racecar

Looking at my scan from a road racing session, the LTFT are pretty good 4-7 at mid throttal, it's just at WOT they immediately go to 25, and the wideband is rich at 10.8. Why is the computer adding all of this fuel, and it is allready too rich?? I tried SD tuning and I give up. RedHard sent me a VE table that was a good starting point, but the more I tune, the worse it gets, and I done driving a SD tune that runs like . I am just stuck with my MAF, that's OK with me, but it appears that the LTFT are overactive. Anyone got a cure??

jimmyblue

iTrader: (11)

There is some fuel trim cell that is +25, that you entered
PE mode (open loop) from. You carry the baggage with
you if it's positive. Add FTC (Fuel Trim Cell) to the logged
params and track it down. In fact it would probably help
you to look at the HPTuners histogram for fuel trims and
compare that to the fuel trim cell map you are under,
this is found in the Open & Closed Loop fueling, FTC RPM
and FTC MAP boundaries that make a tic-tac-toe board.
Locate the operating region that has the trouble and
tweak it up (or, if it's all a mess and you're getting by
only on trimming, a wholesale retuning following one of
the method writeups).

racecar

Thanks Jimmy, I'm trying to find how to insert the fuel trim cell chart. Is it a sensor, or a PID? and what do you use for the X header and Y header?? I'm a CAD jockey, show me an Icon and I can make it work, but setting it up is a real challenge.

racecar

Got it working, looking at data now, very interesting.

racecar

OK, I see a clear pattern here. I'm at 4000rpm MAP100 fuel cell 20 and LTFT=7 part throttal, then I go to WOT and at 4400rpm MAP100 fuel cell 20 LTFT is 25. So what do I tweak here, the VE table??? Where is this fuel cell 20??

RedHardSupra

iTrader: (1)

i rarely look at fuel trim cells. just do your ve until your wb%error is ~0 everywhere

racecar

I can probably get the WB right at WOT by working with the PE and OLFA. What really puzzles me is when the LTFT jumps to +25 at WOT. If I get the VE table worked out better, will the LTFT stop jumping to 25.??

ZL1Killa

iTrader: (17)

u won't ever get 0%error but what u can also do is dial in the VE table using fuel trims by disabling the MAF but leaving CL mode on.

if you get the VE table in and MAF within so far a percentage of each other the LTFT's will go down, but if they are a far percentage off of each other the car will surge a little/lot at times and fuel trims will act a little weird

white2001s10

iTrader: (4)

Yes.
It's an area of your VE table that you go through while getting to WOT.
The values in that area of the VE table are too small by at least 25%, and that's why you're getting those positive fuel trims. It's not a problem with your PE settings.
Once you get the VE values increased in the right area, you will no longer have positive fuel trims there. If you eventually get to negative fuel trims like -1 or -2 that's great and they will not be applied at WOT.

racecar

Thanks for the good explanation. I can believe that with my CNC heads and cam that I need to add more to the VE table, but where?
I may try the SD tune again. I just can't get it to run or idle. I have collected LTFT data and made changes, but it runs worse. Is there any other way to determine where and how much to change the VE table???

white2001s10

iTrader: (4)

Use a wideband instead of narrowband O2's.
Using EFIlive, when you are looking back through your data-logs it will show you exactly where you are in the VE table. That helps a lot.

If you don't have that option, then simply record your MAP & RPM output in your datalogs. Then just backtrack to see where you were in the VE table.

racecar

-UPDATE- I tried setting the PE and the OLFA exactly the same, and pretty much flat line at 1.05. RedHardSupra convinced me to reset my IFR using the Sticky chart and 43.5 psi for the SVO injectors. I also copied the Primary VE to the Secondary. Went for a run last night, I'm seeing better numbers than ever before. I'm cruising at 13.8-14.0AFR and WOT is 12.4-12.6. LTFT are only going to +7 at WOT. There is still room for improvement, but now we have a good baseline to work from. The only place that I'm seeing the LTFT maxed is at decel. Thanks to everyone for the great input and ideas. Thanks white2001 for the clear explanations. I'm going to work on the VE table. More after some runs today.

racecar

OK Team, here is the latest. I worked on my VE table by hand to add to the 3000-4000 column at high MAP. That seems to be where I am at when I go to WOT and experience high LTFT. I lowered the VE at MAP15-20 3000-7000 to help keep the LTFT down at decel. Cruised for 30 min then found some open road on Sunday morning for some WOT runs. AFR is 12.7 at WOT 3000-5000 then starts to richen to 12.2 at 6500. My PE and OLFA are both set flat at 1.05 so I can add some fuel at high rpm to fine tune that. The lower VE numbers at low MAP seem to be lowering the LTFT on decel, sometimes 4-6, still 25 on a few. LTFT at WOT is 2-6. We are making progress. At least I am seeing logical results from the changes in the tune.
PS. I worked for hours to hand smooth the VE table. Is there any better way than clicking on those little lines and dragging them into parallel rows??

jimmyblue

iTrader: (11)

There is an automatic smoothing function but I
still prefer to do it myself; the smoothing will as
happily drag down good (i.e. matching the real
data) cells, as lifting up bad. Manual is also the
only way to push in extrapolations, from the data
you have to regions where you don't.

The decel action, you may have to raise the
minimum airflow while rolling (throttle cracker
and follower) and decrease the minimum injector
pulse width. If you are getting into the DFCO
(deceleration fuel cut-off) then fuel cut will be
dead lean, and trim high. If you disable it there
is some fuel economy reduction and you may
have a rich error instead, if you have the throttle
closing fully and too fat a minimum injector pulse
width. If you prop up the airflow to where the
min injector PW is going to produce a sensible
fueling, but still get some engine braking, that's
where you want to be. There is some lower bound
to min PW, a PCM minimum emitted pulse, but I
don't know what it is. You'd like it to be scaled by
about the same, but inverse factor as you scaled
the flow table. But only if you are actually seeing
the fueling peg onto the min PW in the logs, and
"stuck" negative trims in low-airflow cells.

Judging from the results you still have either airflow
or fuel delivery inaccuracies in the tune because
your WOT results are well richer than the commanded
'EQ ratio / AFR. But you have to factor in the 1+LTFT/100
multipler there, to judge the fidelity really.