Ground offsets
12-30-2007, 10:17 PM
#1
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Ground offsets
I have read about ground offsets in reference to wideband O2's but never really understood them. I am not an electrician but have a basic understanding. What is happening that causes a ground offset and how can it be corrected? Are there other aftermarket parts that can be affected by a ground offset (boost controller, alky injection)?
12-30-2007, 10:30 PM
#2
I believe it's the heater circuit in the sensor that causes havoc. It is unreliable, under wired (needs larger gauge wire) and there are a ton of "wiring" ways to get you close. First thing is first, I say get a battery ground into your cab so you can ground everything involved with your WB to it. Fair game. Second, is a calc fix.
http://www.hptuners.com/forum/showthread.php?t=5267
http://www.hptuners.com/forum/showthread.php?t=5267
12-30-2007, 11:03 PM
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OK, I'll pull a battery ground inside. I have an LC-1 with an XD-16 gauge, my gauge seems to read .2-.3 AFR higher than my scantool (EFI live) at stoich. Is this showing me my offset? I read the HPT thread but need to go through it again. Thanks dew!
01-02-2008, 11:52 AM
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Do you have V1 or V2?
A few short words about the LC-1.... 0-5 volt sensor, fairly precise for the money. The raw output of the sensors' digital signal is processed and fed directly into the controller and output'd directly to LogWorks via your serial to USB conveter. The analog signal you use for your datalogger is processed by a Digital to Analog Converter chip (DAC) to channel 1- yellow wire and channel 2 brown wire.
There are two flavors of the LC-1 6 wire and 7 wire. The extra wire is for a analog ground. If you have the 7 wire version put that ground to your data logger analog input ground. The blue wire, heater ground should be tied to the system ground, white wire. If you have a 6 wire LC-1 then, jumper another wire off this pair and send it to the data logger ground.
The offset is a representation of the difference in potential btw the digital output and the analog output. This is very rarely, if ever going to be small enough not to make a difference in what is displayed btw what you will see in LogWorks and your datalogger. LogWorks, the digital signal, best represents the actual sensor is reading in the exhaust.
You will have to make up the difference in your data logger's calculated pid.
If you have an EFI Live V2 there is a provision in the scantool (Little V2 icon) for taking this offset in to account.
Think of the LC-1 as a programable power supply and your data logger as a voltmeter. Program your LC-1 to put out a flat 1vdc signal from 10 to 20 AFR on channel 1. With the scantool connected to the vehicle press the V2 icon. Have the LC-1 channel 1 yellow wire plugged into the "+" side of the V2 analog channel 1. Plug in the aforementioned ground to the "-" of the V2's channel 1. Uncheck all of the other 4 channels in the scantool. With a solid ready light on your LC-1 (or verify system is running with logworks if you don't have the cal/indicator LED rigged up) press the "Initialize" button in the scantool. Close LogWorks if opened. Open LM Programer, (As soon as you open LMPrgrmr your LED will blink indicating it is in prgm mode) Program channel 1 for a 4 volt flat line from 10 to 20 AFR. Close the LM Programer software, unplug the USB to serial adapter and the little orange analog input connector to the V2 and cut off system power to the LC-1- Note the LC-1 system indicator LED should extinguish- If not, something is not unplugged. Keep the vehicle key on, with the scantool connected the whole time. Re boot the LC-1 by applying system power first then, connect the USB to serial adapter and the analog out to the V2. Wait for the LC-1 ready light. Now hit the "Calibrate" button in the scantool. If you hit the "test" button you should be "seeing" / "reading" what the volt meter inside the V2 really is and the offset. Hit stop, pull up LM Programer and re-configure channel 1 for
.883 -> 10 AFR and 4.215 -> 20AFR. Power down the LC-1, and reboot as described before.
Now, with your LC-1 re-booted close the scantool calibate page and pull up LogWorks. Start the vehicle and start logging with the scantool, the two should the same now.
Other notes, make sure you have good battery before you attempt to perform this operation. Any wierd, bizzare stuff is a result of not fully powering down or booting up the LC-1 correctly or crappy battery.
The V1 does not have this feature availible in the scantool so you will have to modify the PID- you can use the same logical procedure, you will just have to do it yourself with the information from the data page of the scantool.
A few short words about the LC-1.... 0-5 volt sensor, fairly precise for the money. The raw output of the sensors' digital signal is processed and fed directly into the controller and output'd directly to LogWorks via your serial to USB conveter. The analog signal you use for your datalogger is processed by a Digital to Analog Converter chip (DAC) to channel 1- yellow wire and channel 2 brown wire.
There are two flavors of the LC-1 6 wire and 7 wire. The extra wire is for a analog ground. If you have the 7 wire version put that ground to your data logger analog input ground. The blue wire, heater ground should be tied to the system ground, white wire. If you have a 6 wire LC-1 then, jumper another wire off this pair and send it to the data logger ground.
The offset is a representation of the difference in potential btw the digital output and the analog output. This is very rarely, if ever going to be small enough not to make a difference in what is displayed btw what you will see in LogWorks and your datalogger. LogWorks, the digital signal, best represents the actual sensor is reading in the exhaust.
You will have to make up the difference in your data logger's calculated pid.
If you have an EFI Live V2 there is a provision in the scantool (Little V2 icon) for taking this offset in to account.
Think of the LC-1 as a programable power supply and your data logger as a voltmeter. Program your LC-1 to put out a flat 1vdc signal from 10 to 20 AFR on channel 1. With the scantool connected to the vehicle press the V2 icon. Have the LC-1 channel 1 yellow wire plugged into the "+" side of the V2 analog channel 1. Plug in the aforementioned ground to the "-" of the V2's channel 1. Uncheck all of the other 4 channels in the scantool. With a solid ready light on your LC-1 (or verify system is running with logworks if you don't have the cal/indicator LED rigged up) press the "Initialize" button in the scantool. Close LogWorks if opened. Open LM Programer, (As soon as you open LMPrgrmr your LED will blink indicating it is in prgm mode) Program channel 1 for a 4 volt flat line from 10 to 20 AFR. Close the LM Programer software, unplug the USB to serial adapter and the little orange analog input connector to the V2 and cut off system power to the LC-1- Note the LC-1 system indicator LED should extinguish- If not, something is not unplugged. Keep the vehicle key on, with the scantool connected the whole time. Re boot the LC-1 by applying system power first then, connect the USB to serial adapter and the analog out to the V2. Wait for the LC-1 ready light. Now hit the "Calibrate" button in the scantool. If you hit the "test" button you should be "seeing" / "reading" what the volt meter inside the V2 really is and the offset. Hit stop, pull up LM Programer and re-configure channel 1 for
.883 -> 10 AFR and 4.215 -> 20AFR. Power down the LC-1, and reboot as described before.
Now, with your LC-1 re-booted close the scantool calibate page and pull up LogWorks. Start the vehicle and start logging with the scantool, the two should the same now.
Other notes, make sure you have good battery before you attempt to perform this operation. Any wierd, bizzare stuff is a result of not fully powering down or booting up the LC-1 correctly or crappy battery.
The V1 does not have this feature availible in the scantool so you will have to modify the PID- you can use the same logical procedure, you will just have to do it yourself with the information from the data page of the scantool.
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