Dyno pulls get better, but LTFT still a problem

[03_Z06_Blue]

I got the 1.4 SW in late September and have done fine with editing to modify fan turn on, CAGS, and the rev limiter. I did the first dyno pull with my 2003 Z06 on October 16, and got a 348 RWHP baseline. Using the table on the scanner, plus the wideband input during the pull, I saw that the car was rich, so off came the filter cover to fully expose the filter (sometimes called the zip tie mod). The pull with cover removed was 12 higher, with a 360 RWHP. The scanner and dyno wideband showed the car had gotten leaner, and that is where the power came from. I have since added a Vararam air intake system, which leaned it out a bit judging by additional increase in my positive LTFT. I also jumped into the edit and adjusted PE to lean it more. Back to the dyno today showed 370 RWHP, with an AFR close to the high 12:1 ideal, but still a bit lean in spots. Anyway, this tuning really works.

On the scanner table, my longs show about 15 % positive. I have read that I should get it down to zero, but am having no success. My histogram reads the advance and knock retard sections, but no short or long trims or air fuel. I have read the 1.5 vers VE thoroughly. First of all, which PID should I be using the LTFT (SAE) or the LTFT avg. I ended up loading both short and long avg and SAE PIDs, which show on the table, but still nothing on the histogram. I have right clicked on the histogram and set avg and then last read, but still no response. I figure that once I can read the values on the histogram, I can deal with "fixing" the fuel settings to neutral. How about some hints??? I must be doing something wrong, or not doing something that is required.

[03_Z06_Blue]

Looks like some folks are reading about how I can't read the LTFT or STFT on the scanner histogram, but so far haven't been able to help me.

How about me doing this??? I can read the LTFT on the scanner table, and typically they run about +15. So, can I just go into the Primary VE table and drop the LTFT by multiplying through x 0.90 . This will drop every cell by 10% of its former value, I believe. This should at least get most of my cells closer to zero. Is this a good idea???

[cbota]

Im no expert but I believe if you increase your ve table that makes the LTFT go -, you can reduce the IFR and your LTFT will go -, or you add to your MAF and that also will lower your LTFT. Someone will correct me if this is wrong but I believe its right.

Looks like some folks are reading about how I can't read the LTFT or STFT on the scanner histogram, but so far haven't been able to help me.

How about me doing this??? I can read the LTFT on the scanner table, and typically they run about +15. So, can I just go into the Primary VE table and drop the LTFT by multiplying through x 0.90 . This will drop every cell by 10% of its former value, I believe. This should at least get most of my cells closer to zero. Is this a good idea???

[03_Z06_Blue]

Thank You, Cbota;

So I would have to increase the VE Table by multiplying through by 1.1, to lower the cell readings. As you suggested, we'll see if others agree that is the correct direction to go. I am looking to move them all since I can't read the scanner histogram, just to get them all closer.

Thank You

[blue_falcon]

If your LTFT's are positive you add to the VE if they are negative then you subtract

[03_Z06_Blue]

Thank You, Cbota and Blue Falcon;

I raised the VE table 8% and am evaluating the effect. I also figured out how to get the scanner histogram to work. I re-loaded the default PIDs and the histogram lit up.

It is starting to make sense now. I'll get each cell on the histogram just a bit negative on average LTFT; then I'll go back and adjust the PE AFR curve.

Thanks again

[03_Z06_Blue]

After I raised the VE table 8%, and verified the I could read the LTFT and STFT on the scanner histogram, I disconnected the car battery for about 24 hours (since it was raining outside). I am not sure if this wipes the trims clean and lets you start over, but I figured it was safe and would help.
I will check it out slowly for a bit. I am still not too cool on disconnecting the MAF. We'll get some experience with this firstl.

Thanks again

[corpsvette]

I'm a newbie but I am pretty sure instead of disconnecting the battery, you can go into the scanner under the Tools->VCM->Fuel&Spark and you can reset the fuel trims from there before each logging event, if I understand you right in what you are trying to do. Hope I have helped.

JIm K.

[03_Z06_Blue]

Thanks Jim;

You had a good suggestion, and it helped me. I followed your path, and confirmed it with a Forum search, and it works. I reset my fuel trims per your suggestion, and when I started the motor my LTFTs were at zero.

Friday, when the roads are dry, I'll try to fill all the cells, to see how close just bumping the entire VE table up x 1.08 made the cells. This should get me started.

Thanks for the help,
Paul