swarthyfellow

Its hard to say it was a few months ago i tuned it... roughly 1500 miles. I could remember if i had my laptop with and could pull up the program. Why doesn't special forces show the timing a fuel changes when the tune is reopened anyway. But wouldn't that affect both banks equally?

tbirdscwd

I don't see how it would affect the two banks unevenly, but I am by no means an expert in the fuel trim category. I know Cliffy has a program that keeps track of all the changes you make for each tune. http://paladinmicro.com/PalMFrame00.htm?wks=sf2

cliffyk

When SF was designed there was a liability concern about persisting the fine tuning settings and it was determined that they would not be saved.

My SFScrape program lets you document your tunes, and can save and restore (there's a "Warning" dialog that you must agree to before the settings will be restored) the settings that SF does not.

It appears you have SF v1x, you can download SFScrape here.

The changes made to the tune affect both banks, however for a whole lot of reasons that would take a semester for me to teach the banks do not track one another precisely (this is in large part because of differences in the O2 sensor's feedback).

Depending on how far and how often you drive it could take 1500 miles for the adaptive learning algorithms to complete their cycle, especially if you did not clear the KAM when you flashed the modified tune (it helps to disconnect the battery for 5-7 minutes when you load a tune in which fueling setting have been changed).

In the last, do you have a wideband O2 system? If not you should not be messing with the fueling settings at all.

If you like send me your stock tune (from the Original Files folder), and the .pcm and .txt files for the tune you are running--I can look at it in Commando and see what selections you made in the fine tuning dialog.

cliffyk@paladinmicro.com

swarthyfellow

Well I am pretty sure that i have an exhaust leak on the side it has been quite a bit latter. I would image that that would affect the o2 sensors. But i have bigger issues now, i have a leaking heater core. I did get that software working too. thanks. I don't have a wide band sensor, which is why i never really change the fuel trims much. I just leaned it out in the low rpm range due the fact that i would smell of gas if not. It has been a pretty rough week in school so i didn't get any actual work done. I'm hoping to get out tomorrow and check everything and do my oil change.

swarthyfellow

Ok so to bring this back to the table... I have fixed the exhaust leak and i have set my fuel trims to normal. I went out and pulled some data and it appears that my fuel trims are level under any kinda of engine load (both short and long) but at idle the one bank is still higher then the other? Any thoughts?

cliffyk

Perfectly normal, as are differing O2 sensor switching frequencies from bank-to-bank at idle.

The closed loop fuel trim calculations s for each bank are fully independent, and at idle airflow through the manifold, pressure drop across the injectors, relative response of each bank's O2 sensor, and a number of other factors, differ--"favouring" one bank or the other--slowly and significantly enough for the independently calculated trims to be visibly different.

As engine speed increases the bank-to-bank variances level off and the calculated trims become more in line with one another. What you are seeing is the PCM doing it's job, maintaining each bank's AFR at an average of 14.7:1, regardless of the bank-to-bank differences in input parameters.

swarthyfellow

thats what i was hoping you would say. I was pretty sure that it was normal. I was thinking that since one side has the EGR and the other doesn't it could make a difference in the trims at idle but not under load due to high flow rates. How much to u think that plays a roll in the trims, if any?

cliffyk

Good thought, however, from the shop manual:
Also per "the book", the EGR is only active at "moderate load and rpm" (MLR). As emission thingys go the EGR is rather benign, the introduction of ABB ("Already Been Burned") gases at MLR¹ actually reduces combustion chamber temperatures and allows the PCM to advance the timing a bit. This provides improved fuel economy.

That said, the EGR valve on my '03 was sticking and making the engine stumble a bit at at light loads--being lazy and cheap (and having broken off more than one EGR pipe in my life) I just disabled EGR in the tune. This cost me about 1/5 MPG on the highway, not enough to worry about.

---------------------------------------------------
¹ - Think cruising in 5th on the highway.

swarthyfellow

hmm that is yet again something i didn't know and now i do. great info as usual, thanks

swarthyfellow

I have another question regarding fuel trims. Is it always trimming up and down from from 14.7. Really my question is how accurate is using (MAF/(Air/fuel))/(#injectors*injector flowrate*80%) to calculate injector flow percentage and fuel flow rates and Why doesn't Recon show it for my 96?