Help tuning a 427 with an E38 PCM, lean condition, O2s going wild
01-15-2008, 10:48 PM
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Help tuning a 427 with an E38 PCM, lean condition, O2s going wild Just installed an L92 based 427 in a 2006 corvette, a6. Can't get the part throttle/idle AFRs correct. After the car goes into open loop, the PCM pulls more than 20% fuel and goes WAY lean. Only way I've found to correct is to go into open loop again. low freq MAF table does nothing, no VE table in the E38. When this condition occurs, the O2 voltage values "cycle" from around 50 mv to 900 mv, then repeat forever. Files can be found here: http://www.hptuners.com/forum/showthread.php?t=16094
Any help or suggestions would be greatly appreciated... I just want to drive this thing again...
Any help or suggestions would be greatly appreciated... I just want to drive this thing again...
01-15-2008, 11:44 PM
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Tried it a couple of ways for the base file, but due to it being an E38 we don't have many choices, especially with an A6. The injectors are LS3/7, so I used the IFR values from a Z06. When in open loop, it's very easy to control the fuel and even with the stock LS2 values, it wasn't that far off. It's just closed loop that we can't get any control over.
01-17-2008, 09:23 AM
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Tried again with some more tweaking last night, it seems to be directly caused by the O2s switching from rich to lean, back and forth, all the time at idle and off-idle engine speeds. The computer just starts pulling fuel as indicated by the fuel trims. Seems like the Cam overlap/new distance the O2 is from the header is causing the computer some trouble.
Is there a way in the E38 to buffer the O2 readings as the distance is now different? I've read about O2 integrator delay, but can't find it in the E38.
Is there a way in the E38 to buffer the O2 readings as the distance is now different? I've read about O2 integrator delay, but can't find it in the E38.
01-17-2008, 05:26 PM
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Just installed an L92 based 427 in a 2006 corvette, a6. Can't get the part throttle/idle AFRs correct. After the car goes into open loop, the PCM pulls more than 20% fuel and goes WAY lean. Only way I've found to correct is to go into open loop again. low freq MAF table does nothing, no VE table in the E38. When this condition occurs, the O2 voltage values "cycle" from around 50 mv to 900 mv, then repeat forever. Files can be found here: http://www.hptuners.com/forum/showthread.php?t=16094
Any help or suggestions would be greatly appreciated... I just want to drive this thing again...
Any help or suggestions would be greatly appreciated... I just want to drive this thing again...
Easy way to fix this is to ditch the MAF sensor , tune the VE table in EFILIVE ( I believe HPT also have a custom OS you can purchase that will allow this ) and then the PCM wont need to pull or add fuel as the fuel equation once tuned will be spot on.
Very hard to get the maf scaling right on a big cammed cubed engine any other way.
