LTFT are lean, wideband is rich, now what??
07-03-2005, 06:58 PM
#1
TECH Resident
Thread Starter
LTFT are lean, wideband is rich, now what?? I'm seeing LTFT's of 2 to 4 or higher most of the time I'm cruising, and WOT 5 or 10. This looks a little bit lean, the PCM is adding fuel, the numbers are never negative.
New O2 sensors last week. This is with the new 30lb SVO injectors and the IFR at 138% and the PE at 93%. But my wideband ( just calibrated )
tells me that I am running 14.2 at cruise and 11.75 WOT --Rich?
So where do I go from here? Is the PCM thinking it's lean and over compensating with too much fuel. The wideband doesn't lie, does it ?? It looks like if I lean out the IFR and PE, the LTFT's will just add more fuel. What should I try next?
Thanks
New O2 sensors last week. This is with the new 30lb SVO injectors and the IFR at 138% and the PE at 93%. But my wideband ( just calibrated )
tells me that I am running 14.2 at cruise and 11.75 WOT --Rich?
So where do I go from here? Is the PCM thinking it's lean and over compensating with too much fuel. The wideband doesn't lie, does it ?? It looks like if I lean out the IFR and PE, the LTFT's will just add more fuel. What should I try next?
Thanks
07-03-2005, 07:10 PM
#2
On The Tree
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It doesn't sound like either one is lying.
14.2 @ cruise is considered pretty much normal. It should be 14.7 but its in the proximity and the computer may lean it out a little for cruise to increase fuel economy. Also remember that the fuel trims are compensating so that the A/F mixture is close to 14.7:1. So regardless of -10% fuel trim or positive 10% fuel trim, it should be 14.7 or close inside the combustion chamber. Fuel trim is just telling you what the computer had to do to get the mixture to 14.7.
At WOT, the computer goes into Power Enrichment (or PE). When this occurs, the PCM adds much more fuel and as a result, disables fuel trims, so you can't go by fuel trims at WOT, thats why you rely on the Wide Band.
I hope this made sense.
14.2 @ cruise is considered pretty much normal. It should be 14.7 but its in the proximity and the computer may lean it out a little for cruise to increase fuel economy. Also remember that the fuel trims are compensating so that the A/F mixture is close to 14.7:1. So regardless of -10% fuel trim or positive 10% fuel trim, it should be 14.7 or close inside the combustion chamber. Fuel trim is just telling you what the computer had to do to get the mixture to 14.7.
At WOT, the computer goes into Power Enrichment (or PE). When this occurs, the PCM adds much more fuel and as a result, disables fuel trims, so you can't go by fuel trims at WOT, thats why you rely on the Wide Band.
I hope this made sense.
07-03-2005, 11:21 PM
#3
If you are trying to adjust your fueling with the IFR table, then you are going about it all wrong. You need to set the IFR table to where it needs to be and leave it alone. Then adjust the fueling with the VE table. I just tuned a H/C car today with SVO 30'lbers and only touched the IFR table at the begining to get it inline. All the fueling needs to be adjusted first with the VE, MAF unplugged. Then after the VE is dialed in, re-enable the MAF and calibrate it. Then adjust PE for WOT. I would tune the car in open loop first, then if you want, re-enable closed loop. If you are using EFI Live you can do it all with the software and not need any spreadsheets. Also make sure you have turned COTS off. That may cause a rich condition at WOT.
07-03-2005, 11:41 PM
#4
Originally Posted by SUPRYZE
It doesn't sound like either one is lying.
14.2 @ cruise is considered pretty much normal. It should be 14.7 but its in the proximity and the computer may lean it out a little for cruise to increase fuel economy. Also remember that the fuel trims are compensating so that the A/F mixture is close to 14.7:1. So regardless of -10% fuel trim or positive 10% fuel trim, it should be 14.7 or close inside the combustion chamber. Fuel trim is just telling you what the computer had to do to get the mixture to 14.7.
At WOT, the computer goes into Power Enrichment (or PE). When this occurs, the PCM adds much more fuel and as a result, disables fuel trims, so you can't go by fuel trims at WOT, thats why you rely on the Wide Band.
I hope this made sense.
14.2 @ cruise is considered pretty much normal. It should be 14.7 but its in the proximity and the computer may lean it out a little for cruise to increase fuel economy. Also remember that the fuel trims are compensating so that the A/F mixture is close to 14.7:1. So regardless of -10% fuel trim or positive 10% fuel trim, it should be 14.7 or close inside the combustion chamber. Fuel trim is just telling you what the computer had to do to get the mixture to 14.7.
At WOT, the computer goes into Power Enrichment (or PE). When this occurs, the PCM adds much more fuel and as a result, disables fuel trims, so you can't go by fuel trims at WOT, thats why you rely on the Wide Band.
I hope this made sense.
07-04-2005, 12:01 PM
#6
TECH Resident
Thread Starter
My LTFTs have been all positive, so when I hit WOT it is adding a positive number. It looks like it is adding something close to the average LTFT.
Question; to rescale the VE table, If I unhook MAF and run for an hour, then scan, what data am I looking for to use in the rebuild of the VE table. I have LS1edit, will it work, maybe it's time to upgrade.
What is the best programming tool? HPtuner??
Question; to rescale the VE table, If I unhook MAF and run for an hour, then scan, what data am I looking for to use in the rebuild of the VE table. I have LS1edit, will it work, maybe it's time to upgrade.
What is the best programming tool? HPtuner??
