[Sutripta]

^^^
Definitely about the frontal area. And the seemingly ad-hoc nature of some aspects.

Is the same driving cycle used for checking for noise? Is it done in an anechoic chamber?

If a vehicle has different 'modes', will all these tests be done for every mode?

Regards
Sutripta

[SPIKE ARRESTOR]

Sutripta, which noise are you talking about, Pass by?

[Sutripta]

Originally Posted by SPIKE ARRESTOR

Sutripta, which noise are you talking about, Pass by?

Yes. Also is it some type of weighted average used. Or peak noise at a particular setting (in which case driving cycle does not matter).

Are there any regulations regarding in cabin noise?

Also, with the coming of (electronically controlled) auto GBoxes, different modes (personalities) is just a program away. Will all the tests have to be repeated for all modes.

One thing which I hoped ARAI would do was report fuel consumption as l/ 100 Km. I find that more logical.

Regards
Sutripta

[SPIKE ARRESTOR]

Pass by noise measurement is different. No regulations for in-cab noise.

[Gansbab]

Originally Posted by Mpower

How can there be a fixed drag co-eff for a Omni and a Honda City, lets say both are 900 kg?

There isn't a fixed drag coefficient to be used compulsorily. Most often manufacturers get their own coefficients (road resistance and air resistance) for different vehicles via a field test known as "coast-down".

These coefficients are then used when performing the emission test on the appropriate drive cycle. Different regions in the world have different representative drive cycles.

[Leop]

I am assuming that there is some pre defined driving cycle which would have some acceleration element in the test.
I have a small doubt on how the vehicle's engine is loaded on a road roller. If the roller is purely an inertia based roller, then this would not reflect at all with real world driving.
This is because the engine of a 1000kg car needs to accelerate a 1000kgs during acceleration. Here the engine would only need to accelerate the inertia of the roller.
Secondly this inertia would be the same for all vehicles irrespective of weight.
Roller work in a dynamo measuring engine output as we are only measuring engine output (HP/Torque).
Rolling resistance cannot be used to calculate acceleration needs.

It is possible to have some form of variable resistance (water or electrical) calibrated for each vehicle but I am doubtful if this is used.

What am I missing?

[Gansbab]

Originally Posted by Leop

I am assuming that there is some pre defined driving cycle which would have some acceleration element in the test.
I have a small doubt on how the vehicle's engine is loaded on a road roller. If the roller is purely an inertia based roller, then this would not reflect at all with real world driving.
This is because the engine of a 1000kg car needs to accelerate a 1000kgs during acceleration. Here the engine would only need to accelerate the inertia of the roller.
Secondly this inertia would be the same for all vehicles irrespective of weight.
Roller work in a dynamo measuring engine output as we are only measuring engine output (HP/Torque).
Rolling resistance cannot be used to calculate acceleration needs.

It is possible to have some form of variable resistance (water or electrical) calibrated for each vehicle but I am doubtful if this is used.

What am I missing?

For each individual vehicle (and each individual inertia classes), the inertia roller simulates the resistance in kW. The actual kW for a particular vehicle mass is determined by field test known as coast down or standard values which are given in any emission standard (Try googling Unece Reg 83, its available for free)

A particular vehicle (with its different variants) sits in different inertia classes and it is a common practice to test the worst inertia class (or one lower) for that vehicle.

Hope this clarifies your doubts.. or raises more..:P

[amit1234singla]

I am writing this to invite thoughts of fellow members if they really think that ARAI FE ratings are difficult to get in real life driving conditions?

Let me share our experience. We have three cars in the family. 2 Santros and 1 Indigo Manza QJD. The FE of both our Santros on highway w/o AC is in the range of 18-19. This is with about 2 people on board. The FE of Manza under similar conditions is 22-24. It has never been below 22 even in the first 2000 km. Now we know that ARAI ratings of Santro is about 18 and Manza is 21. So we seem to get more than that on three cars under real life driving conditions!

I know a large part of FE is dependent on driving style and we in family drive sedately (read Santros max at 90, Manza max at 110, gear shifts at right RPM, linear acceleration etc), but still aren't ARAI ratings also supposed to be under optimal driving conditions?

So in other words, based our experience, I am trying to establish that it is possible to get similar (or more) FE than ARAI in reality.

What are your views?

[Gansbab]

Originally Posted by amit1234singla

I know a large part of FE is dependent on driving style and we in family drive sedately (read Santros max at 90, Manza max at 110, gear shifts at right RPM, linear acceleration etc), but still aren't ARAI ratings also supposed to be under optimal driving conditions?

So in other words, based our experience, I am trying to establish that it is possible to get similar (or more) FE than ARAI in reality.

What are your views?

@amit1234singla

The ARAI driving cycle consists of a cycle which was formulated upon the European Driving Cycle. It consists of an urban cycle and an highway cycle and the overall FE figures are an average of both cycles.

It is easy to deduce that if most of your journey consists of steady speeds of @ 90 kmph (even better if you drive @ steady 50 kmph), it would result into a FE better than the ARAI FE as you are avoiding the urban cycle.

ARAI FE has been introduced as it gives us a better comparison between all vehicles as they essentially are driven over the same cycle.

Nice to know you get these figures, btw

[motortechie]

Is it fair to assume that a car with higher ARAI FE figure would give more mileage than a car with lower ARAI FE figure with the assumption that both the cars would be driven by the same person with same driving style under same driving conditions?

[Gansbab]

Originally Posted by motortechie

Is it fair to assume that a car with higher ARAI FE figure would give more mileage than a car with lower ARAI FE figure with the assumption that both the cars would be driven by the same person with same driving style under same driving conditions?

Technically yes!

However, practically, it would be impossible to replicate the driving conditions.
Also factors like temperature, humidity, altitude, etc. also play a role in determining the FE. So also the amount of miles/kms the vehicle has already covered.

So you can definitely say that a vehicle with ARAI FE figure of 20.0 would be better on-road than a vehicle with ARAI FE figure of 12.0. However, the closer you get the harder the comparison gets (ARAI FE-14 & ARAI FE-15). Also each individual vehicle has certain variability due to production variances and this affects the FE also.

An insight where these FE figures have come into existence. Most European countries have a vehicle tax system based on the amount of CO2 figures which are closely related to the FE figures. In India, the manufacturers are reluctant to declare the CO2 figure as our tax system is different, but they have agreed to declare the FE figures as a comparison.

[CrAzY dRiVeR]

BUMPING an old article as this has become all the more relevant now.

BHP'ians have been perplexed by the 26+ kmpl figures reported by Honda City and Suzuki Ciaz, and there have been many questions raised on how ARAI calculates these FE figures.

[opendro]

In one of the arguments I had with a friend at work, I was making this blanket statement (don't ask me how I arrived at the figure, because I felt my numbers were in the safe range from experience):

"If you are driving in a condition where the average speed is between 25 kmph and 60 kmph without aggressive throttling and braking, then your mileage figure will be around the ARAI".

So, that should remove the question of whether you are driving in city or highway or single lane or whatever. If the city crawls at an hour for a 10 km commute, ARAI figure will not help. Similarly, if you are trying to average 50 kmph in a single lane highway shared with a lot of trucks and buses, ARAI figure will not help.

What that means is that ARAI cannot give figures for all conditions, but their figures and methods are indeed real world. I don't consider Bangalore traffic that takes an hour to commute 12 km as real world, because at that pace, I will rather walk, but I do have a bicycle and thus I have been cycling since last 5 years.

[AutoNoob]

Fast forward to 2016, but one question remains in my mind. I hope this is the right place to seek opinions on that.

What is the logic of 'soaking' of vehicle at 25±5 deg C before the test? It is non-coherent with Indian conditions. In my opinion, it should be changed to higher value (e.g. 35±5 deg C) to represent real operating conditions that exist in major part of our country for most of the year.

The current test method was more of a copy-paste job from EU. And I am sure that the automotive lobby will strongly oppose any move to change this basic parameter as that will pull down the 'declared' FE figures significantly.

[MadinMumbai]

Sitting in Mumbai traffic for hours on end I begin to think that the whole ARAI milage determination system for cars is flawed. Should cars in Mumbai and Bangalore get an alternative/additional system of grading milage? Maybe like a tractor does? Litres per hour (LPH) might be a more accurate system to have alongside KMPL.

Ps, this is in jest. Lest the perpetually outraged start telling me how it’s not feasible/scientific to arrive at such a determination.