LTFT's "Disabled"...good, bad, or otherwise???
02-12-2011, 02:29 PM
#21
One last thing that I don't think many tuners even know about or mess with is the Transport Delay or "flight time". The Transport Delay is the time from when the injector begins spraying fuel to when the O2 sensor applies a correction to the fueling. Now when we install longtube headers and we move the O2 sensors farther away from the factory stock location this adds about 25%-30% to the Transport Delay times. Correcting this by adding this 25% or so to the Transport Delay can help to bring things back in line.
Now that I am done with my rambling on and on I run with LTFTs disabled for the most part, the STFTs do the job of making the fueling corrections.
Everybody have a good day!
Now that I am done with my rambling on and on I run with LTFTs disabled for the most part, the STFTs do the job of making the fueling corrections.
Everybody have a good day!
I was also curious what you mean by LTFT's disabled "for the most part"? Are you saying you use them just partially? Or did I miss something?
02-12-2011, 02:45 PM
#22
Good points brought up, klug. I found my stoich to be around 14.4 with the 10% ehh they have around here. Easy way to test is put the truck in closed loop and log trim and wideband and drive in constant conditions on the highway and compare wideband error to stft's. They should be the same, or at least very close in stoich cells. If they differ by more than a few percent your stoich value in the tune needs to be adjusted.
02-12-2011, 02:49 PM
#23
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The reason why that is preached so much is because the narrowbands do have a "deadband" of about 3%. What do I mean by "deadband" you ask? Well the reason for that term is because of the fact that the narrowbands do not switch until they are actually past the target which is stoich (lambda 1) thus the reason the switchpoints voltages are labeled Rich/Lean. You guys with hpt or efi live go out and take a log in closed loop and you clearly see in the chart view of the scanning where the O2s are switching just rich of stoich and then just lean of stoich, back and forth back and forth.
Now in open loop using a wideband you are no longer trying to hit a moving target. Ok I know what everybody is thinking and have seen it first hand no matter what happened tuning in open loop with the wideband when in closed loop the narrowbands take over and are doing their job which is keeping the fueling centered around stoich in which they do a very good job of that and are very accurate in doing so. The OEM has spent tons of time making sure of this especially these days with the emisions standards getting tighter and tighter. Now with that said I trust the narrowband O2s very much as long as they don't have a million miles on them and aren't 10 years old they are still very accurate. When you get some older ones with some miles on them they may not be switching like they should tuning evrything with the wideband is sounding even better to make certain that your commanded afr and actual afr are dead nuts on.
I was reading thru this thread and also had seen where it was brought up about the wideband and narrowbands not matching up and agreeing with each other. Yes definately a problem I have seen and have read many many many threads on the forums about. The first very important thing to make sure of is that the stoich afr table in the tune is set to match our wonderful ethanol blended fuels that is in our tanks these days. Because if this is set to 14.68, etc... which is the stoichiometric value for straight gas but their is E10 in the tank which is close to what you will find most places in the country these days which has a stoich value of around 14.1-14.2 that doesn't quite pan out. So if we have tuned all part throttle areas with our wideband to 14.7 which is what almost every wideband's stoich is defined as and then we go back to closed loop and now the narrowbands are going to be keeping the fueling centered around stoich for whatever fuel is in the tank. Obviously fuel trims could or will be off. I have proved this many times with some testing.
Like Atomic basically stated do we trust our wideband? With a decent wideband and a sensor that's not old and worn out I like to always think I can trust my wideband and I do and we also need to make sure we don't have any offsets between what the wideband is reporting and what we are seeing in the scanner which is important for things to match up.
One last thing that I don't think many tuners even know about or mess with is the Transport Delay or "flight time". The Transport Delay is the time from when the injector begins spraying fuel to when the O2 sensor applies a correction to the fueling. Now when we install longtube headers and we move the O2 sensors farther away from the factory stock location this adds about 25%-30% to the Transport Delay times. Correcting this by adding this 25% or so to the Transport Delay can help to bring things back in line.
Now that I am done with my rambling on and on I run with LTFTs disabled for the most part, the STFTs do the job of making the fueling corrections.
Everybody have a good day!
Now in open loop using a wideband you are no longer trying to hit a moving target. Ok I know what everybody is thinking and have seen it first hand no matter what happened tuning in open loop with the wideband when in closed loop the narrowbands take over and are doing their job which is keeping the fueling centered around stoich in which they do a very good job of that and are very accurate in doing so. The OEM has spent tons of time making sure of this especially these days with the emisions standards getting tighter and tighter. Now with that said I trust the narrowband O2s very much as long as they don't have a million miles on them and aren't 10 years old they are still very accurate. When you get some older ones with some miles on them they may not be switching like they should tuning evrything with the wideband is sounding even better to make certain that your commanded afr and actual afr are dead nuts on.
I was reading thru this thread and also had seen where it was brought up about the wideband and narrowbands not matching up and agreeing with each other. Yes definately a problem I have seen and have read many many many threads on the forums about. The first very important thing to make sure of is that the stoich afr table in the tune is set to match our wonderful ethanol blended fuels that is in our tanks these days. Because if this is set to 14.68, etc... which is the stoichiometric value for straight gas but their is E10 in the tank which is close to what you will find most places in the country these days which has a stoich value of around 14.1-14.2 that doesn't quite pan out. So if we have tuned all part throttle areas with our wideband to 14.7 which is what almost every wideband's stoich is defined as and then we go back to closed loop and now the narrowbands are going to be keeping the fueling centered around stoich for whatever fuel is in the tank. Obviously fuel trims could or will be off. I have proved this many times with some testing.
Like Atomic basically stated do we trust our wideband? With a decent wideband and a sensor that's not old and worn out I like to always think I can trust my wideband and I do and we also need to make sure we don't have any offsets between what the wideband is reporting and what we are seeing in the scanner which is important for things to match up.
One last thing that I don't think many tuners even know about or mess with is the Transport Delay or "flight time". The Transport Delay is the time from when the injector begins spraying fuel to when the O2 sensor applies a correction to the fueling. Now when we install longtube headers and we move the O2 sensors farther away from the factory stock location this adds about 25%-30% to the Transport Delay times. Correcting this by adding this 25% or so to the Transport Delay can help to bring things back in line.
Now that I am done with my rambling on and on I run with LTFTs disabled for the most part, the STFTs do the job of making the fueling corrections.
Everybody have a good day!
Im tuning a car that jus had full exhaust done long tubes and all.Im gonna give the transport delay idea a shot.This is somthin found in Hpt,and efilive correct?
02-12-2011, 08:21 PM
#24
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Oops sorry I forgot to mention in Ford calibrations it's labeled Transport Delay, in the GM cal go to Fuel>Open & Closed Loop>Closed Loop Integrator Delay>Airflow Mode
Yeah I always run with just STFTs and LTFTs disabled, "for the most part" is just part of the goofy way I word stuff sometimes.
02-12-2011, 08:28 PM
#25
Oops sorry I forgot to mention in Ford calibrations it's labeled Transport Delay, in the GM cal go to Fuel>Open & Closed Loop>Closed Loop Integrator Delay>Airflow Mode
Yeah I always run with just STFTs and LTFTs disabled, "for the most part" is just part of the goofy way I word stuff sometimes.
Yeah I always run with just STFTs and LTFTs disabled, "for the most part" is just part of the goofy way I word stuff sometimes.
Gotcha. Thanks again for sharing.
02-12-2011, 09:30 PM
#28
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Also to add to what Corey had mentioned earlier in the thread about lowering the switchpoints is effective but it is hit or miss depending on the operating system from what I have seen.
Lowering the switchpoints can effectively lean it out some in closed loop and perhaps help mileage out some. In an 05 GTO I had done for a guy he was looking for better mileage along with more performance because he drove the car daily for work and he swears up and down that he gained 3 mpg and I had lowered the O2 switchpoints in that tune.
But a decent amount of that may have also been attributed to the fact that he had made some moderate changes to the car and it just needed to be tuned badly anyways.
Lowering the switchpoints can effectively lean it out some in closed loop and perhaps help mileage out some. In an 05 GTO I had done for a guy he was looking for better mileage along with more performance because he drove the car daily for work and he swears up and down that he gained 3 mpg and I had lowered the O2 switchpoints in that tune.
But a decent amount of that may have also been attributed to the fact that he had made some moderate changes to the car and it just needed to be tuned badly anyways.
02-12-2011, 09:38 PM
#29
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Now I will say I have seen some better oscilation and switching out of the O2s but just a note to everybody this isn't a ground breaking proof positive fix for the guys having some problems with their O2s switching after the installation of longtubes. But as I stated the values that are in a stock tune are based on the narrowbands being in the stock factory location which obviously after a change to longtubes they are no longer in that position.
