So, how can an LS1 actually run rich?
11-21-2003, 11:21 PM
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So, how can an LS1 actually run rich? I was just thinking about it. So, the stock 02's know on and off, and that's about it. +14.7, and -14.7. Right? So, even if there was, say a ported MAF table in a car with a stock MAF, the 02's would see that there was too much fuel and correct via the LTFT's. Or, by the same token, and intake leak. So, how can a stock or near stock car ever run rich, since the 02's will always correct it, unless it's out of the range they can adjust (like if it read 200% lean).
Along kind of the same lines, we know that large cams dump so much fuel and air through the overlap area that the 02's don't know how to fix it, they see it as running lean since there is unburnt oxygen. But, why do we scale the IFR table to get the LTFT's back in the negative, since all that does is dump more fuel in order to "fool" the oxygen sensors (the mixture in the chamber has now been sacrificed I would think since you are now adding more fuel than needed just so the 02's are okay). It just isn't making any sense to me, but I'm not the brightest buld on the chirstmas tree either
Any thoughts or explainations? I'd like to think I've tuned mine and a couple of my friends cars okay, the WOT stuff is dead on, part throttle all -1 to -2 LTFT's, and so on, but not understanding WHY we're doing what we're doing is bugging me.
Along kind of the same lines, we know that large cams dump so much fuel and air through the overlap area that the 02's don't know how to fix it, they see it as running lean since there is unburnt oxygen. But, why do we scale the IFR table to get the LTFT's back in the negative, since all that does is dump more fuel in order to "fool" the oxygen sensors (the mixture in the chamber has now been sacrificed I would think since you are now adding more fuel than needed just so the 02's are okay). It just isn't making any sense to me, but I'm not the brightest buld on the chirstmas tree either
Any thoughts or explainations? I'd like to think I've tuned mine and a couple of my friends cars okay, the WOT stuff is dead on, part throttle all -1 to -2 LTFT's, and so on, but not understanding WHY we're doing what we're doing is bugging me.
11-22-2003, 07:39 AM
#2
Originally Posted by sbrown99TA
I was just thinking about it. So, the stock 02's know on and off, and that's about it. +14.7, and -14.7. Right? So, even if there was, say a ported MAF table in a car with a stock MAF, the 02's would see that there was too much fuel and correct via the LTFT's. Or, by the same token, and intake leak. So, how can a stock or near stock car ever run rich, since the 02's will always correct it, unless it's out of the range they can adjust (like if it read 200% lean).
Along kind of the same lines, we know that large cams dump so much fuel and air through the overlap area that the 02's don't know how to fix it, they see it as running lean since there is unburnt oxygen. But, why do we scale the IFR table to get the LTFT's back in the negative, since all that does is dump more fuel in order to "fool" the oxygen sensors (the mixture in the chamber has now been sacrificed I would think since you are now adding more fuel than needed just so the 02's are okay). It just isn't making any sense to me, but I'm not the brightest buld on the chirstmas tree either
Any thoughts or explainations? I'd like to think I've tuned mine and a couple of my friends cars okay, the WOT stuff is dead on, part throttle all -1 to -2 LTFT's, and so on, but not understanding WHY we're doing what we're doing is bugging me.
Along kind of the same lines, we know that large cams dump so much fuel and air through the overlap area that the 02's don't know how to fix it, they see it as running lean since there is unburnt oxygen. But, why do we scale the IFR table to get the LTFT's back in the negative, since all that does is dump more fuel in order to "fool" the oxygen sensors (the mixture in the chamber has now been sacrificed I would think since you are now adding more fuel than needed just so the 02's are okay). It just isn't making any sense to me, but I'm not the brightest buld on the chirstmas tree either
Any thoughts or explainations? I'd like to think I've tuned mine and a couple of my friends cars okay, the WOT stuff is dead on, part throttle all -1 to -2 LTFT's, and so on, but not understanding WHY we're doing what we're doing is bugging me.
*You are correct. But, remember WOT/Part Throttle is determined by throttle position %. ->See PE WOT/cold TP%. Part throttle can be either closed or open loop. All PE cells are open loop. We do have part throttle open loop.
*Part Throttle closed loop you are at the mercy of the O2 sensors.
*All PE cells are open loop (PE cells = 3, 7, 11, 12, 13, 14, 15, and 22)- fueling is determined by F/A table (Stoich Table) - Except cell 22-see below, IFR and VE tables and any added fuel, from LTFTs, from the previous closed loop cell. There are other tables which we do not see, yet.....Ken Kelly is still looking for them.
Of course all fueling is dependent on MAF (output) Table as well as Injector Offset Table.
*WOT/PE (PE cell 22)- Fueling ignores F/A table and uses PE/RPM and PE/Temp.
So final AFR WOT/PE = 14.7/(PE/RPM value + PE/Temp value). At normal operating temps the PE/Temp value = 0. Cell 22 is PE/WOT-Unique!! LTFT for WOT/PE should drop to 0 .
*As with other PE cells any added fuel, from LTFTs %, will be added to final PE/WOT fueling (cell 22). So we tune LTFTs to a Negative value and no additional fuel is added. This makes WOT fueling more predictable and stable. Stability is important because you can have a shift of several % in LTFTs ( due to wear and tear in normal engine operation) and as long as the LTFTs are stll negative the WOT/PE AFR will remain the same.
*There is some difference in opinion as to which cells are important in LTFTs. Some say to Average cells 0-15. Others say it's only important to make sure all PE cells (3, 7, 11, 12, 13, 14, 15, 22) are negative.
I used the averaging method, but at this point I think the PE cells method makes better sense since these are the High RPM and High Load cells. FWIW.
* Hope this helps some. Actually helped me going through it. If anyone sees a mistake please chime in.
joel
Last edited by binksz06; 11-22-2003 at 07:54 AM.
