I'm trying to setup my Datalogit to reference my PLX (AFR, FEGT, REGT, FP) gauges, but I'm having some calibration issues. All of the inputs are linear, but when I put in the voltage and scale information the readings the Datalogit are getting are way off compared to what my actual gauges are reading.

Here is all the scaling information

http://www.plxdevices.com/Installati...UsersGuide.pdf

http://www.plxdevices.com/Installati...UsersGuide.pdf

http://www.plxdevices.com/Installati...UsersGuide.pdf

Do you think I have a bad ground or something else?

 

Well, how do you have your grounds and other wires run? Can you put a diagram together?

 

I'm having this same problem. I figured I'd bump this thread instead of starting another one.

I have 2 SM-EGTs and an SM-AFR hooked up to a DM-100 gauge.

I'm trying to get the sensors to interface with my (black box) datalogit.

Currently I am running the lower right "analog out" pin on the AFRs to the aux inputs on the datalogit.

I have the datalogit parameters set up such that 0V=0 degrees C and 5V= 1502 degrees C, as per what I've inferred from these instructions;

http://www.plxdevices.com/Installati...UsersGuide.pdf

The values on the PLX gauge seem about right, but the values in the datalogit are way off. This leads me to believe it's a wiring or calibration issue.

The car is not currently running as I am waiting on a tune so, I don't have a lot of ability to test different values.

Any suggestions?

 

It is essential that the PLX provided capacitor is installed across AN1 and AN2 along with the SM-AFR wiring (I put the WB out on AN1 and GND on AN2) and the Datalogit and PLX grounds reference to the same location if not the same connect point like I have it in the pic.
No doubt you are using the 0-5V linear wideband output - right?

 

Grounded on the same point, and yes, I'm using the 0-5V "wideband" pin. I'll be putting the cap in tomorrow. I haven't paid that much attention to the wideband yet, since I can't run the vehicle yet so I don't have any solid data to compare the accuracy.

Will I need to use the ground pins on the AFRs as well?

Thanks for the help!

 

When I grounded my wideband to that nut/bolt in the photo, it caused issues with my car due to the common ground with the ECU

 

All grounds need to be used.

FYI for my 94 the PLX NB out provides the O2 data to the PFC so I can run the engine in FB mode. It works just fine and I don't have two sensors.
You need common ground planes without appreciable resistance measurement between them especially between devices that share signals. Ground loop noise and feedback is a problem with these cars.
$lacker - very suprised you have this issue; can't really understand it...

Another little know issue with the PLX is their oscillators in the sensor boxes are very "dirty" and transmit noise through the power and data cabling. If you happen to run one of the cables around your sound system head unit you will hear it..... PLX confirmed this is an issue; don't know it they did anything about in follow-on products. Just an FYI.

 

I made a thread on the issue before figuring out the source of it
Long story short: there's already a ground on that point from the car's harness (at least there is on my RHD car). When I grounded my WB02 there it caused the RPM gauge to bounce when the car was off (in addition to other related issues
Moved the ground to somewhere else and everything has been fine since

 

So, just to clarify;

all three sensors will have 2 wires coming from them (signal and ground), going to two coupled Dataloggit inputs?