1st time with wideband - AFR questions
11-02-2004, 10:39 AM
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1st time with wideband - AFR questions Well gang, I'm just about done with the PLX install in my 'vette. I've got a few questions as to what I should look for in trying to further tune the car. Mind you I'm not going to be making wide-sweeping and radical changes to the car (don't want to burn it up or anything) so I'm moreso just looking for 'boundaries' to look for to help me to know when to bump a bit richer/leaner, etc.
Here's what I do know at this point - please correct as necessary and add where I'm off base.
I guess my question is such:
Is my list above reasonable or even correct?
I do have a bit of part-throttle pinging under load in 6th gear (non-PE).
I'm thinking the VE table, as I don't have a need to modify the MAF table, and I've scaled my injector table for the SVO 30's (which I have). Most of my KR happens in non-PE, so I don't see a reason to modify the PE/RPM table for such, and the VE table seems to be the right way to go now.
I've still got the stock '99 LS1 'vette VE table loaded into the car. Should I switch it to something that might closer mimic my engine w/ the mods I have (like an '03 Z06 VE table or something) that was created for an engine with more efficiency (closer to my cam profile, etc.)?
My major mods are listed in my sig, but also include FLP headers w/ straight pipes, underdrive pulley, LS6 intake manifold, LS6 MAF (with the Z06 MAF table), Vararam intake system, etc.
I've heard the truck MAF table is better to use than the Z06 MAF table, and have thought about switching to this. Any comments on that?
Sorry for so many questions. Thanks for any help on this!!
Here's what I do know at this point - please correct as necessary and add where I'm off base.
I guess my question is such:
Is my list above reasonable or even correct?
I do have a bit of part-throttle pinging under load in 6th gear (non-PE).
I'm thinking the VE table, as I don't have a need to modify the MAF table, and I've scaled my injector table for the SVO 30's (which I have). Most of my KR happens in non-PE, so I don't see a reason to modify the PE/RPM table for such, and the VE table seems to be the right way to go now.
I've still got the stock '99 LS1 'vette VE table loaded into the car. Should I switch it to something that might closer mimic my engine w/ the mods I have (like an '03 Z06 VE table or something) that was created for an engine with more efficiency (closer to my cam profile, etc.)?
My major mods are listed in my sig, but also include FLP headers w/ straight pipes, underdrive pulley, LS6 intake manifold, LS6 MAF (with the Z06 MAF table), Vararam intake system, etc.
I've heard the truck MAF table is better to use than the Z06 MAF table, and have thought about switching to this. Any comments on that?
Sorry for so many questions. Thanks for any help on this!!
Last edited by AllCammedUp; 11-02-2004 at 10:55 AM.
11-02-2004, 10:54 AM
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The general part of this looks right.
I would suspect the 5.3 heads are higher than stock CR so
to suppress pinging you might either have to pull timing out
or push PE to come in a bit lower (just before current ping
begins) if this is a steady ping. If it's transient ping then
increasing VE table at mid-high RPM may be the better way
to squash it. In general cams want you to "tilt" the VE
"surface" - lower at low RPM and higher at high RPM as this
is what the cams do for airflow. More than just the "reduce
VE at idle, 400/800/1200 columns; that's only a start and
the more extreme the cam the further up from the bottom
the need to reduce VE and the more you need to beef up
the big end.
Your idle mixture may be pushed by header O2 effects, if you
see a very different trimming at Cell 0 than in midband then
this is a good possibility. Getting the car out of closed loop
(raise enable temp) and into speed density (unplug MAF)
will let you tune the low end of the table by O2 voltage with
no meddling from MAF or trimming. On your year you have to
work from the Secondary table in this "fault" mode and then
propagate the changes w/ fill-in to the Primary. If you have
idle and cruise all nice by VE tuning and then it goes flaky
when you plug in the MAF, or trims itself flaky, that just says
there's another nonideality to chase.
I would suspect the 5.3 heads are higher than stock CR so
to suppress pinging you might either have to pull timing out
or push PE to come in a bit lower (just before current ping
begins) if this is a steady ping. If it's transient ping then
increasing VE table at mid-high RPM may be the better way
to squash it. In general cams want you to "tilt" the VE
"surface" - lower at low RPM and higher at high RPM as this
is what the cams do for airflow. More than just the "reduce
VE at idle, 400/800/1200 columns; that's only a start and
the more extreme the cam the further up from the bottom
the need to reduce VE and the more you need to beef up
the big end.
Your idle mixture may be pushed by header O2 effects, if you
see a very different trimming at Cell 0 than in midband then
this is a good possibility. Getting the car out of closed loop
(raise enable temp) and into speed density (unplug MAF)
will let you tune the low end of the table by O2 voltage with
no meddling from MAF or trimming. On your year you have to
work from the Secondary table in this "fault" mode and then
propagate the changes w/ fill-in to the Primary. If you have
idle and cruise all nice by VE tuning and then it goes flaky
when you plug in the MAF, or trims itself flaky, that just says
there's another nonideality to chase.
11-02-2004, 12:42 PM
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Jimmy,
You are the man - thanks for the reply. You post a lot here, and I know a lot of people benefit from your help - it's much appreciated.
I wanted to double-check myself before doing anything, as I need to do some logging and analysis to see where I'm at, and I wanted to make sure I had a decent-enough of an idea on where I'm starting at (needed to verify I was on somewhat solid ground).
You are right - the 5.3 heads are higher CR than the 5.7 or 6.0 heads. That, coulpled w/ the TR224 cam I have are a great combo, but I need to optimize them.
Do you know of a good VE table to start with that might get me closer than the stock 99 VE table I presently use? It was built up for a much smaller cam than what I have now.
You are the man - thanks for the reply. You post a lot here, and I know a lot of people benefit from your help - it's much appreciated.
I wanted to double-check myself before doing anything, as I need to do some logging and analysis to see where I'm at, and I wanted to make sure I had a decent-enough of an idea on where I'm starting at (needed to verify I was on somewhat solid ground).
You are right - the 5.3 heads are higher CR than the 5.7 or 6.0 heads. That, coulpled w/ the TR224 cam I have are a great combo, but I need to optimize them.
Do you know of a good VE table to start with that might get me closer than the stock 99 VE table I presently use? It was built up for a much smaller cam than what I have now.
