Please help me understand something here...

[ACP TED]

OK, I know this may sound like "dumb question", but... You don't know if you don't ask, right?

Anyway, I picked up a new Trinity a few weeks ago and I'm lovin' it. I have been reading everything I can find on using it properly, but... I'm thinking I may be confused on LTFT adjustment.

I'm using DSLogRedux to view and analyze the logs and putting 100+ miles on between adjustments recommended by DSLogRedux. Now, with my second log, again its tellin' me to add (+8) to the LTFT...

With this second log, I'm seeing LTFT average of -8.65%... So, my question is... Am I correct in thinking that -8.65% means I'm running rich?

With my research, I read that "adding" to a negative number is telling PCM there are larger injectors installed and to spray less fuel, etc etc... So in my mind that's leaning the mix...

The bottom line here is, the second log has a much wider LTFT range after the first adjustment, which with this log, it shows a min of -28.13% and max of -2.344%.

So, I have made the recommended +8% adjustment to the LTFT and need to drive some miles, then I'll pull another log...

Oh, as an FYI... DSLogRedux shows 'no data' for LTFT2 which I only have one 'pre-cat' O2 sensor, I think this is correct too.

Thanks in advance for constructive input on this post.

[ACP TED]

hmmm... maybe i understand more than i thought?

[06MonteSS]

negative ltft's mean you're on the rich side, so the ecm is subtracting fuel..

positive ltft's mean you're on the lean side, and the ecm is adding fuel..

and remember, ltft's will not always be the same.. they will differ depending on air temp.. and both banks will not always be the same...

and if you are not getting any data for bank 2, then something is wrong with your passenger side front O2 sensor.. because you do have 2 banks on that truck and you should be getting data from both...

also keep in mind, that dslogredux does not take into account the intake air temp.. so if you get it adjusted during an 80-degree day.. then log again when it's 60, or 90, your ltft's will be off compared to the last adjustment, which is normal and is what they're supposed to do.. so don't keep adjusting it like that, you're just chasing your tail.. you would be making adjustments every day lol..

if you want to get things dialed in correctly and gain even better/more performance, consider getting a custom tune done, so the fueling can be adjusted the more correct way via the MAF sensor table.. can get custom tuning done from www.diablewtune.com

[ACP TED]

Thank you! for the reply here...

I am planning on a 'custom tune' eventually... But my thinking is, after I decide on an exhaust setup...

If I may pick your brain once more... The 'Bank 1 & 2' thing... Am I understanding right, that each side of the engine should have a 'pre-cat' O2 sensor? And the 'pre-cat O2's' are reading the A/F ratios? And then two 'after-cat' O2's?

I have looked inside and under, I only see a 'passenger' side 'pre-cat' O2 sensor... Anyway, I was just wondering why DSLogRedux shows no data for 'Bank 2'? And 'Bank 1' does... FYI, I have no 'error codes' showing up.

But anyway, the weather here has been warm and very humid the last couple of weeks and have kept that in mind, and now (the last couple of days, the LTFT's are now 'stable' and looks like it's averaging right around +/- 2%. And from my understanding, this is a good thing.

I know I'm a "newbie" here, but I love this kinda stuff and the Trinity has given me new things to learn... After all, these new engines are WAY different than once upon a time when carburetors and points were the norm. LOL

[06MonteSS]

yes, on that truck, there are 2 front O2 sensors (before the cats), and 2 rear O2 sensors (after the cats).. so yes, there should be 4 sensors total.. 2 in the front - passenger and drivers side.. and 2 in the rear - passenger and drivers side...

[ACP TED]

Well... I guess I better stick my head under that hood a little deeper...

And then figure out what I may have done to get the no data thing...

Hey! Thank you for your time and input here I really appreciated it!

Are you the one to get a hold of a custom tune?

[06MonteSS]

yes I am.. you can email me directly at: diablo DOT help AT gmail DOT com

[ACP TED]

yes, on that truck, there are 2 front O2 sensors (before the cats), and 2 rear O2 sensors (after the cats).. so yes, there should be 4 sensors total.. 2 in the front - passenger and drivers side.. and 2 in the rear - passenger and drivers side...

FOUND IT!... Holly crap, when I said I would have to stick my head in a little further... Crap, GM buried that drivers side O2 sensor. And here I was thinking it would be obvious like on the passenger side. DUH.

With the nice weather we're having here in Michigan (at the moment) the LTFT's are holding well, and the "eyeball averages" are right in the -/+<2... So, now for an exhaust plan.

Thanks again.

[Bigtrucklover]

Not to hijack, but what temperature should we be targeting for ltfts?

It's been high 90s here, so I've been logging in the evening when it's in the low 90s. Average summer high in mid-July is 90. Should I wait for it to cool back into the 80s, or allow a slightly richer ltft value?

[06MonteSS]

if you log and the intake air temp is in the 90's, you want your AVERAGE ltft's to be around -3.xx's usually...

in the mid to upper 80's, you want them around -2.xx's...

70-low 80's, about 0.xx to 1.xx...

[Bigtrucklover]

if you log and the intake air temp is in the 90's, you want your AVERAGE ltft's to be around -3.xx's usually...

in the mid to upper 80's, you want them around -2.xx's...

70-low 80's, about 0.xx to 1.xx...

So when you say intake air temp, I should be going by the IAT temp on the Trinity, not actual outside ambient? <Edit: I see I can log ambient air temps on the Trinity as well. It reads about the same as the truck's DIC>

Just want to be sure because, after the car was fully warm today, the IAT gauge was reading 35C (95F), while the Ambient gauge listed 86F. Nearly a 10 degree difference!

Thanks.

[06MonteSS]

yes, you need to go by the INTAKE AIR TEMP, since that's the actual temp of the air going into the engine/intake... don't care about outside ambient temp...

[Mike_Levy]

IATs will always be warmer than ambient. The idea is to get them as close to each other as possible. 10 degrees isn't bad at all. Log it in traffic and you'll see IATs get 60-70 degrees above ambient or more.

[ACP TED]

How 'bout a new lesson here...

Now that my LTFT's are looking good here, and the temps have been in the mid to upper 70's and my truck is hanging out in the "0.00's" starting around 1200 rpm's and up...

So I'm now wondering how the "PE" comes in to play? My truck seems to be hanging out around the 14's and have read somewhere, where the "12's" is where one wants to target.

Any thought's here?

Thanks in advance...