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Old 31st May 2010, 21:31   #436
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Default Why the a/c reduces FE ?

I recently got my car/s a/c fixed after a long period of unuse.I have a tacho meter on my car(800) with a shift light marked at 3000 rpm.With and without a/c i always shift around or less than 3000 rpm mark.At that point with 4 speed tranny i hover around 70kmph w/o the a/c.With a/c it's around 60 something.I get 15 kmpl in mixed driving w/o a/c

Now given the fact that even with the a/c on i always shift at the same 3000 rpm and with the same traffic and driving conditions shouldn't i theoritically get the same FE.Now please note i have just got the a/c fixed and havent checked my FE after that.But with the same shift points and minimum idling (wherein the a/c rpm is higher) should my FE stay the same or decrease if the a/c is on.If it decreases where does the extra fuel go when the a/c is on ?
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Old 31st May 2010, 22:25   #437
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^^ The Engine needs to work harder due to the extra load due to AC compressor, Hence the lower FE.
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Old 1st June 2010, 09:55   #438
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^^ The Engine needs to work harder due to the extra load due to AC compressor, Hence the lower FE.
Yes it works hard in the sense the car pickup decreases making us want to press down harder on the gas pedal.But if i were to keep the rpm within the same limit as i would drive w/o and sacrifice speed for the sake of FE wouldn't MY FE remain the same even with the a/c on ?
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Old 1st June 2010, 12:08   #439
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No, the car needs to burn more fuel to keep the engine at the same RPM. Also, the speed at a given gear and RPM should always be the same, with or without AC. Get your clutch plates checked, from what you've stated, it appears that they might be slipping.
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Old 18th June 2010, 16:55   #440
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Originally Posted by sumeethaldankar View Post
Yes it works hard in the sense the car pickup decreases making us want to press down harder on the gas pedal.But if i were to keep the rpm within the same limit as i would drive w/o and sacrifice speed for the sake of FE wouldn't MY FE remain the same even with the a/c on ?
Fuel efficiency is a combination of engine RPM and the speed with RPM being the primary factor. So you get the best FE at a particular RPM. A higher gear at a particular RPM means greater will be the speed and hence you cover more distance by burning the same amount of fuel.

Now when you are running with AC, there is more load on the engine and thus you will pump more gas to maintain the RPM. But this particular RPM does not relate to the particular speed you achieve while driving w/o AC.

Hence you cover lesser distance even though you maintain the same RPM which will relate to you getting lesser FE.
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Old 24th June 2010, 23:24   #441
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Hi,

I have a query for which I am not able to find the correct answer. Am posting this here as this thread is related to FE.

Every manufacturer is using the term FE as an important point for marketing their cars (at least cars like alto, beat, polo, indigo etc). And the term used is ARAI figures. While in the process of booking my car, visited many showrooms of different car manufacturer, asked the sales person - can you please explain me what are the conditions used for testing, to arrive to this xkm/l or ykm/l figure for different cars. None could reply in detail, only answer got is these tests are done in " ideal " condition.

Can anybody explain what are these " ideal " conditions?
Is it the same for all cars - I mean to say is it same for hatchback, sedan, MUVs or its different for different segment?
Also, would like to know the fuel used for testing - is it normal fuel?
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Old 25th June 2010, 15:39   #442
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Maruti has announced mileage of all its cars which has been tested by ARAI (Automotive Research Association of India) Pune; VRDE (Vehicles Research and Development Establishment) Ahmednagar and ICAT (International Centre of Automotive Technology) Manesar.
These numbers are certified by government body and this number can be used to compare the mileage across any car from any manufacturer since the standard test conditions are same for all manufacturers.

About Standard Test Conditions:
The approved agencies conduct tests on all the cars under “standard test conditions”. Amongst many parameters, the “standard test conditions” include: 2 persons in the car, AC switched-off; Standard (non-adulterated) fuel; gear changes in a predetermined pattern and at predetermined acceleration levels; standard air pressure in the tyres, wind speed etc. As the “standard test conditions” during tests at the certification agency are identical for all vehicles, irrespective of manufacturer, the customer will able to make correct comparisons of fuel efficiency, across car models.

Maruti announces fuel efficiency numbers (Mileage) for all its cars - Motorcycles - Zimbio

Murthy

P.S. This list is not all inclusive but should whet your curiosity a little bit. :-)

Murthy
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Old 26th June 2010, 21:33   #443
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Thanks Murthy for the info . Yes you are right, even though still not all my queries are answered but your post have answered some of them.

I guess as there are more than 1 organization doing these kind of certifications, so there is a trade secret which are not disclosed.

May be somebody directly involved in the process or some moderators from Team-BHP may have some detailed info regarding the same as they get the invitations of driving cars pre-launch so might be....

Anyways, its just a query from myside which in anycase not going to affect our driving or neither can we simulate those conditions in our real day-to-day drive
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Old 14th July 2010, 13:23   #444
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Maruti has come out with a funny ad on TV.

The sales guy is talking about a luxary ship with it's own swimming pool ,cosy bed rooms etc and ends the sales pitch mentioning the top speed as 25 knots. The prospective buyer asks 'kitna dega?' :-)

The sales person looks stunned.

The ad ends highlighting the typical Indian mentality and assuring the customer that they have many models to satisfy the customer's needs.

The point I want to make is

it is better to keep the engine healthy by erring on the side of a lower gear than optimum rather than the reverse. The 1 km. per litre extra you may get by driving in a higher gear than optimum is not worth the risk of straining the engine constantly.

Particularly when you use A/C hundred percent keep an eye on the engine sound. If you shift to a higher gear too soon the straining will be obvious. Enjoy your drive and forget about FE.

Murthy
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Old 27th July 2010, 17:57   #445
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Default A glass of water initiative by toyota

Toyota has come up with this following methodology to get maximum mileage and track it on their website A Glass of Water - SE

Gave a try with my iphone app, but couldnt login. YMMV.
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Old 15th August 2010, 06:34   #446
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I have a stupid doubt: In a Common Rail Turbo Diesel Engine I heard the FE increases when Turbo gets activated. Turbo gets activated at around 2000RPM.

So the stupid question is does activating Turbo in lower gear by driving in higher rpm(i.e at a slightly higher speed than the required speed to shift next gear) will increase FE or decrease?
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Old 29th August 2010, 17:56   #447
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Default Mileage Issue - Qualis - GS - 2000 Model

Hi, I have a 2000 June Qualis GS (8 Seater) with center A/C blower. This is primarily driven by my wife. She gets a mileage of only about 8kmpl or so. I have had the air filter changed recently (June 2010). Is there something else that could be causing such a low mileage? I also got the same on my recent trip to Pondy on the highway, so it is not a driving issue I am guessing
The odometer has run about 94K so far and all services are done only at the Toyota authorized service center with the necessary Preventive Maintenance done as per their schedule.
Could it be the clutch? Lanson Toyota (Chennai) have told me that the clutch is due for an overhaul, but I have been putting it off since one mechanic there did tell me it is not too bad.
Thanks.
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Old 29th August 2010, 18:23   #448
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Is 8 kmpl in city or on the highway? Our Qualis gives us around 8-9 in the city and the best it has managed is around 12.5 kmpl on our Mumbai-Lonavala trip with 9 people and a/c on.
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Old 30th August 2010, 16:38   #449
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Quote:
Originally Posted by v12 View Post
Is 8 kmpl in city or on the highway? Our Qualis gives us around 8-9 in the city and the best it has managed is around 12.5 kmpl on our Mumbai-Lonavala trip with 9 people and a/c on.
It is 8Km in the city. I think I used to get 11Km earlier. Also I just filled in HSD in Pondicherry and think this has helped to some extent. Not really sure though. I plan to use HSD for a couple of months now to see if that helps.
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Old 26th September 2010, 11:07   #450
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Quote:
Originally Posted by SANSI View Post
I have a stupid doubt: In a Common Rail Turbo Diesel Engine I heard the FE increases when Turbo gets activated. Turbo gets activated at around 2000RPM.

So the stupid question is does activating Turbo in lower gear by driving in higher rpm(i.e at a slightly higher speed than the required speed to shift next gear) will increase FE or decrease?
I am curious to know the same. Is it better to move to a higher gear like in petrol, or to run in a lower gear and keep the revs high enough to be in the turbo range?
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