Exactly. Making the map/histogram is a PIA. On a side note some trucks i have messed with responded well to tweaking the switchpoints however some made no change at all. Weird yes.

 

That's why I wanted a clarification. My truck doesn't seem to care where the switchpoints are...it kinda does it's own thing, lol.

 

So adjusting your switchpoints did not change your ltfts at all? Did you map your closed loop modemto the appropriate air mass to then use your average ltft to apply the correction or did you just move them at random?

Also how much did you change the values, from my experience it takes a change from 450mv to 350mv to even begin altering the ltft

 

I randomly moved them a while back, just to see what, if any, effect on fuel trims it would make. I am 99% sure that I moved them at least 100mV, probably more.

Thinking back, this was back before my longtube swap (which also meant I swapped to new O2's), which was in November 2009...so it's been awhile and I haven't tried it again since.

 

Ok cool i was just wondering. Like i mentioned before on some trucks it works others it does not do a damn thing

On a side note i wonder if "closed loop mode" is a valid loggable PID

 

I dont use LTFTs, no need if your tune is close. STFTs can compensate up to 50%.

I trust the narrowband o2s more than the wideband. If they dont agree at stoich then I see that as a problem with the wideband calibration, not with the o2s.

 

Don't the LTFT's learn off the STFT's?
I hear of alot of guys just leaving them turned off (LTFT's) but I haven't paid attention to whether thats for SD or MAF.

 

If your tuning is dead nuts, you don't need any trims. I have tuned some OLSD setups that wouldn't have it any other way, I like to have a pad there incase something happens.

 

God forbid any of the senior tuners over on the HPTuners boards see you say this, lol.

And something I thought of after my previous post, MAF tuning helps to dial in the LTFT's as well, should a person choose to use MAF and LTFT's.

 

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!