I recently got a Kiwi Wifi and Dashcommand for my 2011 Hyundai Elantra Touring automatic transmission (http://www.hyundaiusa.com/elantra-touring/specifications.aspx
I put in a new vehicle and set the engine displacement to 2L. Everything connects and starts displaying data.
However, the fuel consumption data is wildly innacurate, like 30-50% too high. For example, I've tracked fuel consumption manually for the last 5000km, and the average is 8.7L/100KM. Dashcommand's average currently shows 15.9 (i've reset it recently, but on a 200km trip recently it was 14.3 L/100km instead of 8.4 that I calculated from a fillup before/after.
I suppose I could do the fillup correction, but the manual states that it is optional, and everything I've read about systems like this is that they should be within a few percent of the correct value without calibration (my brother has a Scanguage and his correction was 2% from fillups). To verify that it is not the Kiwi, I plugged it into a friend's Toyota RAV4 and verified the fuel consumption in DashCommand against his onboard fuel meter and it was dead on (within 0.1 L/100km).
So something on my Elantra is reading incorrectly, but what?
I noticed that my fuel consumption does not go down when coasting, which might explain the discrepancy. For example, earlier I was coasting down a hill, no gas, 2500RPM and it was in top gear. The fuel flow gauge said 10.5L/hour. That does not make any sense, since if I'm coasting down the hill it should be using zero or close to it.
So can someone give me the formula for how fuel consumption is calculated? Then I could watch the individual PIDs and see which one is wrong, or debug further.
Otherwise, any other suggestions for what to try??