Quick question about LTFTs updating past 4k rpm
10-24-2013, 01:28 AM
#1
Quick question about LTFTs updating past 4k rpm So I took the throttle body off and started tuning the 99 ws6 in SD. I've been tuning part throttle up to 4k rpm using the LTFTs and pretty much done and it runs so much better now.
Then I started to tune WOT and noticed that the fuel trims are still changing so question is, why is the fuel trims updating at WOT? I'm pretty sure at WOT its supposed to go into open loop right? And I'm trying to adjust the power enrichment tables but with the LTFTs still learning then wont that throw everything off as it learns and changes the fuel trims? Do I have to wait for the trims to finish learning all the way up to redline before I can start messing with the power enrichment tables?
Then I started to tune WOT and noticed that the fuel trims are still changing so question is, why is the fuel trims updating at WOT? I'm pretty sure at WOT its supposed to go into open loop right? And I'm trying to adjust the power enrichment tables but with the LTFTs still learning then wont that throw everything off as it learns and changes the fuel trims? Do I have to wait for the trims to finish learning all the way up to redline before I can start messing with the power enrichment tables?
10-25-2013, 03:42 AM
#5
I am using a wide band for wot tuning. And by SD i mean I'm tuning using speed density with map and no longer using the maf.
Ltft is now turned on. Not saying it was updating with it turned off. When i tune wot i turn off ltft, stft, dfco, and of course maf. What I'm saying is now that I'm done, and i have turned ltft back on, i have noticed that it's updating even at wot at all rpms. I thought it's not supposed to
Ltft is now turned on. Not saying it was updating with it turned off. When i tune wot i turn off ltft, stft, dfco, and of course maf. What I'm saying is now that I'm done, and i have turned ltft back on, i have noticed that it's updating even at wot at all rpms. I thought it's not supposed to
10-25-2013, 09:37 AM
#6
My understanding is when you go into wot you go into open loop and your fueling comes from the VE table. If fuel is being added during this time, look at the EQ Ratio. Most people set the eq ratio to 1 in all cells above 176 degrees. This will prevent additional fuel at wot. The LTFT are only used with the narrowband sensors, narrow band sensors are not used at wot, this is why a wide band should be used to calibrate the VE Table at wot.
11-01-2013, 07:43 PM
#7
TECH Senior Member
No, not quite...
With MAF:
when you go WOT, MAF is used to calculate airmass (after the transition), PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
Without MAF:
(should be seeing a MAF DTC, otherwise you're not in SD)
VE is used to calculate airmass always;
when you go WOT, PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
With MAF:
when you go WOT, MAF is used to calculate airmass (after the transition), PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
Without MAF:
(should be seeing a MAF DTC, otherwise you're not in SD)
VE is used to calculate airmass always;
when you go WOT, PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
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11-02-2013, 01:20 AM
#8
I've got everything figured out now. Instead of tuning SD with LTFT's I started tuning idle, part throttle, and WOT with wideband. So much faster and easier. Wish I did that in the first place. And just got back from the track. Went from a 12.7 to 11.8
11-02-2013, 02:50 PM
#10
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With the LTFT on during WOT it will in fact add fuel only to maintain stoich. You need them off when WOT tuning. After tuning I would keep them off and only enable STFTs. Nice time up in Hell Paso. Went to that track a bunch when I lived up there for 2 yrs.
11-02-2013, 05:45 PM
#11
TECH Senior Member
this happens when you're in Closed Loop and some other fueling table activates (e.g. PE activates).
11-03-2013, 09:07 AM
#13
No, not quite...
With MAF:
when you go WOT, MAF is used to calculate airmass (after the transition), PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
Without MAF:
(should be seeing a MAF DTC, otherwise you're not in SD)
VE is used to calculate airmass always;
when you go WOT, PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
With MAF:
when you go WOT, MAF is used to calculate airmass (after the transition), PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
Without MAF:
(should be seeing a MAF DTC, otherwise you're not in SD)
VE is used to calculate airmass always;
when you go WOT, PE should have enabled, and then:
- if OL prior to WOT, then WOT fueling is from the richer cell in PE table or OLFA table;
- if CL prior to WOT, then WOT fueling is from PE table with last LTFT applied (negative LTFT is rounded up to zero).
one thing you are forgetting is that with a MAF... it is commanded to be used according to a variable called "steady state"
steady state is something you can set the parameters of in the tune.
and no matter what...there is a Variable that commands the MAF to be in 100% control after a certain RPM(typically 4000 rpm in the stock LS1 tune)
that variable can be set lower if you want to make the MAF in control full time at a lower rpm...and when you tune the MAF, I like to set it to 400 rpm(lower than my engine will ever see) so its 100% in control and no VE table is used at that point.
the only time 100% MAF control can be removed is if you dont have a MAF or if it has been "Failed" either in the software or mechanically removed.
no matter what..... which ever device you use, at WOT, it will look to see if you have any LTFT recorded for those fuel trim cells(remember...its in FTC, not VE table cells) and it will be carried over into WOT if the value is positive as a precautionary measure.
11-03-2013, 06:44 PM
#14
TECH Senior Member
SE,
lol, ok, I did say "(after the transition)"...
you're right, MAF is increasing as RPM increase, so MAF can't be at steady state.
so, for the discussion, does "steady state" mean which of the following:
- airflow is at steady state (or within the limits of steady state);
- cylinder airmass is at steady state (or almost);
- throttle position is at steady state (or within limits).
lol, ok, I did say "(after the transition)"...
you're right, MAF is increasing as RPM increase, so MAF can't be at steady state.
so, for the discussion, does "steady state" mean which of the following:
- airflow is at steady state (or within the limits of steady state);
- cylinder airmass is at steady state (or almost);
- throttle position is at steady state (or within limits).
Last edited by joecar; 11-03-2013 at 07:13 PM.
11-03-2013, 09:04 PM
#18
SE,
lol, ok, I did say "(after the transition)"...
you're right, MAF is increasing as RPM increase, so MAF can't be at steady state.
so, for the discussion, does "steady state" mean which of the following:
- airflow is at steady state (or within the limits of steady state);
- cylinder airmass is at steady state (or almost);
- throttle position is at steady state (or within limits).
lol, ok, I did say "(after the transition)"...
you're right, MAF is increasing as RPM increase, so MAF can't be at steady state.
so, for the discussion, does "steady state" mean which of the following:
- airflow is at steady state (or within the limits of steady state);
- cylinder airmass is at steady state (or almost);
- throttle position is at steady state (or within limits).
Steady State is Defined in the tune by a set of Variables....which you can change to suit your needs if you find it necessary or beneficial...
Originally Posted by HP Tuners Help Files
Steady State
A critical part of the dynamic airmass calculation is determination of when the engine is operating at a steady state condition or unsteady (transient) state. During steady state the PCM uses a filtered MAF signal as the basis for airmass calculations, the PCM also calculates a "VE Correction Factor" during steady state. The VE correction factor is simply the ratio of the MAF airmass to the VE airmass and is used to "offset" the VE calculated airmass when a transient is encountered.
During unsteady state, the PCM uses the VE table to calculate airmass and it is offset (multiplied) by the last calculated VE Correction factor. As long as the VE Correction factor is within limits it will accurately offset any differences between MAF and VE table airmasses and the transition between steady and unsteady (transient) prediction will be smooth.
Hi/Lo RPM Threshold: This RPM threshold determines if High or Low steady state determination will be used. If MAP is greater than Hi/Lo MAP Threshold or RPM is greater than Hi/Lo RPM Threshold the High mode settings are used otherwise Low mode settings are used.
Hi/Lo MAP Threshold: This MAP threshold determines if High or Low steady state determination will be used. If MAP is greater than Hi/Lo MAP Threshold or RPM is greater than Hi/Lo RPM Threshold the High mode settings are used otherwise Low mode settings are used.
Lo - MAP Delta: Low mode, MAP change below this will enable steady state.
Hi - MAP Delta: High mode, MAP change below this will enable steady state.
Lo - TPS Delta: Low mode, TPS change above this will disable steady state.
Hi - TPS Delta: High mode, TPS change above this will disable steady state.
Idle - MAP Integ Time: Time that the steady state MAP integrator will run during the idle steady state routine before value is compared to Integrator Threshold to disable steady state.
Idle - MAP Integ Threshold: If steady state MAP Integrator exceeds this threshold during idle steady state then steady state will be disabled.
Idle - VSS Max: Vehicle speed must be below this to enable idle steady state determination.
Idle - TPS% Max: Throttle position must be below this to enable idle steady state determination.
Idle - MAP Int Time En: Time that the steady state MAP integrator will run during the idle steady state routine before value is compared to Integrator Threshold to enable steady state.
Idle - MAP Int Thresh En: If steady state MAP Integrator is below this threshold during idle unsteady state then steady state will be enabled.
A critical part of the dynamic airmass calculation is determination of when the engine is operating at a steady state condition or unsteady (transient) state. During steady state the PCM uses a filtered MAF signal as the basis for airmass calculations, the PCM also calculates a "VE Correction Factor" during steady state. The VE correction factor is simply the ratio of the MAF airmass to the VE airmass and is used to "offset" the VE calculated airmass when a transient is encountered.
During unsteady state, the PCM uses the VE table to calculate airmass and it is offset (multiplied) by the last calculated VE Correction factor. As long as the VE Correction factor is within limits it will accurately offset any differences between MAF and VE table airmasses and the transition between steady and unsteady (transient) prediction will be smooth.
Hi/Lo RPM Threshold: This RPM threshold determines if High or Low steady state determination will be used. If MAP is greater than Hi/Lo MAP Threshold or RPM is greater than Hi/Lo RPM Threshold the High mode settings are used otherwise Low mode settings are used.
Hi/Lo MAP Threshold: This MAP threshold determines if High or Low steady state determination will be used. If MAP is greater than Hi/Lo MAP Threshold or RPM is greater than Hi/Lo RPM Threshold the High mode settings are used otherwise Low mode settings are used.
Lo - MAP Delta: Low mode, MAP change below this will enable steady state.
Hi - MAP Delta: High mode, MAP change below this will enable steady state.
Lo - TPS Delta: Low mode, TPS change above this will disable steady state.
Hi - TPS Delta: High mode, TPS change above this will disable steady state.
Idle - MAP Integ Time: Time that the steady state MAP integrator will run during the idle steady state routine before value is compared to Integrator Threshold to disable steady state.
Idle - MAP Integ Threshold: If steady state MAP Integrator exceeds this threshold during idle steady state then steady state will be disabled.
Idle - VSS Max: Vehicle speed must be below this to enable idle steady state determination.
Idle - TPS% Max: Throttle position must be below this to enable idle steady state determination.
Idle - MAP Int Time En: Time that the steady state MAP integrator will run during the idle steady state routine before value is compared to Integrator Threshold to enable steady state.
Idle - MAP Int Thresh En: If steady state MAP Integrator is below this threshold during idle unsteady state then steady state will be enabled.
Originally Posted by soundengineer
...and no matter what...there is a Variable that commands the MAF to be in 100% control after a certain RPM(typically 4000 rpm in the stock LS1 tune)
11-04-2013, 01:25 AM
#19
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Yes i like to set the VE and/or MAF a little little on the fat side to keep LTFT slightly negative. I find it also helps to slow the LTFT update rate from the stock 0.450 seconds to 1.5 or so. The factory setting results in very fast LTFT updates and is prone to accumulating transient junk, especially when running aggressive DFCO settings.
11-04-2013, 06:57 PM
#20
TECH Senior Member
one thing you are forgetting is that with a MAF... it is commanded to be used according to a variable called "steady state"
. . .