Magyver

All my logs w/MAF connected show my LT FTs to be high. I disconnect the MAF and voila 75% of the LT FTs are fixed as far as not adding fuel. The numbers . With the MAF connected I get all red cells with numbers ranging from 7 to 24. With it disconnected I get from -15 to 9. Some runs majority of the log has -4 to 9 and holding for a lot of the recorded time. My MAF

luv2spd

iTrader: (1)

Ok, the accepted method to tune these days is to do it w/ ve and maf freq instead of scaling the ifr like we used to do. Keep logging with the maf unplugged and modify the ve to get the ltfts in line. When totally done with this, plug in the maf, reset fuel trims and do more logging. Multiply your maf table by a percentage to get the trims back to where they were when the maf was unplugged. Mine used to be like yours but now they're pretty close even with the maf plugged in. Getting the ve table right should bring the ltfts closer with the maf plugged in and scaled properly. Example: you got your ltfts in line with maf unplugged via the ve table. Now, you plug maf back in and on average your ltfts are +7. Mulitply the maf table by 1.08 or 1.09 or so to get them slightly negative again.

jimmyblue

iTrader: (11)

Think about why your MAF might be so bent... contamination,
buggery or big-cam reversion problems are the most common.
All this experiment shows you is that the MAF and the SD air
measurements / calculations are in big disagreement. Expect
a large, untuned cam to be way off down low (rich) and up top
(lean) by speed-density while the MAF (unmolested) should be
accurate up top and confused (but lightly weighted in the air
calcs) down low.

I don't think you can put much trust in your trims until you
know for a fact that your O2s are working right, all the time,
with the headers. This is often not the case, LT cars see a lot of
recent-driving-history push-around. A borrowed wideband would
do you a world of good I expect.

Magyver

Wideband is needed for sure. My buddy needs to order some piece to make his setup complete. I will be using that once he orders the final piece.

Magyver

The changing part is a bit confusing. Which method should I use here?

A. In the VCM Editor>Edit>Engine Diagnostics>General>MAF Sensor Fail Frequency = 0. This will set a P0103 code and turn on the SES light. Don’t worry about the light at this time.
B. In the VCM Editor>Edit>Engine>Spark Advance>Main Spark vs. Airflow vs. RPM Open Throttle/Moving. Copy the High Octane table to the Low Octane table. The computer reverts to the low octane table when MAF is unplugged, this will assure optimal timing.
C. Start the VCM scanner>Histogram display. File>Connect then Tools>VCM Controls>Fuel & Spark>Fuel Trim Learn>Reset Fuel Trims.
D. Changes to the LTFT’s do not take effect immediately – the PCM requires at least 50 minutes or roughly 100 miles to allow for the PCM to relearn it's fuel curve. Try not to enter PE mode while driving and logging for this procedure. Stop logging and save the log. Do NOT turn off the engine until the log is saved or it will be lost. Go to VCM Scanner>Histogram display>LTFT's. Open the VCM Editor>Edit>Engine>Airflow>Main VE and select Primary VE vs. RPM vs. MAP.
E. The goal is to get ALL LTFT’s between 0 and -4. Positive LTFT's indicate fuel is being added because of a lean condition. Richen this cell by increasing the VE table value by the amount of the LTFT value. The operation is opposite for negative LTFT's.
If LTFT = (4), VE cell value is 67, result would be (67)+(4)=71 - increasing the VE, which is adding fuel. If the LTFT was (-4), the result would be (67)+(-4)=63, decreasing VE and thus reducing fuel. To decrease LTFT values, a smaller number or number closer to zero, ADD the difference between the positive LTFT value and zero to the corresponding cell in the VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs. MAP table. To increase a LTFT value, a larger number or number farther away from zero, SUBTRACT the difference between the LTFT value and zero and SUBTRACT from the corresponding cell in the VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs. MAP table. For example, In the VCM Scanner>Histogram display, the (.8, 40) cell, 800 RPM's and 40 kPa, is 4. To bring the VCM Scanner>Histogram display>LTFT cell (.8, 4.0) DOWN to 0 from 4 ADD 4 to the (.8, 4.0) cell in the VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs. MAP table. If the VCM Scanner>Histogram display>LTFT cell (2.0, 30) is -10, SUBTRACT 10 from the (2000, 30) cell in the VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs. MAP table to bring it UP to 0. This will not work out exactly but will be VERY CLOSE.
F. Repeat steps D-F until ALL values in the VCM Scanner>Histogram display>LTFT are between 0 and -4. Try to complete this on the same day for best results as LTFT values can vary +-4% per day.
G. Once all values are between 0 and -4, look at the VCM Editor>Edit>Engine>Airflow>Main VE>Primary VE vs. RPM vs. MAP>3D Surface graph. If the 3D Surface graph looks choppy, click on polynomial smoothing ONCE. This will smooth out the table values and provide a more crisp throttle response. Now rescan, and do step E.

or

1: Unplug MAF (Replace with strait bellows if you do not have intentions of ever using a MAF again ie. always speed density.)
2: Disable the SES lights for MAF codes P0101, P0102, P0103 (No check engine light.) Do not completely disable the codes or the PCM will not fall into SD mode. Only turn off the SES light, DO NOT DISABLE THE CODES THEMSELVES!
3: Start up your scanner. Start up your histogram. Now, click File then connect. Go to tools then VCM Controls. Click on Fuel & Spark. Reset Fuel Trims.
4: Drive around at a MINIMUM of 15 minutes. Try not to floor it but if you do it seems to be ok.
Stop logging, save data, do not turn off engine until you save your data or you will lose your log. Now, look at your ltft's. Open up your editor and go to Edit>Engine>Airflow and look under MAIN VE click on Primary VE vs RPM vs MAP. Click on that.
5: Let's say at .800, .28 which is equivalent to 800 RPM's you have 4 which is equal to +4. For ALL YOUR TRIMS you want between 0 and -4, so what I do is do whatever it takes to get to zero. Easy rule of thumb here if you want number smaller, add you want number bigger subtract. So, we want to bring that DOWN to 0 so ADD 4 to .800, .28. Let's say 2.0, .20 is -10, SUBTRACT 10 from 2.0, .20 to bring it UP to 0. This will not work out exactly but will get your PRETTY CLOSE. Do this for all values until everything is between 0 and -4.
6: Repeat steps 3-5 until ALL values are between 0 and -4. Try and do this all in same day for best results.
7: Once all values are between 0 and -4, look at your 3d graph. Pretty choppy huh? Click on polynomial smoothing ONE TIME. This will take a lot of choppiness out. Now rescan, and do step 5.
8: Copy High Octane table to the Low Octane Table (computer reverts to low octane table when MAF is unplugged, this assure optimal timing)

luv2spd

iTrader: (1)

I don't know what you mean by "changing part is confusing." Basically you can either enter 0 into the MAF Sensor Fail Frequency or just unplug the maf. Then copy the high octane spark table to the low octane, reset fuel trims, and log. When your done logging you can look at your ltft histogram, right click to copy. Go into your editor and right click on the main ve table and hit paste-add. This will fill in the table for you. Once you get it somewhat close with the above method, you can disable ltfts in the editor, load that tune into your car, and rescan using the stfts. They update really fast. Then you simply copy paste like you did before.

Magyver

ok...
question. after i copy the high octane spark table to the low ocatane to do i write to the VCM?

bmfcamaro

iTrader: (1)

yes you do

Magyver

You guys have been a great help.

It's all starting to click now. I just had to place what was written in the threads I've read and see what is what in the hp tuner software.

luv2spd

iTrader: (1)

No problem man!