interesting thing regarding FTC tables

[TT_Vert]

I logged a 100% part throttle run and i noticed a few cells that occured a very few times (1 to 4 rows in 4350)

These FTCs were as follows (the odd thing is these are the only positive FTCs I have)

FTC 8 (4 rows\Value: 8.6/7.6)
FTC 12 (1 row\Value: 7.8/7)
FTC 13 (4 cells\Value: 5.5/4.7)

I also got some FTC 15s (WOT) and I wasnt WOT at all this run)

Im assuming I shouldnt worry about the above cells as they equate to maybe a second of total engine operation but if you guys could put my mind at ease and possibly offer me an explanation what the above cells actually are and why i see a few WOT FTC 15s in there?
Thank you
Dave

[wait4me]

hi dave, what are the specs on your motor set up....
cell 15 is just very high load no pe enrichment, most people dont see this cell because normally by the time they should hit that table they go to cell 22 which is actually cell 15 but with added fuel by a percentage put in via the pe vs rpm table .. if you arent seeing all the normal cells when driving, normally that means that you have your ve table all messed up.. or your fueling situation is not good.. or if you are forced induction you have to make some changes to enable stuff differently because of how fast your motor can change vacuum now with boost..

[FLORIT]

Would you share with a novice what the "normal cells" are? And which table these FTC cells are being pulled from? In other words, when you say "Cell 15"... cell 15 of what table?

This may seem elementary, but I'm in kindergarten.

[wait4me]

ok, a perfect ve table should represent a 14.7 air fuel ratio in all points of the grid.. in every rpm and load...
"or 14.6 on some" so many things run off of this table, and that is why it is so important.. You can see that by what you have to do with it to get a cam to idle better..

Cells, are actually just predetermind blocks of the ve, and ltfts, and stfts, are the percentage of fuel the computer is having to add or take away to hit 14.7 off of the ve table at that specific "block"

If you get your ve table perfect, then tuning and drivability is easy and has very good results, not including more responsive.

like i was saying with the ve table, on ls1edit, if you have your ve table tuned correctly, then the pe vs rpm numbers work very well and are very accurate...
that number you have in the table for the given rpm, say it is 1.2306 ok so that number is the amount of fuel it is going to add to that spot on your ve.. so if it is set to 14.7 like it should, and you divide that number 14.7 by 1.2306, 14.7/1.2306 = 11.9 af ratio...
or if you put in 1.1306 the af is, 13.0

but this only works if the ve is correct....
that is what the computer is trying to correct with ltrms, and strims.... so all the other values will work correctly,
the only reason why people set the numbers of ltrims to negitive numbers is because it tricks the computer into not ever adding the fuel to correct the ve, so they can enter more or less fuel in the pe vs rpm table and it will always be a set value with nothing else being able to take out fuel or add it,

cells 0 thru 15 are the cells on your main ve table.
cell 22 is cell 15 plus the amount added to pe vs rpm.
then you have idle cells ect...
Cell 16 Automatic transmission in "Park" or "Neutral", hot idle, a/c on
Cell 17 Automatic transmission in "Park" or "Neutral", hot idle, a/c off
Cell 18 hot idle, a/c on (Manual or Automatic transmission in "Drive&quot
Cell 19 hot idle, a/c off (Manual or Automatic transmission in "Drive&quot
Cell 20 cold idle, a/c on or off
Cell 21 moderate/high deceleration / no load

[TT_Vert]

hi dave, what are the specs on your motor set up....
cell 15 is just very high load no pe enrichment, most people dont see this cell because normally by the time they should hit that table they go to cell 22 which is actually cell 15 but with added fuel by a percentage put in via the pe vs rpm table .. if you arent seeing all the normal cells when driving, normally that means that you have your ve table all messed up.. or your fueling situation is not good.. or if you are forced induction you have to make some changes to enable stuff differently because of how fast your motor can change vacuum now with boost..

i have a 2000 c5 w/ headers and vararam.

dave

[FLORIT]

Thanks for the info, wait4me. I actually understood that.

[jimmyblue]

In the Engine section there is a little bitty pair
of tables that are FTC boundaries. Think of them
as the 1/4, 1/2, 3/4 "cuts" in a 4x4 checkerboard.

On some of our PCMs, we have way kooky values
for the middle and upper RPM boundaries. This
makes cells 0,1,4,5,8,9,12,13 "accessible" and
2,3,6,7,10,11,14,15 never show up. Though, if
you have raised your rev limited above 6300RPM
you might get onto cell 15 which is highest MAP,
highest RPM. There may be other ways to get
onto cell 15 (the odds of landing right on the
50 RPM gap between 14 and 15 are slim).

[myblkss]

wait4me....so your basically saying you don't have to tune LTFT's you just have to get your VE table right and then tune WOT via PEvsRPM.

If the above statement is true how do you tune your VE table?

[Dirk_Diggler]

Using a WB run the car in open loop. Set the Open loop f/a table to 13.0:1 (1.13)and log as much data as you can hitting as many map and rpmm oints on the ve table. Wherever you are off + or - 13.0 you adjust the ve table accordingly.

[jimmyblue]

Cells 8, 12 are hard to hit because they are high MAP
at low RPM. With an automatic you would be down-
shifted before you spent any time there. Same for 13.
Most of my histograms are like tic-tac-toe - fill the
diagonal on acceleration, vertical to the low-MAP
line and then horizontal to idle again on decel.

The low-RPM cells (0,4,8,12) are pretty strongly VE
table driven although depending on where your
cell boundaries are, you may see some MAF contribution
as well.