confused commanding 11.7 getting like 14.1
07-02-2013, 03:59 PM
#1
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confused commanding 11.7 getting like 14.1 new to tuning with hp tuners stock program pe is 1.250 which is 11.7 but going down the track Im getting like 14.1 any suggestions what this could be
07-02-2013, 05:04 PM
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Look at the AFR as RPM changes. Rising AFR could
indicate a fuel fade problem. A consistently jacked
AFR may mean a scaling error in some sensor like
the MAF, or consistently low fuel pressure.
But there is also the question of where you get
the 14.1 AFR reading, and whether the source is to
be trusted. You could have some deal like one silted
injector, misfiring all the way down track from lean
delivery and all that unused air whacks the reading
(average of the 4 per bank, or all 8 in the I-pipe).
How you know whether to trust your instrument, or
when not to, is a big deal. If you believe in garbage
then in the next step you shovel garbage into your
tune. That just gets better and better.
indicate a fuel fade problem. A consistently jacked
AFR may mean a scaling error in some sensor like
the MAF, or consistently low fuel pressure.
But there is also the question of where you get
the 14.1 AFR reading, and whether the source is to
be trusted. You could have some deal like one silted
injector, misfiring all the way down track from lean
delivery and all that unused air whacks the reading
(average of the 4 per bank, or all 8 in the I-pipe).
How you know whether to trust your instrument, or
when not to, is a big deal. If you believe in garbage
then in the next step you shovel garbage into your
tune. That just gets better and better.
07-02-2013, 05:48 PM
#6
One thing Jimmy mentioned, at least half the wide bands guys had mounted in their cars, that came across my dyno, were way off. Most read leaner than actual, but I have seen some rich as well. So many guys here go for the cheapest, instead of the best, and that too often is what you end up with.
07-02-2013, 06:03 PM
#7
One thing Jimmy mentioned, at least half the wide bands guys had mounted in their cars, that came across my dyno, were way off. Most read leaner than actual, but I have seen some rich as well. So many guys here go for the cheapest, instead of the best, and that too often is what you end up with.
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07-03-2013, 12:04 PM
#9
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My point was more that all oxygen sensor based
wideband meters are subject to exhaust oxygen
spoofing - misfires will do this, leaks will do this.
A lean cylinder or even just too wide a plug gap
to fire reliably at max cylinder pressure can push
way more unconsumed oxygen into the pipe than
is normal, whacking the reading.
Then there is the question of calibration drift,
some rigs try to provide free-air cal routines but
some, you're stuck believing that an aging sensor
stays right. Which sooner or later will be false -
sooner, if you leave it in the pipe and fail to get
it hot before firing up very, very consistently.
And the failure mode is indicating-lean, on the
core element. What the close-in electronics make
of it, varies by type - error code, or just bogus
voltage?
And do not underestimate the other electrical
externalities - ground loop errors especially, on the
single ended meter output vs your separately ground
fed PCM or scan tool auxiliary inputs. Ground offset
-will- affect your voltage reading and its displayed
AFR result, the question is how much or how little,
and what you are going to do about it. The methods
I see, tend to be software workarounds like adding an
offset value to a formula; but ground offset varies
with sensor heater load, chassis sheet metal ground
current load (do you like how AFR varies with A/C
blower motor speed?) and so on, so a fixed offset is
just bullshit that somebody likes the taste of. The
right answer is cobbling custom electronics to take
out the offset at the source. That works, but it's not
everybody's favorite hobby.
This last, can be checked with a DMM - meter output
by itself had best match logged voltage when connected,
given a consistent exhaust gas input.
wideband meters are subject to exhaust oxygen
spoofing - misfires will do this, leaks will do this.
A lean cylinder or even just too wide a plug gap
to fire reliably at max cylinder pressure can push
way more unconsumed oxygen into the pipe than
is normal, whacking the reading.
Then there is the question of calibration drift,
some rigs try to provide free-air cal routines but
some, you're stuck believing that an aging sensor
stays right. Which sooner or later will be false -
sooner, if you leave it in the pipe and fail to get
it hot before firing up very, very consistently.
And the failure mode is indicating-lean, on the
core element. What the close-in electronics make
of it, varies by type - error code, or just bogus
voltage?
And do not underestimate the other electrical
externalities - ground loop errors especially, on the
single ended meter output vs your separately ground
fed PCM or scan tool auxiliary inputs. Ground offset
-will- affect your voltage reading and its displayed
AFR result, the question is how much or how little,
and what you are going to do about it. The methods
I see, tend to be software workarounds like adding an
offset value to a formula; but ground offset varies
with sensor heater load, chassis sheet metal ground
current load (do you like how AFR varies with A/C
blower motor speed?) and so on, so a fixed offset is
just bullshit that somebody likes the taste of. The
right answer is cobbling custom electronics to take
out the offset at the source. That works, but it's not
everybody's favorite hobby.
This last, can be checked with a DMM - meter output
by itself had best match logged voltage when connected,
given a consistent exhaust gas input.
