PLX, V2 Voltage Offset - HELP!

[JezzaB]

Hey guys,
Im tearing my hair out. I have posted that awhile ago my V2 suddenly went out of calibration. I recalibrated it and thought that it was ok but its not. Ive tried outputing the voltages with

-Batteries
-Variable power supply
-The PLX (2.34 unplugged and 5v plugged in free air)

They all work bang on for the 2 reference voltages but it reads around 100mv out everywhere else. It reads lean and it just makes it richer and richer when doing an autove. Embarrasing when you tune a car and its using more fuel.

I tuned a car before the calibration dramas and its LTFT's were great.

One example is I held a load point and constant voltage (within 50mv) 1650mv in efilive and when I pull it off the V2 and put the multimeter on it, it reads around 1520mv, then put the V2 back on and its 1650mv.

I just dont know what else to do.

Jez

[joecar]

Does post #2 of this thread help: showthread.php?t=4593

[dc_justin]

Does post #2 of this thread help: showthread.php?t=4593

PLX's aren't programmable like that, unfortunately.

I'm experiencing the same voltage offset with mine, but it tends to drift around a bit. One time, 5v will be 5.15v in FS. The next, 5.36v. Had it hooked up to an autronic a few weeks back and it read dead on. WB power was hooked directly to the battery, so that might be part of the difference, but it otherwise appears that the WB is the culprit...

[JezzaB]

Does post #2 of this thread help: showthread.php?t=4593

Yup. Ive followed that guide to the letter for every calibration using different power sources.

As said above, the PLX can only really output 2 voltages

2.34v if the WBO2 is unplugged from the controller and
5.00v free air reading

Got me stumped.

Jez

[SinisterSS]

Double check your earth/ground connection. For best results I have the EFILive box ground point wired to the same point on the chassis as the PLX WBO2.

[Doc]

I agree, ground offsets can be a bitch.

[Blacky]

The guys that designed FlashScan have been hard at work figuring out what can be done to limit external influences on the WB voltage as read by FlashScan.

The best solution is to use the RS232 serial link into FlashScan and get an exact digital wide band AFR value. The serial interface is being developed for the next major FlashScan firmware update. The LC1 will be the first wide band supported by FlashScan's RS232 interface.

The next best option is to return your FlashScan unit to EFILive. We can replace some of the components in FlashScan to higher specification parts. Parts with smaller errors and better resilliance against ground offset issues. These parts cost more but testing has shown that with the higher quality parts we can reduce ground voltage influences that can otherwise cause up to 50mV variance.
This upgrade is not free, but EFILive has decided to subsidise the upgrade and the final cost should be less than $20 (plus shipping).
I highly recommend getting this upgrade done. We will announce a formal upgrade procedure very soon on our web site.

Another option is to make sure all ground points are as resistance free as possible. Running a low resistance ground wire from the wide band directly to the battery negative terminal helps.

Lastly, some grounds change then the ignitions is switched on. What appears to be a goo dground with the igntion off can have a small voltage when the ignition is turned on and even more so when the engine is running and the alternator is charging. So when you are checking for ground issues, check under all three cases: Ignition off, Ignition on and Engine on.

Regards
Paul

[JezzaB]

The guys that designed FlashScan have been hard at work figuring out what can be done to limit external influences on the WB voltage as read by FlashScan.

The best solution is to use the RS232 serial link into FlashScan and get an exact digital wide band AFR value. The serial interface is being developed for the next major FlashScan firmware update. The LC1 will be the first wide band supported by FlashScan's RS232 interface.

The next best option is to return your FlashScan unit to EFILive. We can replace some of the components in FlashScan to higher specification parts. Parts with smaller errors and better resilliance against ground offset issues. These parts cost more but testing has shown that with the higher quality parts we can reduce ground voltage influences that can otherwise cause up to 50mV variance.
This upgrade is not free, but EFILive has decided to subsidise the upgrade and the final cost should be less than $20 (plus shipping).
I highly recommend getting this upgrade done. We will announce a formal upgrade procedure very soon on our web site.

Another option is to make sure all ground points are as resistance free as possible. Running a low resistance ground wire from the wide band directly to the battery negative terminal helps.

Lastly, some grounds change then the ignitions is switched on. What appears to be a goo dground with the igntion off can have a small voltage when the ignition is turned on and even more so when the engine is running and the alternator is charging. So when you are checking for ground issues, check under all three cases: Ignition off, Ignition on and Engine on.

Regards
Paul

This is great information and I will be looking into this upgrade when its available.

Jez

[69camaro5speed]

sounds like my lm1.my own car i used a lc1 worked great.when in closed lop would read 14.6 to 14.7 and the comanded allways stayed very close to the lc1. on my lc1 i used the extra ground the the chassis. i thought about running one on my lm1 but it didnt say to with it.i could have my lm1 reading dead on 14.7 open loop doing the auto tune just enable closed loop and it would change.open loop again back to 14.7 same day just mins apart tryed it on 4 differant auto tune cars all did the same with my lm1.the lc1 with extra ground didnt do it.so guessing running a extra ground from the lm1 to car chassis should be ok to try ? dont remember reading it needed to be done.but did wounder my not

[Bruce Melton]

Seems that V1 is accurate and V2 less so?
If I logged same car with both units the V2 seems skewed. Did a exhaustive calibration using power supply which helped, but V2 still seems to be variable compared to PLX display.