How to make sure wideband is accurate in hptuners
03-20-2015, 12:40 AM
#1
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How to make sure wideband is accurate in hptuners I hooked my wideband up today and I noticed the display would display something like 14.13 at lambda 1.0 or around it. How do I know I have the voltage offset correct in hptuners. I found a formula for my wideband I just want to make sure when hptuners says I'm at 1.0 I actually am rather than tuning in circles. The lambda/afr is never steady so how do I know?
03-20-2015, 09:54 AM
#3
Moderator
It's not always that simple Ron, the HPT formula includes a multiplier and an offset.
By comparing my AEM gauge with the HPT scanner display I noticed they agreed at AFR 14.7 (lambda 1.0) but not at e.g. 12.0 or 16.0.
While the built in multiplier for AEM was .50 with offset 10, I had to change the multiplier to .53. For my 2nd AEM wideband I needed a multiplier of .52.
By comparing my AEM gauge with the HPT scanner display I noticed they agreed at AFR 14.7 (lambda 1.0) but not at e.g. 12.0 or 16.0.
While the built in multiplier for AEM was .50 with offset 10, I had to change the multiplier to .53. For my 2nd AEM wideband I needed a multiplier of .52.
03-20-2015, 09:56 AM
#4
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>Put the car in closed loop. It will run at lambda of 1.0
Not true. You can prove this to yourself by changing
the O2 switchpoint values and see that the wideband
AFR reading moves, but closed loop remains the deal.
Like, I saw 0.500 volts putting a truck at 13.5:1 AFR
and moving it to 0.350V, like the cars use, made it
shift to 14.5-ish. There is a slope to the narrowband
volts-vs-lambda transfer function.
Now, as to trying to figure an "offset" as if it would
be any kind of consistent and repeatable - forget it.
You are trying to comp a varying chassis ground
current situation with a made up fixed number. If
you want to take out the grounding issues, you
either rewire so that wideband power ground is no
different than OBD connector ground, under all
load conditions (wideband heater power being the
main issue with units that common up the signal
and power grounds) and including all branches of
cabling. Or, you interpose an instrumentation amp
that will take you across varying ground:ground
offsets cleanly (this works on LM-1 with its 12' or
so of post-cig-lighter common ground run, which
can't help but jack the output reference away from
chassis / OBDII, which still differ from each other).
Not true. You can prove this to yourself by changing
the O2 switchpoint values and see that the wideband
AFR reading moves, but closed loop remains the deal.
Like, I saw 0.500 volts putting a truck at 13.5:1 AFR
and moving it to 0.350V, like the cars use, made it
shift to 14.5-ish. There is a slope to the narrowband
volts-vs-lambda transfer function.
Now, as to trying to figure an "offset" as if it would
be any kind of consistent and repeatable - forget it.
You are trying to comp a varying chassis ground
current situation with a made up fixed number. If
you want to take out the grounding issues, you
either rewire so that wideband power ground is no
different than OBD connector ground, under all
load conditions (wideband heater power being the
main issue with units that common up the signal
and power grounds) and including all branches of
cabling. Or, you interpose an instrumentation amp
that will take you across varying ground:ground
offsets cleanly (this works on LM-1 with its 12' or
so of post-cig-lighter common ground run, which
can't help but jack the output reference away from
chassis / OBDII, which still differ from each other).
03-20-2015, 01:09 PM
#5
Jimmyblue.
Are you saying then that the factory calibrations have the car running at something other than stoich in closed loop?
I've never changed those switch points in my tunes.
Ted
I use the AFX wideband. The display never sits still long enough to do a great comparison between it and HPT.
I agree with Jimmy about doing all you can with grounds to get that offset fixed.
Are you saying then that the factory calibrations have the car running at something other than stoich in closed loop?
I've never changed those switch points in my tunes.
Ted
I use the AFX wideband. The display never sits still long enough to do a great comparison between it and HPT.
I agree with Jimmy about doing all you can with grounds to get that offset fixed.
03-20-2015, 01:31 PM
#6
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My experience is that different platforms have some
different tune file settings and some different wideband
outcomes, stock:stock. Therefore closed loop mode in
itself, cannot guarantee true stoich "black box" style.
"Two men say they're Jesus. One of them must be wrong..."
- Dire Straits, "Industrial Disease"
I'm saying that the relation of narrowband switchpoint
to true stoich is arbitrary (tune file) and variable (exh
gas composition, shoot-through, misfires, etc.) and
that closed loop operation therefore is not necessarily
going to put you to where 14.7:1 intake mixture equals a
EQ=1.000 reading at the end of that chain. You can't
depend on normal narrowband closed loop gas as a
"reference source". It's got too much uncertainty in it.
different tune file settings and some different wideband
outcomes, stock:stock. Therefore closed loop mode in
itself, cannot guarantee true stoich "black box" style.
"Two men say they're Jesus. One of them must be wrong..."
- Dire Straits, "Industrial Disease"
I'm saying that the relation of narrowband switchpoint
to true stoich is arbitrary (tune file) and variable (exh
gas composition, shoot-through, misfires, etc.) and
that closed loop operation therefore is not necessarily
going to put you to where 14.7:1 intake mixture equals a
EQ=1.000 reading at the end of that chain. You can't
depend on normal narrowband closed loop gas as a
"reference source". It's got too much uncertainty in it.
03-20-2015, 02:22 PM
#7
Got Ya. I've noted the differing switch points in various tune files.
Sort of seems that the sad reality is that we have to "trust" that our cheap widebands read accurately because we have no good calibrated reference point. Or more correctly, points.
One of my tuner buddies bought a bottle of Test Gas to check his AFX. He says it's off by quite a bit.
With only one ref point, what do you know? Is it an offset or slope issue?
A can of worms for sure.
Good song Industrial Disease
Sort of seems that the sad reality is that we have to "trust" that our cheap widebands read accurately because we have no good calibrated reference point. Or more correctly, points.
One of my tuner buddies bought a bottle of Test Gas to check his AFX. He says it's off by quite a bit.
With only one ref point, what do you know? Is it an offset or slope issue?
A can of worms for sure.
Good song Industrial Disease
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04-20-2015, 01:25 AM
#8
I was going to post a new thread regarding ground offsets but maybe someone can help me in here since it's being discussed.
I have a Innovate W/B and I remember reading a while back about the ground offset issues with their system. I had a web page bookmarked but I lost it when the computer went **** up.
What is ground offset and how do you measure for it? I've googled the **** out of and have come up empty handed. If someone could point me in the right direction I would appreciate it.
J
I have a Innovate W/B and I remember reading a while back about the ground offset issues with their system. I had a web page bookmarked but I lost it when the computer went **** up.
What is ground offset and how do you measure for it? I've googled the **** out of and have come up empty handed. If someone could point me in the right direction I would appreciate it.
J