Ludikraut

iTrader: (17)

Did some logging last night, trying to see where my fuel trims are at after the injector rescaling efforts of the past week.

Here's what I've got so far, on back-to-back OBD-II and Evoscan sessions, I recorded the following values:

Dynoscan (OBD-II) ... Evoscan (MUT-III)
-----------------------------------------------------
5.50% LTFT ... 124.2188 FuelTrim_Middle
2.30% LTFT ... 110.9375 FuelTrim_Middle
4.70% LTFT ... 117.1875 FuelTrim_Middle

That leaves me with a formula of:

LTFT = ( FuelTrim_Middle - 100 ) / (x)

where x is between 3.6 and 4.7.

I will do more logging when I drive the car around some more. If anyone can log some more OBD-II and Evoscan numbers, maybe we can come up with a constant for (x) ...

l8r)

AMS

iTrader: (3)

Have you noticed that idle fueling is not affected by fuel map values?

Ludikraut

iTrader: (17)

To be honest, my idle is so erratic that I'm having a very hard time tracking any kind of trends. Usually it hovers just below 14.7, but then it'll jump to 16.8 and immediately nosedive to 12 or less or vice-versa. It seems like it's a little on the lean side, since LTFTs slowly go up at idle. Once I'm confident in/happy with the overall injector scaling, I will start playing with the injector latency settings at 14V.

l8r)

l2r99gst

iTrader: (2)

Martin,

Well, it shouldn't, as long as you're in closed loop. The maps are open-loop fueling, correct?


Eric

MalibuJack

iTrader: (5)

In closed loop the low load portions of the fuel map have no affect other than to make adjustments to get your fuel trims closer to 0...

The good news is, if you can get those fuel trims real close to zero, the car will cold start perfectly.. But otherwise you'd have to disconnect the O2 sensor to keep it from going into closed loop to alter that portion of the fuel table.


But I thought I was the only one.. Not only that, my fuel trims never seem to change, at least all that frequently.. And I really doubt my closed loop adjustments are so close to perfect that they don't need any trimming at the moment..

Anyone think maybe those fuel trim values aren't updated very frequently.. One of mine is always at 100%, another is around 50%, and the third is always at 113.. Never seems to change though...

l2r99gst

iTrader: (2)

It takes a bit of time for them to adjust. The idle one, if adjustment is needed, should start to move after a few minutes of just idle. Cruise will adjust after a good 5-10 minutes of steady cruise.

Just look at your STFT....that will tell you if your LTFT needs adjusting. It may just not have time to do it, depending on how you are driving.

Eric

Ludikraut

iTrader: (17)

They can update quite frequently and at other times stagnate. I can send you a couple of logs of city driving and hwy cruising if you want to see the intervals...

l8r)

MalibuJack

iTrader: (5)

I guess its possible that my trims are close enough that they may not update frequently, I just didn't think that was actually possible.

fsugatorbait

iTrader: (16)

On all of my logs, granted there havent been many, but all three trims stay at 100. Curious to know if that is good or bad?

MalibuJack

iTrader: (5)

See, thats kinda what I see, at least one of those trims stays at 100 all the time, the others are somewhere over 50 and the other is 115 or so.. And rarely change..

I guess my point was it doesnt clearly show STFT and LTFT's like a regular OBD-II scanner so I'm having some difficulty getting my head around it.. At least if it never appears to change when I'm trying to make change..

Ludikraut

iTrader: (17)

More log info:

Dynoscan (OBD-II) ... Evoscan (MUT-III)
-----------------------------------------------------
12.50% LTFT ... 150.00 FuelTrim_Middle
12.50% LTFT ... 150.00 FuelTrim_Middle
9.40% LTFT ... 139 FuelTrim_Middle
9.40% LTFT ... 139 FuelTrim_Middle
9.40% LTFT ... 137.5 FuelTrim_Middle
9.40% LTFT ... 137.5 FuelTrim_Middle

Looks like the multiplier hovers around 4. This set of data was taken by me switching between Evoscan and Dynoscan as fast as I could (maybe 30 seconds to switch) over approximately an hour's worth of putzing around town, running errands.

So for now I will assume the equation to be:

LTFT = ( FuelTrim_Middle - 100 ) / 4

Overall the FuelTrim_Middle stayed very consistent with the LTFT readings I was getting.

l8r)

hondafan

iTrader: (25)

i just installed one of al's base maps and my LTFT idleing is around -5, cruising around -11(on an OBD2 logger). does this sound far off from what i should be seeing? i asked al about it but didn't get an answer yet. are - leaning out or richening?

l2r99gst

iTrader: (2)

A negative value means the ECU is taking out fuel to maintain a stoich ratio. So, that means that your injectors or latency (or combination of both) should be adjusted to take out fuel.

Eric

MalibuJack

iTrader: (5)

Anything around 10% or less (plus or minus) is a good target and will generally run correctly.. The closer you can get to zero the better, but the base map is doing a very good job with it being that close..

Since there is a discrepency of -5 and -11, you can increase the injector latency slightly, it should get you real close (a small amount at a time) In one of the other posts it explains how latency can affect the cruise and idle and its trims.. It turns out that after monitoring the data, that the accel enrichment value may actually be a contributor also.

When I was logging data, what I noticed was the Accel enrichment would tend to tip-in on acceleration, but hover afterwards.. Let me know if you guys also see that.. since that can explain a few things I had seen..

hondafan

iTrader: (25)

and changing the injector latency has no effect on full throttle operation correct? it will only get me closer to the target LTFT of 0? by slight increase, what are we talking, i'm new to this.