Ltft and Stft different on each bank

Theador · 07-23-2016, 02:53 AM

I've been monitoring my fuel trims which are generally hovering around 0 now or going into negative, however my bank1 side is always 2-3% lower than bank 2. Surely they should both be the same?

ferocity02 · 07-23-2016, 05:55 PM

Ideally they would be the same, but the injectors aren't perfect. A couple percent difference is pretty reasonable.

titium · 07-24-2016, 04:44 AM

all the same index? if new ones were installed were they coded?

I honestly wouldnt worry until they start getting into double digits. couple of % is pretty normal.

in an ideal world the fuel trims would be 0 all the time. fuel trims are there to compensate for non perfect parts of the system, errors in intake air quantity measurement, injectors and injector aging, unequal airflow distribution between cylinders, fuel quality ect ect. of which all of these are perfectly normal.

135Pats · 07-24-2016, 10:21 AM

I wouldn't get too hung up over a delta like that between banks. If one was pegging STFTs and another was pulling fuel, then sure you'd have an issue to track down. This to me is more a reflection of the injectors not being literally 100% identical.

You are fine.

Theador · 07-24-2016, 11:41 AM

Thanks guys.

ferocity02 · 07-24-2016, 12:43 PM

Just to add more to this thread, the LTFT difference between banks can indicate a potential issue. For example, when my #6 injector was leaking, my bank 2 LTFT was typically 15-25% lower than bank 1 under idle and normal cruising conditions.

A difference of a couple percent is normal. After replacing all injectors I'm still seeing differences of 1-3%.

raffi007 · 02-15-2020, 01:55 PM

Quote:

Originally Posted by ferocity02

Just to add more to this thread, the LTFT difference between banks can indicate a potential issue. For example, when my #6 injector was leaking, my bank 2 LTFT was typically 15-25% lower than bank 1 under idle and normal cruising conditions.

A difference of a couple percent is normal. After replacing all injectors I'm still seeing differences of 1-3%.

What do you make of my reading ?
LTFT on bank 1 : 0.3
LTFT on bank 2 : 5.2

335e92tx · 02-24-2020, 04:16 PM

Quote:

Originally Posted by raffi007

What do you make of my reading ?
LTFT on bank 1 : 0.3
LTFT on bank 2 : 5.2

can you log it for about a 10 sec cruise and also idle?

How are warm and cold starts? Rough?

07-23-2016, 02:53 AM	#1
Theador Lieutenant 83 Rep 369 Posts Drives: BMW E91 M Sport 335i Join Date: Nov 2013 Location: Henley on Thames iTrader: (0)	Ltft and Stft different on each bank I've been monitoring my fuel trims which are generally hovering around 0 now or going into negative, however my bank1 side is always 2-3% lower than bank 2. Surely they should both be the same? __________________ e91 335i MSPort 6MT \| MHD Stage 2 +FMIC v7.1 \| VRSF Catless DPs \| Hartge ARBs \| Quaife LSD \| Eibach Springs \| 313 Alloys \| VRSF 7" Intercooler and Ingen Intake
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07-23-2016, 05:55 PM	#2
ferocity02 Colonel 530 Rep 2,083 Posts Drives: 2013 135is Join Date: May 2014 Location: USA iTrader: (8)	Ideally they would be the same, but the injectors aren't perfect. A couple percent difference is pretty reasonable.
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07-24-2016, 04:44 AM	#3
titium Major 327 Rep 960 Posts Drives: 2009 BMW 135i Join Date: Jun 2015 Location: Sydney iTrader: (0)	all the same index? if new ones were installed were they coded? I honestly wouldnt worry until they start getting into double digits. couple of % is pretty normal. in an ideal world the fuel trims would be 0 all the time. fuel trims are there to compensate for non perfect parts of the system, errors in intake air quantity measurement, injectors and injector aging, unequal airflow distribution between cylinders, fuel quality ect ect. of which all of these are perfectly normal.
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07-24-2016, 10:21 AM	#4
135Pats Major General 456 Rep 6,478 Posts Drives: A few BMWs Join Date: May 2012 Location: Maryland iTrader: (3)	I wouldn't get too hung up over a delta like that between banks. If one was pegging STFTs and another was pulling fuel, then sure you'd have an issue to track down. This to me is more a reflection of the injectors not being literally 100% identical. You are fine. __________________ E88 N54 Alpinweiss/Coral Red/Motiv HTA 3586r Tial .82AR/Other stuff...652WHP F30 N55 XDrive EBII
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07-24-2016, 11:41 AM	#5
Theador Lieutenant 83 Rep 369 Posts Drives: BMW E91 M Sport 335i Join Date: Nov 2013 Location: Henley on Thames iTrader: (0)	Thanks guys.
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07-24-2016, 12:43 PM	#6
ferocity02 Colonel 530 Rep 2,083 Posts Drives: 2013 135is Join Date: May 2014 Location: USA iTrader: (8)	Just to add more to this thread, the LTFT difference between banks can indicate a potential issue. For example, when my #6 injector was leaking, my bank 2 LTFT was typically 15-25% lower than bank 1 under idle and normal cruising conditions. A difference of a couple percent is normal. After replacing all injectors I'm still seeing differences of 1-3%. __________________ 2013 135is DCT Carbon Black Metallic
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