LTFT Changing with RPM and Load?

[kmandevi]

Hey, I'm having a remote tuner tune my solstice gxp (LNF) and they said that there must be a hardware issue with my car because my LTFT are stuck at 14.1% in my attached log. I thought the LTFT should settle down at one number, not change constantly, the STFT are the one that changes. Is that right?

Response from the tuner after reviewing the log:
"How does the car feel when you drive it? your MAF vs LTFT is stuck at 14.1 and does not move which concerns us... We are going to give you a remedial tune to see if we can bring this under control before we ramp up the power on the car... I'll send the file over today."

I reset the fuel trims today and drove 70 miles and they are back to 14.1%. I cannot find any vacuum leaks, and no boost leaks noticed in the log. Any ideas? Does this tuner know what he is doing?

Thanks for the help!

[salvadorz24]

A Cold air intake can cause the problem you are describing at least in my car it did. I started to experience really high stuck LTFT After I installed my CAI, but the problem went away after I recalibrated the MAF.

[kmandevi]

Ok, that makes sense. I have an intake filter, charge tubes and high flow down pipe on the car. What I ended up doing was clearing the trims then recording a log before they got to the 14.1 stuck value.

[ZeroBoostBuick]

Your log shows a max of 29'ish psi of boost, and at the same time the MAF shows 23'ish lb/min flow.

I'm not expert, but at almost 30 psi of boost shouldn't the MAF flow be much higher than 23 lb/min ? Correlating with what salvadorz24 was hinting at, about MAF calibration.

[kmandevi]

I think that boost is relative. So it is only about 16 psi over atmosphere. I think you are all correct about the MAF calibration being off, I just expected the tuner to know this because I purchased a stage kit from him which included a intake, charge piping, down pipe and the tune.

[cobaltssoverbooster]

i can make a kit with a tune but depending on elevation, air quality, and fuel quality....ignoring the fact that every engine breathes a little differently even with the same configuration of parts... i would expect the maf to be off.
you should always assume a canned tune will be wrong until a log tells you otherwise.

[salvadorz24]

Can you upload a copy of your tune and a new log

[salvadorz24]

Your MAF really needs to be recalibrated or maybe just clean the MAF or/and replace the air filter.

Who tune the car?

http://s323.photobucket.com/user/cha...a/Maf.png.html

[kmandevi]

After the tuner re-calibrated the MAF everything seems to be back to normal now. Only issue seems to be that my 120k mile turbo is flowing about 3 lb/hr less than it should.

Attached is my latest log.Ken M stage 2 rev 2.hpl

[salvadorz24]

Your fuel trims look better, but you are lean at WOT. We can't help you without a copy of your tune file.

[ZeroBoostBuick]

At WOT your wideband is showing 13.5 to 12.5 afr.. A little lean in my opinion. I would adjust it to have around 11.8 afr (0.8 Lambda).

[cobaltssoverbooster]

Lnf runs 12.6-12.9 under full boost.
Those numbers are normal

[cobaltssoverbooster]

I would fix anything leaner than 12.9 though

[salvadorz24]

At Wot your lambda values range from 1.06-1.12, your target should be around .88-.90

[ZeroBoostBuick]

At Wot your lambda values range from 1.06-1.12, your target should be around .88-.90

1.06-1.12 are EQ values. 14.7 div/1.12 = 13.125 afr

[ZeroBoostBuick]

I gotta say tho, you have almost zero knock at WOT, so that part looks good.

[salvadorz24]

1.06-1.12 are EQ values. 14.7 div/1.12 = 13.125 afr

Sorry but a 1.12 Lamda equals ~16.464 (anything above 14.7 is lean)

It is easier to work with lambda, fuel ratios vary depending on the ethanol content in gasoline, fuel type, etc.

[cobaltssoverbooster]

eq ratio values are multipliers.... 14.7*.86= ~12.6 and as mentioned 14.7*1.12 ~16.46
salvador is correct here.

[ZeroBoostBuick]

EQ Ratio is NOT lambda.

With EQ ratios ...
higher than 1 = richer
lower than 1 = leaner.
-------------------------------------

Copied the following straight from VCM EDITOR from a 2014 Buick Verano 2.4L tune....

"[ECM] 12400 - Power Enrich EQ Ratio vs. RPM: This is the main table that is used to tune WOT fuel. The values in this table are Fuel/Air multipliers (or Equivalence Ratio) ie. values greater than 1 are richer, values less than one are leaner. The values relate directly to the Stoich AFR and the resulting commanded AFR is Stoich divided by this PE multiplier. Eg. if the multiplier is 1.1 then the commanded AFR will be 14.7/1.1 or 13.36.
Lambda is the Opposite of EQ"

[cobaltssoverbooster]

in the lnf they don't work that way
if you have an lnf test it out you will see real fast that the commanded jumps in reverse.
if we were talking about an lsj, ls, 3800, or any newer than 2012 ecotec I would agree, but he has stated this is a Pontiac solstice lnf build. you have the wrong vehicle file your looking at buddy. the lnf is only offered between 2007-2009/10. and is an E69 ecu model.

if kman could post his tune file instead of only logs then we can discuss this over the exact vehicle file that is in question. According to his log file title he has a 2007 Pontiac Soltice GXP...use the repository and check for yourself.
Bone Stock GMPerformance Power Enrichment Table for E69 LNF ECU
Capture1.PNG