[mohitk1993]

Originally Posted by amazingGuru67

I am worried because, ECU in Amaze calculates the average kmpl based on trip meter's readings only. Is this the reason why the kmpl readings are optimistic than actual real life data in tank full to tank full method?

Can any one else check and let me know if this trip meter malfunction is normal or not?

AFAIK, the MFD calculates the kmpl figures based upon the actual fuel consumption of the engine determined by the ECU. The ECU monitors the rate at which fuel is fed into the cylinders and after performing the necessary calculations, feeds the same data to the MFD. Any errors obtained is due to estimation errors which may or not be intentionally done by car manufacturers.

Even though a MFD is convenient, the best way to calculate your car's efficiency remains the tried and tested full-tank method. Do it atleast once a month and compare the figure with your MFD. A ~10% error can be considered normal, any more and you must consult your ASC.

Regarding your tripmeter readings, as they seem to be optimistic by 20%, i suggest you get the car checked at the service centre. Such a high error is not acceptable and the sensor that checks for the distance travelled certainly seems to be malfunctioning.

Originally Posted by a4anurag

I just have a few doubts on this:

1) Does tyre pressure meter readings? I mean a under-inflated or an over-inflated tyre would give you different reading?

No, the tyre or the wheel speed is not used to calculate the odometer readings. Modern cars generally come with an electronic sensor attached anywhere on the underbody of the car, which tracks the distance travelled irrespective of the direction.

However, the speedometer does calculate the speed using an electronic sensor attached to the wheels. Unlike older cars =which had a speedometer gear attached to the gearbox assembly, modern vehicles measure the wheel speed to calculate the car's speed. That is why speedometer errors start to crop up when the tyres are upsized/downsized.

[a4anurag]

Originally Posted by mohitk1993

Do it atleast once a month and compare the figure with your MFD.

I hope you meant MID.

Anurag.

[ramzsys]

Originally Posted by a4anurag

Even I tried using GPS and ELM 327 OBD II reader for checking the speeds.

Speedometer: 100 kmph,
OBD II Reader: 94 kmph,
GPS via OBD II reader: 96 kmph.

If ELM327 gives a reading consistent(94 is close to 96) with the GPS, then the car's instant/average fuel efficiency reading will be accurate.

I have checked in Ford Classic. When the meter shows 80 kmph constant, OBD port reports 75, and GPS is consistent with OBD.

I guess the speedometer error is introduced in the digital -> analog conversion.

[a4anurag]

Originally Posted by ramzsys

I guess the speedometer error is introduced in the digital -> analog conversion.

Can you please explain the statement you just made please.

Anurag.

[mohitk1993]

Originally Posted by a4anurag

I hope you meant MID.

Yes, that is correct. Thanks

Originally Posted by ramzsys

I guess the speedometer error is introduced in the digital -> analog conversion.

Even though a part of the error may be accounted due to that, speedometer errors are in general, intentionally introduced by car manufacturers for the better interest of the public. Why exactly is it done continues to be a debatable topic and its best we do not discuss it in this thread. However, I would like to let you know that it is a common practice across the globe and is carried out by almost every manufacturer. Also, the speedometer is not just the only reading to be tampered with; car manufacturers seldom calibrate the fuel gauge in such a way that it does not dip soon after filling the tank but progresses slowly, increasing its rate of movement as more fuel is burned. This is mainly done to give a false assumption to new car owners that their vehicle is giving excellent fuel efficiency figures.

Such is life .

Originally Posted by a4anurag

Can you please explain the statement you just made please.

I think he meant to say it the other way round, i.e analog-to-digital.

[ramzsys]

Originally Posted by a4anurag

Can you please explain the statement you just made please.

In previous generation, the speed is read directly from the gearbox to console via cable. Now it is from vehicle speed sensor(VSS) to the ECU, and from ECU to the Speedometer console.

So the error is introduced when the digital signal from ECU is converted to analog mode in the speedometer.

[amazingGuru67]

Originally Posted by ramzsys

So the error is introduced when the digital signal from ECU is converted to analog mode in the speedometer.

This error could lead the driver to believe that he or she had crossed the destination.

For instance, while asking for directions, if you are asked to take a left at 3km and if your trip meter reads 3km at 2.5km mark.... What would you do?

The car makers must take into consideration all such scenarios in Indian condition.

Anyways, I have decided not to believe the trip meter reading and keep my eyes and ears wide open.

[a4anurag]

Originally Posted by amazingGuru67

This error could lead the driver to believe that he or she had crossed the destination.

For instance, while asking for directions, if you are asked to take a left at 3km and if your trip meter reads 3km at 2.5km mark.... What would you do?

I keep an eye on the trip meter frequently and whenever I see sign boards mentioning the distance to and destination ad check whether they have labelled it rightly or no!

I have never got any wrong reading on the trip meters.

Example is on the Outer Ring Road it says 2 kms for a destination, the destination arrives exactly when the trip meter reads 2 kms.

Anurag.

[skyfire2892]

Just wanted to share some readings.
From my mobile through gps



From trip meter





I believe odometer is accurate.

[Jeroen]

Originally Posted by mohitk1993

However, the speedometer does calculate the speed using an electronic sensor attached to the wheels. Unlike older cars =which had a speedometer gear attached to the gearbox assembly, modern vehicles measure the wheel speed to calculate the car's speed. That is why speedometer errors start to crop up when the tyres are upsized/downsized.

Correct, so also tire pressure has some small influence

Originally Posted by ramzsys

I guess the speedometer error is introduced in the digital -> analog conversion.

The error in the digital to analog mode conversion is neglible. The error on the (analoge) speedometer is different one, and is purely input (voltage) against the swing of meter needle. A properly calibrated speedometer is perfectly capable of giving a very accurate reading, easily within 1 mph. That is if the scale on the speedometer allows you to make such a granular reading to start with.

As stated above, most, if not all manufacturers introduce an offset on the speedometer reading. Effectively they will ensure your indicated speed is a little higher than the real speed. Partly safety, but probably mostly to avoid being sued and complicated court cases.

I don't know if done here in India, but back in the Netherlands I had the speedometers of my classic cars fully calibrated.

A good way to get an idea of the speedometer error is to get onto a reasonable stretch of road, maintain a constant speed and check the speed on a GPS device againt your speedometer. At constant speed your GPS device is very accurate. Over the last couple of years on some of my more modern cars I have found that the speedometer errors are really small, compared to GPS speed. I.e. less then 2%, and that was in both Europe as well as the USA.

Originally Posted by ramzsys

So the error is introduced when the digital signal from ECU is converted to analog mode in the speedometer.

See above the error in the digital to analogue conversion is neglible.

Originally Posted by whitewing

Actually there would be no way to calibrate the GPS reading with the Speedo, since the GPS does not factor in the road topology. Imagine speeding on a spiral and if your GPS sensitivity range encompasses the spiral your effective speed would be 0!

?

This is I believe, incorrect. I assume based on your statement you believe a GPS calculates the speed based on distance covered over a time? Hence you think it doesn't factor topology in.

Fact is, nowadays, and actually for the last decade, just about every GPS device on the market measures speed through a very simple doppler phase shift methodogy. So it actually measures and calculates the speed several times per second! The display won't update that quickly though, for obvious reasons. Also, this only works well (i.e. accurately) when driving at a constant speed.

But when you're driving at a constant speed, just about any GPS device will give you a very accurate speed measurement! Typical error calculation of a GPS device using doppler measurement is below 0.2 km/h

Where your GPS unit might use distance over time is for average speed. And even here I'm not hundred percent sure if they don't use some average actual speed calculation based on the doppler measurement.

I'm not a hundred percent sure of mobile phones, but all main chipset manufacturers that provide GPS chip sets to the likes such as Garmin, TomTom etc, will have doppler capabilities built in as standard actual speed measurement.

The distance over time measure is still present in some GPS units. But typical measurement cycles are 1 second and then to interpolate a whole bunch of this 1 seconds burst of data So topology is not a factor.

If you want to know a bit more and like to understand the theory and the math have a look here: http://www.gps-results.com/GPS_Speed.pdf

Jeroen

[deepclutch]

I have bought a new Ritz and it has MID showing current fuel economy and overall average fuel economy. the problem is with the average fuel economy displayed. it was showing 17-18kmpl earlier and suddenly it started showing 0.6kmpl and during a 1200kms running time, the reading grows up to 5.8kmpl. I believe this is a issue with the MID. showed it to MASS, and the service advisor reset the overall kmpl using two knobs. then, it started showing 13-14kmpl now.
What is the cause? should I ask for warranty replacement of the instrument cluster or is it some other reason that causing this fault. I am not sure, whether the average fuel efficiency displayed will again start showing wrong reading.

[deepclutch]

I have a July 2013 Ritz VDI and completed around 4000kms now. the AVG(average) fuel consumption displayed was correct for the first 500kms or so. the AVG is shown in kmpl. later, I found the display shows wrong average value resets to 0.5kmpl or such absurd values and during a period of 500kms or more running it grows up to show 5.8kmpl IIRC.

now, this happened twice resetting to 0.x kmpl value during the first 2000kms running.

reported it to Popular maruti,Muvattupuzha. after a reset, it shows the mileage correctly for sometime and then the AVG mileage doesn't seems to update and kept going down in number. while the instantaneous mileage is properly displaying seeing the values, It is verified that the AVG value is wrong. if I drive through a straight highway at 70-80kmph, even then the value shown is 15.x kmpl after the reset done at MASS. the earlier value when the car was new was 18-19kmpl value with AC. though the AVG value after the reset never showed 0.x kmpl as of now.

at MASS, they claimed to have checked with OBD scanner and doesn't find anything wrong with ECM. can some experts share some lead to what needs to be checked for confirming this problem as I find it hard to convince the service people about this issue although they acknowledge the value when I gave the car for inspection was 3.8kmpl AVG fuel consumption.

is the average fuel consumption in Ritz measured as per Trip meter or Odo meter value? I frequently reset Trip meter to count the distance for each trip.

what controls the MID of Ritz to display these values? I presume it is ECM. if so, is this needs a thorough checking up of ECM? or is there some sensors that is malfunctioning. please guide as I am total rookie in this regard.


@Moderators: Hope this is the correct section.

[sauravdc]

Originally Posted by deepclutch

I have a July 2013 Ritz VDI and completed around 4000kms now. the AVG(average) fuel consumption displayed was correct for the first 500kms or so. the AVG is shown in kmpl. later, I found the display shows wrong average value resets to 0.5kmpl or such absurd values and during a period of 500kms or more running it grows up to show 5.8kmpl IIRC.

now, this happened twice resetting to 0.x kmpl value during the first 2000kms running.

reported it to Popular maruti,Muvattupuzha. after a reset, it shows the mileage correctly for sometime and then the AVG mileage doesn't seems to update and kept going down in number. while the instantaneous mileage is properly displaying seeing the values, It is verified that the AVG value is wrong. if I drive through a straight highway at 70-80kmph, even then the value shown is 15.x kmpl after the reset done at MASS. the earlier value when the car was new was 18-19kmpl value with AC. though the AVG value after the reset never showed 0.x kmpl as of now.

at MASS, they claimed to have checked with OBD scanner and doesn't find anything wrong with ECM. can some experts share some lead to what needs to be checked for confirming this problem as I find it hard to convince the service people about this issue although they acknowledge the value when I gave the car for inspection was 3.8kmpl AVG fuel consumption.

is the average fuel consumption in Ritz measured as per Trip meter or Odo meter value? I frequently reset Trip meter to count the distance for each trip.

what controls the MID of Ritz to display these values? I presume it is ECM. if so, is this needs a thorough checking up of ECM? or is there some sensors that is malfunctioning. please guide as I am total rookie in this regard.


@Moderators: Hope this is the correct section.

Hello,

You are not alone to be bugged by this problem. We all are.
Best way is to go tankful to tankful method. last 8300 kms I am plagued by the same problem. MID shows 12-13 immediately after a tankful reset. Then it moves up to 16, 17, even gone up to 19/20 sometimes if I have driven on empty roads within 50-70 kms of reset. Then as I drive more in city, it comes down again to 17, 16, 15, 14 as the fuel finishes. Even I got the MID checked after 2000 kms and a few tankfuls. All is well - I was told.
On the forum we have discussed it under fuel efficiency sections and found a general thumb-rule. Allow a difference of 1.5 to 2 kms on the MID on the lower side. If MID shows 17.2, your tankful method will return around 15.8 (say).
Last to last tankful I did was at 7790 and drove till 8250 and tank filled. MID showed 17.4 and actual after last tankful was 16.4 (460 kms in 28lts).

Don't worry, the car is fine ...

Regards,
Saurav

[latentpotential]

Have you tried a simple car reset? Disconnect the battery for a few mins.
Since you have a VDi, you can invest in a 500-1000 Rs OBD scanner as well and track the fuel consumption being reported on your phone as well. Perhaps this may help in indicating the reason behind the fluctuation.
Last, you say the reading drops sharply at 500 on the tripmeter. Why not set the tripmeter, use the car till 490 or so, and then drop in at the MASS to show them the issue? Might be a one off bug in your car.

[deepclutch]

well, I will try without resetting trip meter for 500kms or more to see if the problem is related. however, chances are less likely.
meantime, in a new Dzire my bro-in-law, the AVG average mileage is shown correctly irrespective of trip meter settings.