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View Full Version : Fuel trims and different type of fuel



lateshow
04-06-2012, 09:41 AM
Ok. I have noticed the followin: High and Medium fuel trims are not working? 0 all the time.

Low fuel trim seems to works, BUT, all cars I have logged in Finland show the same value 4,6875. Today i just made my ecu use the closed loop again and i could see as the value climbed to 4,6875 when idling in closed loop. But why is that? Shouldnt we get the value around zero, and the value doesn't update afterwards, stays on the same spot. This suggests that our fuel contains so much alcolhol (should be 5% max) that the trim goes too high, and it doesnt show anything after 4,6875. The value just clips there? In evos the values can go higher?

What do you get as fuel trim low in your uk cars and nz and au cars?

lateshow
06-06-2012, 03:21 PM
Please lads share me your low trims? You gotta know where they lie?

BCX
07-06-2012, 07:03 AM
Ok. I have noticed the followin: High and Medium fuel trims are not working? 0 all the time.

Dont think our ROMs uses these... I believe the code might he there though...

Kenneth
07-06-2012, 07:03 AM
Only Low fuel trims are actually used.

What MUT references are you logging and what addresses are at those references in the MUT table?

/edit: checked and Bill is right, only low fuel trim is used

lateshow
07-06-2012, 11:19 AM
Well what values do you have in your low trims? With standard injecetors and standard scaling. Ive multiplied my scaling by 0.95 and still the same 4,68...

swinks
05-07-2013, 06:24 PM
Thread from dead. Did few runs after setting up tps and ifs.
Getting fuel trim value 4.8 regardless. Air leak or that's how ecu maps are set?

lateshow
08-07-2013, 07:14 PM
Like i've said here in many places, with standard scaling it goes up to 4,8 and stays there. If you reset your ecu you can see that it's 0 and you get a big positive oxygen feedback. Then drive a little and stop to idle. The trim maxxes out and you get a little smaller but still positive oxygen feedback.

BUT

There seems to be some reason in this. If you rescale it so that you get something else, like +- 0 trim, the car feels a lot lazier as the AFRs dip very easily below 12.

Kenneth
08-07-2013, 11:19 PM
Have you tried reducing the injector latency a little rather than re-scaling the injectors?

With the ID1000 injectors my car is running very well with the fuel trims within limits. I don't see less that 12:1 unless on full chat and then usually around 11.2:1 to 11:1

The trick is to balance the injector latency and the scaling. When at idle, the latency is the #1 contributor to AFR values

fassi1
08-07-2013, 11:55 PM
By lowering injector scaling, duty cycle map is increased. By doing this in closed loop long term fuel trim is reduced but open loop becomes overfueled in comparison to situation befor rescaling injectors and for that reason open loop needs some adjustments.

swinks
09-07-2013, 07:56 AM
Actually didn't follow this with stock injector, because few days back I swapped them for 560cc anyway.

lateshow
11-07-2013, 10:41 AM
Tried a bit to mess with the latecy but had no effect. With ethanol that isn't such a big problem since it needs more fuel all the time.

One idea would be to mess with MAF smoothing at lower Hz.

It just feels bit strange that these are designed as stock to be like this. In evo V and so on the trims are working. I've seen one vr4 legnum that had a live low fuel trim as standard. Weird.