I got my lc1 wideband all setup and running, and almost all the way down the drag strip I am @ 10 to 10.5 air/fuel. I have a 94 Z28, with mostly bolt ons and a small cam. I have tunercat to tune the car, and I have been looking around the tables some, trying to learn. I haven't really changed anything fuel or spark wise, but I need to concentrate on fuel. From searching I have learned that I rely on the maf to calculate fuel, and the VE tables are for speed density as a backup (correct me if I am wrong). With that being said, and my a/f remaining relatively stable at 10-10.5, which tables should I mess with? Should I try to change the MAF calibration tables? Will that mess up any of my part throttle driving (which still remains around 14.7 like it should). Do I add to the maf table to lean it out, or subtract from it to lean it out, and what are good increments to try so as to not go too lean? I ran a 13.1 @ 109 today consistantly, and I think I can join the 12 sec. club if I could lean it out a bit. I have read that 12.5 a/f is a good starting point for WOT as long as there is no detonation.

Sorry if these questions are answered elsewhere, but the search strings I tried didn't really turn up the explanation I am looking for on which tables to tweak. Please point me in the right direction!!! THANKS!

 

The only table you want to change for WOT fueling is %Change to fuel/air ratio vs. RPM at WOT. Lower the values in that table to lean it out. If you are too rich/lean at only certain RPMs just change those. Lower everything if it's the same everywhere. You can find the formula this table uses with a search but if I recall correctly reducing the values by 10 is roughly equivalent to 1 point on a wideband.

 

You need to use a data logging program and see what the blm are at when you hit WOT. If your having high blm's (above 128) then you need to address that first. You would have to adjust the MAF to have the normal driving blm around 128 or less. If you don't then when you hit WOT the computer adds the aditional fuel on top of what is in the %Change to fuel/air ratio vs. RPM table. That leads to erratic WOT A/F because the blm may not be the same everytime you hit WOT. You can try the WOTblmblocker program but I found it worked for 1st gear and then not after the shifts.

 

In datamaster, lterm's stay around 128 to 135, and sterms range from 112 to 138 during regular driving. Under WOT, everything pretty much locks in at 128, lt and st counts. Under WOT fuel trim cell 18 is used.

So what your saying is I need to calibrate the maf so the regular driving blm's are 128 or less. I am looking at the maf cal tables right now, they are hz vs. gm/sec. What is the general way to change this table, or are my blm's decent enough for me to not worry about this right now? Thanks for the help so far guys!

 

As long as your blm is 128 when you goto WOT then don't worry about it. You're close enough by the sounds of it.

 

I figured I would start with a small change, so I pulled 3% out of the %change to fuel/air ratio vs rpm @wot table. I didn't expect much of a change on the wideband, and I saw no change, still 10-10.3 across about 2000 rpm to 5700 rpm. I pulled about 4% more (roughly 7% total from stock) and I MIGHT have seen the a/f move to about 10.5, which is in the right direction, but any variable might have caused that. Tomorrow if I get time, I want to take out about 7% more to see what happens, but I want to make sure I don't go too far with it. Do you guys usually modify this table in larger increments? I'm trying to take small steps, as I don't want to cause any lean detonation @ wot!

 

double posted.......

 

yeah you need to take out way more than that.

On a stock tune, I take out like 50-70% in the high rpm region. (~4800-6000). At lower rpm the stock value is more reasonable, but can still be reduced slightly in some cases.