histogram reading? need some help here.
08-23-2005, 09:39 PM
#1
histogram reading? need some help here. I have 2 cars. an A4 and an M6, cam, heads, headers, converter. HP tuner...
anyways both are not tuned right and are slow. I finally figured out how to log (you need stuff in the table) and have a few logs now. All the numbers in the histograms on the top and the side... why is there nothing to tell me what this is? All i figured out so far is the LTFT are supposed to be 0-4 +- right? Im getting numbers from 11-25. but i dont know what they represent because they are in random spots in an unlabled chart. do i have to go find the decoder ring?
Is there a class one could take? Im getting sick of the guess and check method.
The M6 car is showing retard of 4 but on the graph its at .52 - 2.8 ?? and so on. what does that mean? is this some secret code again?
I know theres posts on here answering my questions, but i would have to read 1000 posts to answer them all. A video/DVD or manual would be nice.
anyways both are not tuned right and are slow. I finally figured out how to log (you need stuff in the table) and have a few logs now. All the numbers in the histograms on the top and the side... why is there nothing to tell me what this is? All i figured out so far is the LTFT are supposed to be 0-4 +- right? Im getting numbers from 11-25. but i dont know what they represent because they are in random spots in an unlabled chart. do i have to go find the decoder ring?
Is there a class one could take? Im getting sick of the guess and check method.
The M6 car is showing retard of 4 but on the graph its at .52 - 2.8 ?? and so on. what does that mean? is this some secret code again?
I know theres posts on here answering my questions, but i would have to read 1000 posts to answer them all. A video/DVD or manual would be nice.
08-23-2005, 09:52 PM
#2
watching my O2s on the chart they both go up as the rpms go up evenly but then at around 4300 rpms B1 starts to drop masively while B2 is at 918 B1 is at 660 by 5000 rpms its at 100 where it finally drops to zero at 6000 rpms. and B2 is at 916
Bad O2 sensor?
Bad O2 sensor?
08-23-2005, 09:53 PM
#3
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up and down is MAP and across the top is RPM
there is a class you can take.... www.efi101.com They offer them at shops all around the country so just watch the schedule and wait for one in your area.
if you don't have a wideband I highly recommend you get one. I tried to tune my car with the LTFT STFT method and wanted to pull my hair out. Not to mention the stupid amounts of money wasted on gas because this method involves a LOT of driving time. Everytime you make a change you have to reset the LTRIMS and then wait for them to be learned again which takes like an hour of driving.
As far as learning...just spend a lot of time reading this forum. there are some very intelligent people on here
there is a class you can take.... www.efi101.com They offer them at shops all around the country so just watch the schedule and wait for one in your area.
if you don't have a wideband I highly recommend you get one. I tried to tune my car with the LTFT STFT method and wanted to pull my hair out. Not to mention the stupid amounts of money wasted on gas because this method involves a LOT of driving time. Everytime you make a change you have to reset the LTRIMS and then wait for them to be learned again which takes like an hour of driving.
As far as learning...just spend a lot of time reading this forum. there are some very intelligent people on here
08-23-2005, 09:59 PM
#4
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You need to select which histogram view you look
at, by what you're trying to figure out. There are
min, max, avg, last (maybe more by now).
For example if you are chasing knock retard you want
to know the maximum seen in the run, and where.
The axes for spark advance and retard are the RPM,
and the Dynamic Cylinder Air - same as in the main
spark tables, on purpose.
You want your fuel trims to be small, and any error
should be on the negative side. This means a little
rich bias that is being taken out by trimming, safer
and better than lean error. Several things to be
seen from the LTFT histogram. One, flip between
the min and max views. If you see a significant
difference, then the car is drifting while you drive
it. This is not good, it means the trimming is not
stable and therefore suspect. Possible causes are
poor O2 sensor operation (headers, age), wide
temperature swings, etc or the simple fact that
GM decided to use only half of the available cells
on some models, leaving the rest with too much
ground to cover.
Look at the max, see what your big positive values
are and where. Axes are RPM and MAP, the speed
density airflow main components. RPM and MAP can
be translated to the fuel trim cell by looking at the
boundary values tables. Draw these out and see how
the fueling trims are binned. You may want to change
the boundaries to put more resolution in play, or not.
Look at the LTFTs in terms of RPM (indicates whether
it's MAF or SD or a combination), and MAP*RPM (is the
problem better or worse at big airflows). Look at the
min view as well to see the worst of any negatives.
But in general people seem to see more positive trims.
This is either short air reading or short fuel delivery.
If you have a clean fuel filter and haven't messed with
the fuel system and the errors are bigger at low air
(hence low fuel) flows that is a pretty certain pointer
to air metering. MAF table if you buggered the MAF
or make it breathe oily air. VE table if you've been
adding back-end airflow mods and never updated it.
at, by what you're trying to figure out. There are
min, max, avg, last (maybe more by now).
For example if you are chasing knock retard you want
to know the maximum seen in the run, and where.
The axes for spark advance and retard are the RPM,
and the Dynamic Cylinder Air - same as in the main
spark tables, on purpose.
You want your fuel trims to be small, and any error
should be on the negative side. This means a little
rich bias that is being taken out by trimming, safer
and better than lean error. Several things to be
seen from the LTFT histogram. One, flip between
the min and max views. If you see a significant
difference, then the car is drifting while you drive
it. This is not good, it means the trimming is not
stable and therefore suspect. Possible causes are
poor O2 sensor operation (headers, age), wide
temperature swings, etc or the simple fact that
GM decided to use only half of the available cells
on some models, leaving the rest with too much
ground to cover.
Look at the max, see what your big positive values
are and where. Axes are RPM and MAP, the speed
density airflow main components. RPM and MAP can
be translated to the fuel trim cell by looking at the
boundary values tables. Draw these out and see how
the fueling trims are binned. You may want to change
the boundaries to put more resolution in play, or not.
Look at the LTFTs in terms of RPM (indicates whether
it's MAF or SD or a combination), and MAP*RPM (is the
problem better or worse at big airflows). Look at the
min view as well to see the worst of any negatives.
But in general people seem to see more positive trims.
This is either short air reading or short fuel delivery.
If you have a clean fuel filter and haven't messed with
the fuel system and the errors are bigger at low air
(hence low fuel) flows that is a pretty certain pointer
to air metering. MAF table if you buggered the MAF
or make it breathe oily air. VE table if you've been
adding back-end airflow mods and never updated it.
08-23-2005, 10:29 PM
#5
In the M6 car- LTFT are around 12-16 as the rpms go up, but in the lower rpms cruising they are around 25 no negatives anywhere. I think an O2 sensor is out. since bank one from 4300-up went back down to zero. Knowing that is the MAP and RPM makes alot more sence.
so if the LTFT numbers are negative=rich possitive=lean? is that right or am i backwards?
veiwing Min-max things stay about the same. My timing stayed at 22 up to 6k then as soon as i let off it jumped to 34. 4* of KR started right at 2200. I'll put a diff O2 in tomorrow and now i understand it somewhat i'll start over.
thanks for the info everyone.
so if the LTFT numbers are negative=rich possitive=lean? is that right or am i backwards?
veiwing Min-max things stay about the same. My timing stayed at 22 up to 6k then as soon as i let off it jumped to 34. 4* of KR started right at 2200. I'll put a diff O2 in tomorrow and now i understand it somewhat i'll start over.
thanks for the info everyone.
