Luigi Noschese

Hello

I am a little bit confused about the fuel trims on a ESL ecu.
My car is a 95 gt.
If the trim value is higher then 100 does that mean its to lean in those cells or is it to rich?

ossett2k2

iTrader: (9)

High numbers in fuel trim means it's adding fuel,so your lean in those areas of the map.

bludgod

iTrader: (3)

though it does not necessarily mean you are lean, it means the ECU has to add a little fuel in that region compared to what your maf/fuel table is asking for to reach target AFR. So long as the trims aren't too extreme I wouldn't be getting up in knots over it as the values will move around as the weather changes.

ossett2k2

iTrader: (9)

Yeh with the trim table at 112 then the o2 sensor is doing its job,but the fuel map figures are lean is what I was saying.
As bludgod says it's not too extreme,I personally would want to get them closer to 100 but you're best turning off closed loop to do this(although you can't on the early ESL)

ossett2k2

iTrader: (9)

Would be interested to know if the figure of 112 means the fuel table or maf table is out by 12% or is this figure of 112 not a percentage?

Are the trim tables in newage cars or different ECUs like alcatek pretty much the same as ESL?

bludgod

iTrader: (3)

as far as I know on a newage car the fuel trim value is an adjustment to the MAF g/s reading to get the o2 sensor reading back to what the fuel table is asking for.

So say you had 10% adjustment then it's the MAF reading +10% is what's needed to get the fuel reading to be 14.7 again (assuming that's what's being asked for in the fuel table). So the fuel table is the target, and the o2 swing is used to decide how far out the maf reading is vs actual amount of air consumed.

The Rig

iTrader: (13)

I spent a wee while messing with fuel trims and can confirm, they change with the wind lol

I found that, disconnecting 02 gave me my raw AFR on the gauge, even tho say i had 14.7 around the low load points in the fuel table my actual reading was 12.

So id amend my injector scale to get the actual reading as close to the fuel table, great so far.

reconnect 02, fuel trims come in line a bit better , good stuff.

So, onto the areas outside of 02 control and the fuel table/wideband readings didnt quite line up, not majorly but enough to be out , so i then found i had to adjust injector scale to suit the WOT areas (as this is where we drive mostly ) , so my fuel trims then went out of whack again

So, let the 02 do its job is my thinking now

bludgod

iTrader: (3)

yup - let the o2 do it's job unless you've drastically changed the setup (mafless setup or a massively massive intake pipe on a MAF setup) then you shouldn't need to tinker too much with things. Just play with the injector scale until on boost fuel is steady and work from there.

if your MAF based then you do have the option of rescaling the MAF sensor to get the fuel trims and the target AFR a lot more accurate, but so long as the wideband reads the figure you want then don't get hung up on what the table says exactly or you'll be so far down the rabbit hole of MAF scaling you'll forget why you were doing it in the first place

The Rig

iTrader: (13)

Heres a question on fuel trims then

I have 2 maps, when i was messing with fuel trims, one gives me corrections of between negative 6 and negative 11% corrections, so cells populated with between 88 and 96 (reducing fuel as running rich)

The other gives me positive corrections of between 1 and 4% , so cells populated between 101 and 104 ( so running slightly leaner)

It was hard to get an inbetween of the 2 maps as i have had to adjust the MAF calibration, these 2 maps were the closest i could get to minimal fuel trim adjustments


So, which one is best to use or doesnt it matter, i mean , both result in the stoich being reached i guess ?

ossett2k2

iTrader: (9)

Which ever map is the best I guess.
The one with 1-4% adjustment sounds better.
How come you were swapping between maps?

Fuel trims are shared and don't have separate tables for map 1&2

The Rig

iTrader: (13)

Sorry, worded badly.

I created 2 Maps, both the same with all other settings just differnt AFR`s at low loads to affect fuel trims, when i was messing about trying to get a nice looking fuel trim table.

the one with leaner AFR`s obviously gives me the one with postive trims, 101 - 104`s , the other with fuel table AFR`s that bit richer gives me the negative fuel trims 88-96.

Just out of curisosity i was thinking if either was a better setup or does it matter as either way, positive or negative stoich at closed loop is achieved ( altho with negative trims if 02 failed id run rich rather than lean....... )


I also have the maps set to reset fuel trims/kock control if i go between map 1 or 2 but thats another matter


cheers

ossett2k2

iTrader: (9)

Don't suppose it matters as like you say,the ECU will always target 14.7
I just prefer my tables like I prefer the missus,nice neat trims

I switch off my reset between maps but I also have my reasons

The Rig

iTrader: (13)

Yeah , think I will run the positive one as its only adding 1 to 4 % fuel yet the negative one is removing like 11% in some places

Cheers bud