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View Poll Results: What percentage accuracy do you get comparing MID to Tankful to Tankful Method
99% & above 0 0%
97% to 99% 4 16.67%
94% to 97% 2 8.33%
90% to 94% 7 29.17%
Below 90% 4 16.67%
Never Checked 7 29.17%
Voters: 24. You may not vote on this poll

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Old 10th November 2012, 14:04   #61
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Default Re: How accurate is Multi Information Display (MID)

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Originally Posted by DerAlte View Post
LOL @arindambasu, in traditional accounting (in vernacular), the difference is explained away as 'baki deemak kha gai' (termites ate the rest)!!!
He he, good one. However, I find 12-14 about decent for a 1.2 mill in crazy Bangalore traffic, and hence not too many complaints.
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Old 10th November 2012, 16:30   #62
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Quote:
Originally Posted by Jeroen View Post
On the odo meter, that is calibrated to err on the safe side.
So whatever error it has, that will go directly into the MID as well. The MID can of course be calibrated/ajdusted as well.

My experience with MID is that when it comes to MPG calculations they tend to hover around a 10% error. And again are calibrated to show the error on the safe side. So their reading tend to be 10% to high.

Jeroen
My point is that even for manual calculation, we are depending on the same odometer. So, the same error will repeat there as well. So, inspite of that why is the MID on the positive side always ?

Quote:
Originally Posted by Jeroen View Post
I have no explanation on the 40% discrepancy, other than what has been suggested by others already. If you get that sort of discrepancy consistently I think you have a faulty MID system. Very rare for the MID itself to be broken. In most case it's a sensor or a cable.
We'll be doing one more trip ourselves and then we'll take the car to Hyundai service for a check-up.

Quote:
Originally Posted by DerAlte View Post
Agree that "40% discrepancy" will not go unnoticed by customers, but have such large discrepancies been reported anywhere, other than by you?
ok, so the consensus is that
1) This particular case might be a one off case where the MID or any other parts in the car is faulty.
2) MID mileage = "Tankfull mileage" +
Mileage loss due to vaporization +
Mileage loss due to error in fuel dispenser measurement +
Mileage loss due to any leaks due to over fill +/-
Mileage loss/gain due to the tank full errors on each fill-up

And just for the sake of knowledge, how much of a loss due to vaporization is acceptable for you per day on a half tank full vehicle parked in the sun at 35 degrees for the whole day ?
What I'm concerned is - if there is a considerable loss due to vaporization of the fuel because the tank is not air tight or for any other similar reason, then we can think of ways to negate that effect.

Thanks for all the responses.

Quote:
Originally Posted by DerAlte View Post
The 'odometer' is not used for measuring distance traveled and speed, it is only a display. There is a sensor whose output is used for calculating distance traveled and speed. MID gets information over CAN bus. One can check this with an OBD2 setup, which will display whatever CAN is conveying. Might be worthwhile for you to do that.
yeah, my point is that the odometer and the MID gets the data from the same place. Hence, any error purposefully induced by the manufacturer to be on the safe side of speed limit should reflect the same way on the manual calculation as well as on the MID calculation of mileage.

Quote:
Originally Posted by arindambasu13 View Post
However, I find 12-14 about decent for a 1.2 mill in crazy Bangalore traffic, and hence not too many complaints.
The thing which is of interest to me is why there is a variation in the first place and not whether the mileage of the car is good or not.

Last edited by amalji : 10th November 2012 at 16:33.
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Old 15th November 2012, 11:28   #63
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Default Re: How accurate is Multi Information Display (MID)

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Originally Posted by amalji View Post
... how much of a loss due to vaporization is acceptable for you per day on a half tank full vehicle parked in the sun at 35 degrees for the whole day ?
What I'm concerned is - if there is a considerable loss due to vaporization of the fuel because the tank is not air tight or for any other similar reason, then we can think of ways to negate that effect. ...
Theoretically none - it is a closed system since Euro / Bharat / ... emission control standards mandate that. Vapor loss is included in emissions.

Diesel vapor losses are anyhow less than petrol at normal atmospheric temperatures.
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Old 15th November 2012, 12:49   #64
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Default Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by DerAlte View Post
Theoretically none - it is a closed system since Euro / Bharat / ... emission control standards mandate that. Vapor loss is included in emissions.

Diesel vapor losses are anyhow less than petrol at normal atmospheric temperatures.
Plus, isn't the 'vaporization loss' an old concept, applicable to older vehicles? The new ones are built to rectify these as well.

As mentioned in the above quote, the loss should be negligible.
Or to put in other way, this particular loss can be considered very negligible compared to the loss in efficiency due to factors like wear and tear, friction, braking, resistance due to drag etc.
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Old 15th November 2012, 13:27   #65
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Default Re: How accurate is Multi Information Display (MID)

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Originally Posted by sarathlal View Post
Plus, isn't the 'vaporization loss' an old concept, applicable to older vehicles? The new ones are built to rectify these as well.
...
Or to put in other way, this particular loss can be considered very negligible compared to the loss in efficiency due to factors like wear and tear, friction, braking, resistance due to drag etc.
Well, it is a concept, whether old or new. Older vehicles, before Bharat Stage 1 appeared on the scene, didn't have to comply - though all such cars *were* provided with sealing filler caps.

We were discussing FUEL EFFICIENCY (MID-reported v/s calculated by user) here - didn't quite understand the context of your reference to "loss in efficiency due to factors like wear and tear, friction, braking, resistance due to drag etc."!
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Old 15th November 2012, 13:52   #66
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Default Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by DerAlte View Post
We were discussing FUEL EFFICIENCY (MID-reported v/s calculated by user) here - didn't quite understand the context of your reference to "loss in efficiency due to factors like wear and tear, friction, braking, resistance due to drag etc."!
@amalji was referring to a formula to calculate MID value, in which the factor of fuel lost due to vaporization is taken as one of the parameter.
What i meant by that statement is, that particular vaporization loss factor can be ignored for the calculation as it is of negligible value, even smaller than the factors i noted there.
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Old 15th November 2012, 13:57   #67
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Default Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by sarathlal View Post
... that particular vaporization loss factor can be ignored for the calculation as it is of negligible value, even smaller than the factors i noted there.
A-ha! Yes you are right, it is negligible.
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Old 16th January 2013, 19:25   #68
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Question Re: How accurate is Multi Information Display (MID)

Just wanted to give an update on the Verna mileage on MID.

On repeated tests, we have found that the MID average mileage exceeds tankfull to tank full mileage by > 2.5 kmpl always. There has to be a reason for that. But, we are not sure what it is ( Assuming that the ECU measures the fuel flow precisely )

I decided to continue the test on my Etios using OBD2 BT Adapter and Torquepro android app (Toyota Liva Diesel : Test Drive & Review)

How accurate is the Multi-Information-Display (MID)?-topost_mileage_error.jpg

Average KMPL for the trip is shown as 15.9 kmpl ( for 7.91 kms @ average speed of 33.4 kmph )

Fuel used is shown as 0.10 gallons ( 0.378541 litres ) which contradicts with the average KMPL!

If fuel used is correct, then the average KMPL should be 7.91/0.378541 = 20.90 kmpl
So, either the fuel usage is wrong ( more likely since I was driving in the city ) or the average KMPL is wrong.

I'm curious about the root cause of this discrepancy. Any insights ?
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Old 17th January 2013, 08:04   #69
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Default Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by amalji View Post
Average KMPL for the trip is shown as 15.9 kmpl ( for 7.91 kms @ average speed of 33.4 kmph )

Fuel used is shown as 0.10 gallons ( 0.378541 litres ) which contradicts with the average KMPL!

If fuel used is correct, then the average KMPL should be 7.91/0.378541 = 20.90 kmpl
So, either the fuel usage is wrong ( more likely since I was driving in the city ) or the average KMPL is wrong.

I'm curious about the root cause of this discrepancy. Any insights ?
I think this is just way to short of a trip to get an accurate reading. The biggest inaccuracy is probably the fuel used. I just don't think it is capable of measuring such small quantities accurately. Increase the sample, i.e. drive a much longer distance.

Jeroen
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Old 25th January 2013, 23:30   #70
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Post Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by Jeroen View Post
I think this is just way to short of a trip to get an accurate reading. The biggest inaccuracy is probably the fuel used. I just don't think it is capable of measuring such small quantities accurately. Increase the sample, i.e. drive a much longer distance.

Jeroen
@Jeroen - The discrepancy between fuel used and average mileage always exist irrespective of the distance. The one posted was just a sample. What I'm concerned about is if the ECU detects the fuel used as what has been shown, how does it calculate an average KMPL which is not aligned with the ECU's own fuel consumption calculation. More than the accuracy, what I'm concerned about is the logic used by ECU to calculate average mileage.

In layman's perspective, it's simple mathematics. Get the
distance covered,
fuel used
divide the distance covered by the fuel used and you get average mileage.
Unfortunately, the ECU seems to be using some other logic for average kmpl

On a different note, regarding the accuracy of MID, @DerAlte says it's precise.

So, there are 2 points that I'm trying to discuss here.
  1. The Average kmpl calculation algorithm used by ECU
  2. The accuracy of the fuel flow sensors
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Old 26th January 2013, 00:06   #71
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Default Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by amalji View Post
So, there are 2 points that I'm trying to discuss here.
  1. The Average kmpl calculation algorithm used by ECU
  2. The accuracy of the fuel flow sensors
It's all down on how the fuel is measured. I know on some cars there might real fuel flow sensors. However, on most, the trip computer uses the theoretical amount of fuel used by the engine. The trip computer gets input on the number and duration of the fuel injection pulses. I believe there are some other methods as well, but essentially they are all indirect measurement. e.g. it derives the amount of fuel used from a theoretical model. The amount of fuel injected is not necessarily linear with the duration of the pulse. Engine loading, fuel pressure etc will all play a role. I'm no expert, but they probably use an approximate or simplified model to calculate the fuel injected. So that introduces an error by itself.

Either way, the lower volume you try to measure the bigger the error. Just like you did, I took various readings of my Jaguar XJR trip computer. I seem to recall its fuel usage was always of by approx 10% more than actual.

Jeroen
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Old 26th January 2013, 00:33   #72
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Question Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by Jeroen View Post
It's all down on how the fuel is measured. I know on some cars there might real fuel flow sensors. However, on most, the trip computer uses the theoretical amount of fuel used by the engine. The trip computer gets input on the number and duration of the fuel injection pulses. I believe there are some other methods as well, but essentially they are all indirect measurement. e.g. it derives the amount of fuel used from a theoretical model. The amount of fuel injected is not necessarily linear with the duration of the pulse. Engine loading, fuel pressure etc will all play a role. I'm no expert, but they probably use an approximate or simplified model to calculate the fuel injected. So that introduces an error by itself.

Either way, the lower volume you try to measure the bigger the error. Just like you did, I took various readings of my Jaguar XJR trip computer. I seem to recall its fuel usage was always of by approx 10% more than actual.

Jeroen
@Jeroen - That seems to explain why the MID value is always inaccurate compared to tank full to tank full. But what about the discrepancy in fuel used and average KMPL. Logically, if the ECU gets "kms covered" and "fuel used", simple division is all that is needed to calculate average kmpl. Why doesn't fuel used and average kmpl co-relate ?
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Old 26th January 2013, 07:27   #73
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Default Re: How accurate is Multi Information Display (MID)

Quote:
Originally Posted by amalji View Post
@Jeroen - That seems to explain why the MID value is always inaccurate compared to tank full to tank full. But what about the discrepancy in fuel used and average KMPL. Logically, if the ECU gets "kms covered" and "fuel used", simple division is all that is needed to calculate average kmpl. Why doesn't fuel used and average kmpl co-relate ?
I don't have an answer for that. I can imagine that they put some sort of weighed average calculation in to keep fluctuation in average kmpl reasonable stable at first in order to overcome the inherent greater in accuracies at first. As you drive further that gets dialed out slowly.

But it seems in this case the math never works, whether it's a short or a long distance driven.
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Old 28th January 2013, 12:33   #74
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Default Re: How accurate is Multi Information Display (MID)

On the Honda Jazz 1.2L, the MID is definitely optimistic by 2-2.5 kms on the highway and about 1-1.5kms in the city. That is to say if it's showing 14.5 in the city, realistically it's 13 and on the highway if it's showing 18.5 it's in fact 16!

So the answer to the question - Not accurate.
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Old 9th April 2013, 08:26   #75
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Quote:
Originally Posted by amalji View Post
I decided to continue the test on my Etios using OBD2 BT Adapter and Torquepro android app (Toyota Liva Diesel : Test Drive & Review)

Attachment 1039487

Average KMPL for the trip is shown as 15.9 kmpl ( for 7.91 kms @ average speed of 33.4 kmph )

Fuel used is shown as 0.10 gallons ( 0.378541 litres ) which contradicts with the average KMPL!

If fuel used is correct, then the average KMPL should be 7.91/0.378541 = 20.90 kmpl
So, either the fuel usage is wrong ( more likely since I was driving in the city ) or the average KMPL is wrong.

I'm curious about the root cause of this discrepancy. Any insights ?
I made one mistake in the calculation. The Gallons used by Torque pro by default is "Imperial Gallons" not "US Gallon". So, there is a small correction.
Average KMPL for the trip is shown as 15.9 kmpl ( for 7.91 kms @ average speed of 33.4 kmph )
Fuel used is shown as 0.10 gallons ( 0.454609 litres ) which contradicts with the average KMPL!
If fuel used is correct, then the average KMPL should be 7.91/0.454609 = 17.40 kmpl

There is still a 1.5 kmpl difference between average kmpl shown on Torque pro and manual calculations of average kmpl based on fuel used shown by Torque pro.

To Do

Will try out tank full to tank full mileage on a single long trip and will validate that with average kmpl and fuel usage data by torque pro.
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