Yaris Verso 1.3 VVTi - data source of dashboard fuel consumption display?

[jackmilas]

In 2000 Yaris Verso 1.3 VVTi what's the data source of dashboard fuel economy display?

The average consumption (L/100km) shows consistently values that are around 1.5L off, for example real consumption is around 8L/100km and the car's display will show 6.5L/100km during the same distance driven.

I know it isn't MAF sensor because when I disconnect it it's displaying instant and average fuel economy. In fact my ODB2 iPhone app is using MAF readings for calculation and that is fully spot on with reality.

Is there a fuel flow meter somewhere in the car?

[bronsin]

No. That would be the only way to properly do it and they are$$$$. I had one of those computer mpg deals on my ST 1300 and it was a joke.

With a fuel flow device you wouldn't need a gas gauge.

[jackmilas]

What's the source of this economy display?

[CTScott]

Originally Posted by jackmilas

What's the source of this economy display?

I haven't seen the source explained by Toyota, but there are quite a few different parameters that can be used (injector duty cycle, MAF {assuming a specific AFR}, etc.) The deviations from math when doing fuel fill-ups can be somewhat due to differences in shut off point of the gas pump, but more often are due to how the standing still while running periods are handled. Theoretically your L/km is infinite every time your speed is zero.

[bronsin]

Originally Posted by jackmilas

What's the source of this economy display?

I ll take a stab at this one. I think they go by manifold pressure. I might be wrong. In any case in my experience the only accurate way to measure mpg is when you fill the tank.

[Bluevitz-rs]

Originally Posted by bronsin

I ll take a stab at this one. I think they go by manifold pressure. I might be wrong. In any case in my experience the only accurate way to measure mpg is when you fill the tank.

Manifold pressure can only be measured on cars with a MAP (Manifold Absolute Pressure) sensor. All modern toyota engine use a MAF (Mass Air Flow)