Ditch Digger

I just received LS1-Edit a couple of weeks ago and have begun the tuning process. I initially adjusted my idle and drilled out my TB hole a small amount to get my IAC down. This was straightford after reading the FAQ at the top of the page. I am now adjusting my LTERM's which had been averaging +11. I have initially multiplied my MAF table by 115% in an attemp to get the average down to -4. After doing this I re-AutoTapped my car and found my values now are between -5 an +9 depending on engine load, rpm, and intake temp. It is my understanding that the only LTerm values that really matter are the ones that occur right before the engine reaches WOT. After analyzing my Auto-Tap info (from a 30min car ride)I have noticed that at anything over 30% throttle The LTerm's are between +0.8 and -4.7. My question is should I be concerned about the high LTERM's that occur at throttle percentages below 20%? By the way the car is a 98 Z28 with TTS LT's, LS6 intake, and B1 cam.

Thanks,
Darren

J&JsTA

Because your LTFTs are ranging from -'s to +'s you may need to adjust only the maf freqeuncies that match the fuel cells that are running in the +'s. Do a search on LTFTs in this forum as there are lots of threads discussing this process as well as on here http://ls1edit.slowcar.net/tuning.html ... just don't forget to check the fuel curve in the graph view in edit to ensure you still have that lovely sweeping smooth arc <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

<small>[ March 23, 2003, 06:38 PM: Message edited by: J&JsTA ]</small>

Doc99SShome

You need to realize that you have many LTFT values, and as you said, the most important one is the one taken over from part throotle into WOT. If the WOT LTFT value is 0% or slightly negative, you are fine.

If you want to reduce some of the positive ones, then you need to determine where the positive LTFT values fit into the MAF frequency table,, and only change that portion of the MAF table. In the end, it is very very important to maintain a smooth curve for your MAF table. Check your work with the graphics mode in LS1Edit, and compare the stock table to your latest MAF table.


BTW: I would never recommend to make a one time same multiplication across every cell in the MAF table. That is not the way to re-calibrate a MAF table because different portions of the table require larger or smaller modifications. This is due to the fact that the LTFT values are not all the same value.

Black LS1 T/A

My2Cents:

Injector Flow Rate Table

Normally, use your Injector Flow Rate (IFR) Table to adjust LTFT's.
Adjust IFR's downward to decrease LTFT (tells the computer the injector is smaller than what it now believes it is, so more fuel is added, which compensates for what the computer believes is a lean condition based on O2 Sensor readings, and brings the LTFT adjustment more negative).
Adjust IFR's upward to increase LTFT (opposite of what I said for adjusting downward).
The intent of the table is to introduce a constant that coincides with the injector size and the Fuel Pressure.

Theoretically, if you haven't changed the injector or changed your Fuel Pressure, you should not modify this table. If your LTFT's are out of whack, you should first look for vacuum leaks and other abnormal situations. However, modding the car can alter the LTFT's, so you may be justified in changing them if there are no problems that would induce a shift.

The logic behind zeroing or negating LTFT's is that when you go WOT, LTFT's will be zeroed, meaning no additional fuel is being dumped into the engine at WOT and tuning will be easier. It has been argued that if you can obtain positive LTFT's of a consistent value, this is just as good, as the value is predictable, and thus tunable. That argument seems to have merit to me. But, it has been my experience that when I make LTFT's zero or slightly negative, my car REALLY wakes up at WOT. It even seems more responsive at part throttle. But that is my experience.

MAF Table

This table calibrates the MAF Sensor and should be left stock if your MAF is stock. Period.
If you get an after-market MAF, in my opinion, they should supply you with or point you to a means of calibrating for it.
LS1-Edit or a MAFT or whatever could do this.

If you port or remove the screen of your MAF sensor, you have changed it (and will likely be running lean as a result of the increased airflow).
Assuming one could port the MAF at home in a consistent way, if LTFT's are positive and MAF related:
Adjust MAF values upward 1% to decrease LTFT's by 1%.
Adjust MAF values downward 1% to increase LTFT's by 1%.

So, if you are +10 on your LTFT's, scale the MAF table by a value of 105 (increases the table values by 10%), which will decrease LTFT's approximately -10. It may take a couple tries.
95 (95% multiplier decreases table values by 5%), which would raise LTFT's +5.

PE/RPM Table

Increasing the Multiplier (the value in each table entry) adds fuel at WOT.
Decreasing the Multiplier subtracts fuel from what the previous value supplied.

This is the table to use to tune your A/F ratio on the dyno (which should decrease or increase O2 Banks 1 and 2 depending on whether you have leaned or richened the mixture, respectively). O2 Bank readings are one of the tools you would use to determine if you are running rich or lean at WOT, relatively speaking, when you are on the track or the street. I've heard that values of 870 to 930 milliVolts (.870 or .930 volts) are a reasonable range for NA cars. For Forced induction, I try for no less than 920 mV; 930 mV is safer, still. There are arguments as to why you CAN'T use the O2 sensors to tune. But, everyone does, if they are not on a dyno... they ARE useful even if they are not terribly accurate from an ABSOLUTE perspective.
The keyword here is RELATIVE. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

That's my understanding of basic tuning the A/F Ratio for optimal performance.
The experts can chime in here to correct any misperceptions I may have.

Good luck!

<small>[ March 24, 2003, 10:01 AM: Message edited by: Black LS1 T/A ]</small>

Ditch Digger

Thanks alot everyone. You have given me alot to think about. I will probably log my car one more time and go from their. I did remove my MAF screen a couple of years ago so I do think that the MAF needs calibration. I will try to look at the MAF table at different points and maybe make a few more minor adjustments.

Thanks,
Darren