represents
your given FTC boundary, you can mess around these
low-mass-airflow cells very directly to your liking. More
VE pushes LTFT negative.
Just because you're stabbing in the dark, doesn't mean
you can't hit what you were aiming at
1) I fiddled the upper-left corner of my VE table
upward by +2, everywhere to the left of where
VE "jumps up" by 5. I observed that the stock
VE table is "lumpy" (see pic) - VE goes up, down,
up, down. I hand-smoothed this (the upper part
of the pic) just because it seemed unreasonable
that VE would be that "busy".
2) I went driving & logging. Afterward I looked at the
drift of my upper-left-FTCs vs time (second pic).
They all drifted negative by a couple of points. The
shift was roughly 1:1 with the ratiometric change in
VE I made.
So it looks like, to me, the VE has a really big effect on
these lower-airflow cells (like it is almost totally in charge)
and if you target the same [RPMxMAP] box as represents
your given FTC boundary, you can mess around these
low-mass-airflow cells very directly to your liking. More
VE pushes LTFT negative.
Just because you're stabbing in the dark, doesn't mean
you can't hit what you were aiming at
07-17-2004, 08:10 PM
#6
TECH Addict
Join Date: Feb 2004
Posts: 2,826
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by jimmyblue
Well, what I did this afternoon is this:
1) I fiddled the upper-left corner of my VE table
upward by +2, everywhere to the left of where
VE "jumps up" by 5. I observed that the stock
VE table is "lumpy" (see pic) - VE goes up, down,
up, down. I hand-smoothed this (the upper part
of the pic) just because it seemed unreasonable
that VE would be that "busy".
2) I went driving & logging. Afterward I looked at the
drift of my upper-left-FTCs vs time (second pic).
They all drifted negative by a couple of points. The
shift was roughly 1:1 with the ratiometric change in
VE I made.
So it looks like, to me, the VE has a really big effect on
these lower-airflow cells (like it is almost totally in charge)
and if you target the same [RPMxMAP] box as represents
your given FTC boundary, you can mess around these
low-mass-airflow cells very directly to your liking. More
VE pushes LTFT negative.
Just because you're stabbing in the dark, doesn't mean
you can't hit what you were aiming at
1) I fiddled the upper-left corner of my VE table
upward by +2, everywhere to the left of where
VE "jumps up" by 5. I observed that the stock
VE table is "lumpy" (see pic) - VE goes up, down,
up, down. I hand-smoothed this (the upper part
of the pic) just because it seemed unreasonable
that VE would be that "busy".
2) I went driving & logging. Afterward I looked at the
drift of my upper-left-FTCs vs time (second pic).
They all drifted negative by a couple of points. The
shift was roughly 1:1 with the ratiometric change in
VE I made.
So it looks like, to me, the VE has a really big effect on
these lower-airflow cells (like it is almost totally in charge)
and if you target the same [RPMxMAP] box as represents
your given FTC boundary, you can mess around these
low-mass-airflow cells very directly to your liking. More
VE pushes LTFT negative.
Just because you're stabbing in the dark, doesn't mean
you can't hit what you were aiming at
1) HPtuners uses a percentage number, but the real number used on the VE table is in the 1000s and you can never match that.
2) At certain RPMs (I forgot if it was high or low...go figure) the readings from the sensors get very "flat" (low resolution), and in reality prevent the VE table from really being a smooth transition. I have been shaping my VE table for some time now, and I have noticed a "step" effect as my trims start to fall into place. There are only a few spots that aren't completely following this though, which could be because of EGR , or any number of things. I am very interested to see how my VE table looks when I am done. It may take me a while though.
I think the real key is to smooth out the lumpiness in the trims. That should result in smoother running and better transient changes. I think average trims sucks because in reality you could have half your trims positive and half of them negative...I can't imagine that makes for good drivability.
