[camchennai]

[b]How accurate is Multi Information Display (MID)

Most of the today’s C-segment cars comes with a multi information display(MID) and some manufacturers call it as Driver Information System(DIS), now the question is how accurate is MID or DIS??

What is MID?

Multi information display will provide information about your car and the information varies on car to car depending upon the price you pay for the vehicle. The below details are commonly found on a MID and the information would increase as you pay more for your car.

• Average fuel consumption
• Instantaneous fuel consumption
• Travel time
• Average speed
• Distance covered

How does it work?

MID is connected directly to vehicles ECU and it transmits information to the LCD display in front of the dashboard.

Now my question:- How accurate is the information displayed on the MID??

Why am I asking this question?

I am driving Toyota Camry for the past 6 months and I was under the impression that the information provided on the MID were accurate up to 95%, however in one of my recent trips I found there was a significant difference in actual fuel consumption and the one which was displayed there. As per MID, fuel consumption was 8.2L/100 KM which literally means mileage is 12 KM/L. However when I checked by filling the tank once again I saw the actual mileage to be 10.5 KM/L. This kind of a vast difference happened only on this trip which makes me write this post and creating lot of ambiguity about MID. Also, please let me know if i need to consider only partial information from the multi information display.

P.S. Distance covered – 540 KM which comprises of the below.
Ghat drive – 100 km
Plain drive – 400 KM (Average speed of 180 was maintained for about 180 KM).
City drive – 40 KM (Average speed of 25-40 KM/hr)

Now Guru’s please let me know the accuracy of MID and how far I can trust MID in future. kindly throw your light in this thread

Also, you can post on the accuracy of your car's MID

[supremeBaleno]

I would take the FE figures from the MID with a load of salt.
I drove a Punto_D for 3 days and the instantaneous figures ranged from 10kmpl to as high as 45kmpl. The latter was got when I was in top gear and take my foot off the A-pedal to slow down without braking, due to a signal coming up for eg.

If you want to know the actual FE of your car, do a fulltank-to-fulltank method.

The instantaneous FE figures could atbest serve as a way to improve your driving. For eg. the high FE shown when you ease off the A-pedal when in high gear, is in sync with the fact that fuel is cutoff completely in this scenario. So, this is a better way to approach a signal/toll booth than say coasting in neutral, where minimum fuel would be supplied.

[camchennai]

Well, the figure i have mentioned in my post were not from instantaneous fuel consumption, It was actually from average fuel consumption. I am aware that every second instantaneous fuel consumption as per driving habit however average should not be the same case right?
Full tank method is classical and exact way of finding the fuel economy, then why are manufacturers portraying this MID as a feature when the information it provides are incorrect and misleading?
Please share how are your average fuel consumption figures and what is its accuracy?

[GTO]

There's only one way to know your car's true fuel consumption : Full tank of fuel (and I mean, FULL), drive it a couple of hundred kms and then, full tank of fuel again. There really is no other way. Even better, repeat the full tank to full tank circle a couple of times, and then average the FE out.

[AbhiJ]

The CRV's MID shows instant fuel avg and the fuel avg since last trip reset...

The figure is usually optimistic by around 10%

[itsprak]

Not just the MID, even the speedometer / odometer readings are not always accurate. I have a GPS device which indicates the vehicle speed, average speed, distance traveled etc. Since the metrics indicated by the GPS are based on satellite signals, we can assume those to be the accurate actual metrics.

I have observed that speed indicated in the speedometer is always more than what is indicated in the GPS and also the difference between the two increases with speed. The difference is almost around 5 KMPH to 10 KMPH when driving at more than 100-110 KMPH. I have also observed that the distance traveled indicated in the odometer differs quite a bit from what is indicated in the GPS.

Hence the details like average speed, fuel efficiency etc shown in the MID which is entirely based on the metrics collected from the vehicle can possibly not be 100 % accurate. I would assume that if a car has inbuilt GPS unit and if the MID gets its data from the GPS unit, then the MID would be more accurate.

[camchennai]

Well your point is right, all stock speedometers will have some speedo errors and it would increase if you upsize the tire. However how do you say that whatever GPS says is right? Is it because it uses advance technology over the car?
If we you say metrics collected from the vehicle (i.e. ECU) are wrong then information from GPS cannot also be true, they are also prone for errors. No offence please.

[DerAlte]

Originally Posted by camchennai

[b]How accurate is Multi Information Display (MID)
... However when I checked by filling the tank once again I saw the actual mileage to be 10.5 KM/L. ...

LOL You compared with how much you filled? Apples to oranges comparison, to say the least.

Just think - you are comparing the accuracy of fuel consumed WITHOUT an ACCURATE reading of petrol consumed. How sure are you that the level where you filled petrol before the trip (possibly 'full tank'; trip meter at 0) is the same as that when you filled after the trip (trip meter at say X km.)??? Only if these 2 levels were the same down to a couple of mils is your assumption about the volume of petrol consumed correct.

On the other hand, MIDs in modern cars report consumption figures calculated by the injection ECU (there are lots of ECUs in a car like Camry). The injection ECU calculates petrol consumed by summing up injection time from EACH injection. The injection time is how long the injector was kept open for 1 stroke; rail pressure is assumed constant. Total Injection Time, multiplied by the reference volume / unit time (calculated in the vehicle test lab using ultra-accurate instruments), gives the petrol consumed over a period of time. Divide the distance traveled during the same time (this comes from the transmission) by the petrol volume, and one gets the 'X litres / 100Km.' figure.

The petrol consumed as measured by the ECU is accurate down to microlitres. Your measurement has a potential inaccuracy of 2 digit milliliters at least! So which method is more accurate?

[camchennai]

Sorry, I am confused.
First let me explain how did I calculate manually, I filled up the tank and reset the trip meter and MID. So on refill to tank full, consider my tank took 50L and Km done was 550KM. Now i divided the 550KM by 50L. Am I so far right?? And by this means I got as 10.5 KM/L.

Now coming back to your explanation about MID, it was more technical and I was able to understand to some extent. And my understanding says MID should be right, correct me if i am wrong.

[gavinimurthy]

The distance travelled indication given by the GPS from point A to point B is given assuming that the plane is same. Suppose you are driving uphill on a steep gradient and if the actual road distance is 1 Km, your GPS may show as 0.6 Km.

Similarly when you travel through lot of winding curves the GPS reading and the actual distance travelled won't match.

The distances mentioned on the 'mile stones' are accurate. Compare your MID figures with those. They should match closely.

Murthy

[DerAlte]

Originally Posted by camchennai

... explanation about MID, it was more technical and I was able to understand to some extent. And my understanding says MID should be right, correct me if i am wrong.

Extremely sorry, I didn't mean it to be so technical that it cannot be understood. Yes, as you have said, MID trip average reading should be correct. I am not sure (you must read the car manual) whether the average was for the trip, or for the last few km. Usually the indication is running average, i.e. the 2nd case. I may be wrong!

I was only trying to point out that in 'full tank to full tank', volume is true only if you fill from a filling station whose nozzle automatically stops, or they fill to the brim till fuel spills (I don't like the 2nd method). Even then there is an element of error in the fuel which is much larger than possible error in MID reading.

Those who don't have an MID (like me, for example) use the method that you have used. I do the same as you do - reset the trip meter on one 'full tank', calculate at the next 'full tank' fill, and as GTO pointed out, I average over a couple of fills to average out the error.

[shuvc]

Originally Posted by DerAlte

I was only trying to point out that in 'full tank to full tank', volume is true only if you fill from a filling station whose nozzle automatically stops

I normally use this method at the same filling station and with the same nozzle for that matter.

My observation has been that the mileage indicated by the Civic MID is 1 to 1.5 kmpl above what I calculate on a tankfull-tankfull basis. Everytime, without fail for 19 top-ups over the last 6 months.

I wonder if manufacturers tweak the readings intentionally. Most users will go by the MID and hence will spread the word about the fantastic FE their car is returning.

[camchennai]

Originally Posted by DerAlte

Extremely sorry, I didn't mean it to be so technical that it cannot be understood. Yes, as you have said, MID trip average reading should be correct. I am not sure (you must read the car manual) whether the average was for the trip, or for the last few km. Usually the indication is running average, i.e. the 2nd case. I may be wrong!

I was only trying to point out that in 'full tank to full tank', volume is true only if you fill from a filling station whose nozzle automatically stops, or they fill to the brim till fuel spills (I don't like the 2nd method). Even then there is an element of error in the fuel which is much larger than possible error in MID reading.

Those who don't have an MID (like me, for example) use the method that you have used. I do the same as you do - reset the trip meter on one 'full tank', calculate at the next 'full tank' fill, and as GTO pointed out, I average over a couple of fills to average out the error.

Thanks for clearing my doubt, the average which MID displayed was for this particular journey only as I have reset both MID and Trip meter post tank fill. There is a separate option to see running average .

[GTO]

Originally Posted by camchennai

First let me explain how did I calculate manually. So on refill to tank full, consider my tank took 50L and Km done was 550KM. Now i divided the 550KM by 50L. Am I so far right?? And by this means I got as 10.5 KM/L.

You need a calculator . 550 / 50 = 11 kpl.

[Trust_In_Thrust]

I have seen the MID on fiats to be very accurate while that on the city was vague and nowhere close to real figures.
MID will be more close to real figures when the instrumentation and processing information calculated from various methods like the injection cycles etc is done using more sophisticated hardware (read more expensive) .

There is no other way .If anyone has do post it here maybe we can use it in industries also .My clients would be happy saving money on just to calculate how much is going through , consumed etc.

Thanks