How do trip computers work exactly?

[Howard-]

I.e. the bit that tells you your average/instant fuel consumption, and how many miles left you have on the current tank of fuel.

Does it know *exactly* how much is left in the tank, or is measuring how much fuel is squirted into the engine, or what?

I'd appreciate a technical insight if anyone can offer it

[130R]

They don't work in my experience

[miniman]

IIRC it normally works off the airflow meter which knows how much air is going through and therefore how much fuel is needed.

[eldar]

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

[130R]

eldar said:

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

Hmm, I don't think it's the calibration because they all seem to do the same thing. Drive around slowly and they tell you that your range is 300 miles (for example), then step on the power for a bit and apparently I've covered 100 miles in 5 minutes.

[Munter]

130R said:

eldar said:

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

Hmm, I don't think it's the calibration because they all seem to do the same thing. Drive around slowly and they tell you that your range is 300 miles (for example), then step on the power for a bit and apparently I've covered 100 miles in 5 minutes.

^^^ That's not broken! That's working perfectly. As your average MPG drops your estimated range adjusts.

[Howard-]

130R said:

eldar said:

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

Hmm, I don't think it's the calibration because they all seem to do the same thing. Drive around slowly and they tell you that your range is 300 miles (for example), then step on the power for a bit and apparently I've covered 100 miles in 5 minutes.

You expect it to do 300 miles at 50MPG *and* 15MPG?

Anyway thanks guys.. How do the sensors in fuel tanks work, generally? Some sort of float sensor?

[mrmr96]

Yes, a float. Like in your toilet cistern.

[130R]

Munter said:

130R said:

eldar said:

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

Hmm, I don't think it's the calibration because they all seem to do the same thing. Drive around slowly and they tell you that your range is 300 miles (for example), then step on the power for a bit and apparently I've covered 100 miles in 5 minutes.

^^^ That's not broken! That's working perfectly. As your average MPG drops your estimated range adjusts.

I understand that but to me that makes it useless because the reading is all over the shop depending on how judicious I'm being with my right foot at the time. It's probably all right if you do a lot of motorway miles I suppose.

[Poledriver]

mrmr96 said:

Yes, a float. Like in your toilet cistern.

You've got a floater in your fuel tank!?

[mnkiboy]

130R said:

Munter said:

130R said:

eldar said:

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

Hmm, I don't think it's the calibration because they all seem to do the same thing. Drive around slowly and they tell you that your range is 300 miles (for example), then step on the power for a bit and apparently I've covered 100 miles in 5 minutes.

^^^ That's not broken! That's working perfectly. As your average MPG drops your estimated range adjusts.

I understand that but to me that makes it useless because the reading is all over the shop depending on how judicious I'm being with my right foot at the time. It's probably all right if you do a lot of motorway miles I suppose.

So basically you're saying you would like a trip computer which can predict how you are going to drive in the future? Unfortunately the technology doesn't exist to do this at present.

[eldar]

mnkiboy said:

130R said:

Munter said:

130R said:

eldar said:

130R said:

They don't work in my experience

Probably mis calibrated. The sensors and ECU are normally very accurate, so the source data is OK. The interpretation can be iffy, so displays can be out.

Hmm, I don't think it's the calibration because they all seem to do the same thing. Drive around slowly and they tell you that your range is 300 miles (for example), then step on the power for a bit and apparently I've covered 100 miles in 5 minutes.

^^^ That's not broken! That's working perfectly. As your average MPG drops your estimated range adjusts.

I understand that but to me that makes it useless because the reading is all over the shop depending on how judicious I'm being with my right foot at the time. It's probably all right if you do a lot of motorway miles I suppose.

So basically you're saying you would like a trip computer which can predict how you are going to drive in the future? Unfortunately the technology doesn't exist to do this at present.

Mercedes computers do this to a degree. Different algorithm. More accurate than the fuel gauge!

[mrmr96]

Poledriver said:

mrmr96 said:

Yes, a float. Like in your toilet cistern.

You've got a floater in your fuel tank!?

Yup, it's the black wedge shaped bit.



PS - Yes,