Technical TA crazy fuel trim values from OBD/Torque

[Dingo]

Hi all

I use the Torque app to watch various engine values after my oil mishap a couple of months ago. Performance is fine and I haven't had any OBD error codes. I've noticed though that the short and long term fuel trim values as logged by Torque are mad - I've attached a typical log graph.

I know the values can't be right because the long term fuel trim is bouncing around and I'd be getting the check engine light if the values were real!

Has anyone else noticed this? Is Torque picking up the wrong PIDs or assuming the wrong units?

Ian

 

[AGH1965]

I remember forum member UFI noticed something similar. See: https://www.fiatforum.com/500/418458-twinair-remap-8.html?p=4022947

 

[zanes]

Does look like they track RPM quite well though.

 

[Dingo]

I remember forum member UFI noticed something similar. See: https://www.fiatforum.com/500/418458-twinair-remap-8.html?p=4022947

Well they definitely match UFI's description of "random"!

I thought I had set it to log the O2 sensor values as well but they didn't appear in the log so I'll have to try again for those.

Presumably these trim values are just gobbledook?

 

[UFI]

I've found you can't really trust standard OBD tools to work with a TA. The Load (calculated from the MAF) should range from 0-100%,the TA tends to stay in the 0-30 region, but sometimes shoots up to 80% for no apparent reason. Fuel trim is another, and I can't remember my conclusion on the 02 sensors.

It's not entirely unusual, many cars will show some discrepancies vs factory diagnostic equipment.

 

[AGH1965]

When I looked with a generic OBD tool at the ignition timing of a TA that was running idle, the values didn't seem plausible either. They were constantly jumping up and down by more than 60 (!!!) degrees, although the engine was running smoothly. Apparently FIAT offers several "funny" signals on the OBD connector. Maybe to annoy the competition. Who knows?

 

[UFI]

Yes, I've found that too. On the other hand it's the only car I've got that reports fuel level via OBD, and apparently correctly. Quite useful when you usually run it down to one litre or less.

Down the track I will probably wire in a dedicated system where each sensor is wired in and calibrated by the user. Of course, some values are only reported by the ECU and can't be read this way.

 

[Dingo]

I've been out again and successfully logged the O2 sensor values (see attached graph, hope it's readable!) Unlike the fuel trim values these appear to be genuine...