Long Term Fuel ignores Closed Loop ECT Lockout?

[jdniss]

Hi,

Unsure if this is intentional or not - is the Long Term Fuel Trim table supposed to ignore the Closed Loop Lockout parameters it's based on?

I've only just enabled LTFT and found that below the CLL ECT lockout, LTFT table values are being applied - it's effectively fighting against the Warm Up Enrichment values until the CLL lockout value is exceeded.

Or is there a setting I've missed?

PC Link G5 v7.2.3411 on G4X



Thanks

[jdniss]

Noticed this morning LTFT ignores the Startup Lockout that CLL abides by as well.

The only way I can think of configuring the same lockout, is via a Virtual AUX bound to a GP Output with applicable conditions..
Though this is a waste of either input/output, to then lock out a trim that should internally handled within the CLL / LTFT function.
 

In an extreme case; if the VE map was so bad that LTFT was allowed to pull 40% and save the values - by the time the vehicle was started again you have a scenario where the LTFT pulls so much fuel prior to warm-up or CLL lockouts, that the vehicle would barely idle.
Haltech gets around this with a "Long Term Trim Minimum Temperature" option.




Similarly during a "sensor failure" - unplugging the Lambda sensor - CLL is disabled, however LTFT values are still applied in the G5 software.
Looking at Haltech NSP again, Haltech workaround this issue with a "Long Term Fuel Trim Rich Bias" that allows a richer target than the current configured Target AFR - in the event the CLL/LTFT system fails.

Hopefully some of these options can be considered for a later version of the G5 Firmware.

Thanks.

[dx4picco]

if your engine has a LTT of let's say -10%, that would mean that in that particular cell which is not that well tuned, the engine needs 10% less VE to run stoïch. 

Now why would you need to disable that, even on startup?

saying that it is counteracting your cold start enrichment is also weird, and would rather lead to change cold start parameter, because actually tuning the VE cell will require that anyway

[Adamw]

This is intentional as dx4picco suggests.  LTFT will not be "learning" when CLL is disabled, but the learned trim from the table will always be applied.  There is a "disable input" in the LTFT settings that you can use to disable both learning and the trim under any conditions you think it is not wanted.  

[jdniss]

22 hours ago, dx4picco said:

if your engine has a LTT of let's say -10%, that would mean that in that particular cell which is not that well tuned, the engine needs 10% less VE to run stoïch. 

Now why would you need to disable that, even on startup?

saying that it is counteracting your cold start enrichment is also weird, and would rather lead to change cold start parameter, because actually tuning the VE cell will require that anyway

The engine was at operating temperature once CLL enabled and started incrementing values into the LTFT table.

If LTFT values can only be populated via enabled CLL trim - presumably once the engine is up to operating temperature and warmup has decayed away - it's counter productive to pull warmup fuel via LTFT even before CLL is enabled, as the help file leans toward.

Warmup is tuned, that isn't the issue - LTFT being enabled by default regardless of ECT, unless locked out - is.

 

17 hours ago, Adamw said:

This is intentional as dx4picco suggests.

Thanks for confirming.
I suspect these LTFT 'Disable Input' parameters below will mimic the CLL lockout parameters?

Is there any way to directly link a GP Output to LTFT 'Disable Input'? - I can't select one from the list..
Or do I have to go via a Virtual AUX as below?

Thanks

[Confused]

Your Warmup may well be "tuned" - but it's "tuned" based on the operating temperature fuelling table - which CLL and LTFT are indicating are incorrect.

So - with CLL and LTFT Learning enabled, you are slowly correcting your underlying fuelling table.

Remember that the Warmup stuff is making modifications on top of the underlying fuel calculations from the fuel table - you've baked in errors here - so your now "tuned" warmup needs re-tuning based upon the corrected values in the main fuelling tables.