Determining BSFC map from logged OBD2 data

[monroe74]

Originally Posted by fumesucker

I think I may have found the software that will calculate a BSFC map from the OBD2 data..

That's an interesting product. Thanks for pointing it out.

I see that they are displaying and logging lots of OBD2 data. But I don't see where they are attempting to do any power calculations, like BSFC. So I guess you could export the raw data and apply your own procedure for deriving BSFC, but I think most of that work is going to happen outside this program. They're giving you raw speed data, but you have to translate that into acceleration, and then translate that into power, and then relate that to fuel use.

The power calculation includes tricky factors like whether or not you're traversing a grade, and the effect of aero drag at different speeds. These calculations are much simpler if you live on a planet with no hills and no atmosphere. Anyway, I don't see where that program attempts to tackle these issues. But maybe it's in there and I didn't notice!

And there's a separate issue, which I think you already know about. OBD (at least for most makers) doesn't read the injectors. So any fuel-use calculation is some kind of calculated approximation, based on things like air flow. This is how the Scangauge works, and I think under certain conditions it creates problems with accuracy.

Either way, I'm interested in hearing more about what you're doing, because I think you're on the right track and you're inevitably going to make helpful discoveries.