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Old 26th July 2009, 07:08   #331
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I have never figured out the passion to get an exact FE figure. And it is so dependent on many external conditions like traffic, road conditions, road surface, tyre pressures, ambient temperatures, gross weight of the car, all which are usually ignored while trying to get just one variable exactly right, the amount of fuel used.
In any case, never allow your fuel tank to go empty it can cause a lot of damage to the engine and other parts. Including the cat maybe.
Full to full is a better way of getting an approximate FE reading, that all that you need to know to be satisfied with the state of tune of the car.
And filling the car in the early parts of the day when the ambient is at the lowest is the best too.
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Old 26th July 2009, 08:31   #332
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If you are not all that worried by the accuracy, you can also check it this way - On stable ground, when your fuel guage indicates quarter tank, note down the reading. Then, fill up, say 10 litres of fuel, drive around and note down the reading when your fuel guage reaches the same quarter tank mark on stable ground again. The difference in the readings will give you the consumption for the 10lts you filled. Although this is not a very accurate method, it is indicative and in the long run, if you continue this log for a month or two, it will give you a more accurate figure !
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Old 26th July 2009, 13:11   #333
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Don't run your engine till the fuel tank is empty. It will lead to premature failure of the fuel pump, clogged injectors and even engine damage due to poor fuel feed. Also, the fuel in the tank keeps the fuel pump cool and operational. Fill up when you have a minimum of 2-3 litres left in your tank.

The full tank to full tank method is the best way to measure your FE. Try to average readings taken over a few months to get an accurate figure.
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Old 29th July 2009, 14:24   #334
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Interesting article on saving fuel - Tips to Save Gas.
60mph is about 90kmph?
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Old 29th July 2009, 15:28   #335
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Quote:
Originally Posted by triedeverything View Post
Interesting article on saving fuel. 60mph is about 90kmph?
60 m/hr is about 96 km/hr to be precise. It is an interesting article but I'm not too sure if its relevant in the Indian context as the road conditions here are very different. You get a better FE if you maintain a steady speed of 75-80 km/hr.
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Old 7th August 2009, 11:19   #336
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How much do the electricals contribute towards fuel efficiency? Can we gain any noticeable FE by avoiding horns, music system and headlights?
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Old 7th August 2009, 11:24   #337
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Quote:
Originally Posted by watashi75 View Post
How much do the electricals contribute towards fuel efficiency? Can we gain any noticeable FE by avoiding horns, music system and headlights?
Not significant.

Horn is internmittant, so that does not count.
Lights are 200W
Music system 200W (high end with amp and all)
Other extra lights etc,m = 100W
So you are losing out around 1BHP with everything all, i.e. 1%
So if you get FE of 15kmpl you will get 15.15kmpl without lights.
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Old 7th August 2009, 11:37   #338
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Quote:
Originally Posted by tsk1979 View Post
Not significant.
Thanks, that was pretty clear!
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Old 7th August 2009, 11:39   #339
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Quote:
Originally Posted by watashi75 View Post
Can we gain any noticeable FE by avoiding horns, music system and headlights?
I am sure that there will be no noticeable improvement in FE by cutting down on the use of these. The a/c is probably the main component which affects FE. There is a marginal 0.5 kmpl reduction (city driving) if I run the a/c all the time.
My Swift has 90/100 halogens and there is a very slight, almost imperceptible change in RPM when I switch them on. However, I have never seen a reduction in FE during night driving.
The horns' contribution is insignificant.
I am not sure of the music system as I run a pretty basic setup. Can BHPians who run high end systems shed some light on this?
@tsk1979, I think 1% seems to be about right.

Last edited by Roy.S : 7th August 2009 at 11:44.
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Old 7th August 2009, 11:43   #340
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Regarding AC also there is a caveat.
AC switch off will result in better FE if you drive with windows up. Windows down increases drag, and at speeds above 40-50kmph its going to have significant effect.
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Old 7th August 2009, 12:07   #341
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Quote:
Originally Posted by tsk1979 View Post
AC switch off will result in better FE if you drive with windows up. Windows down increases drag, and at speeds above 40-50kmph its going to have significant effect.
tsk1979,

Correct me if I'm wrong, but don't you have to be at higher speed (~80 km/hr or more) for this drag to have a significant effect on FE?

The reason for my query is because I drive an Alto almost every day in Bangalore with my front windows down about half and take a fairly less congested route and my speeds are ~60 - 65 km/hr and I get a very good FE of 18 - 19 km/lt

When on the highways, I usually switch on the a/c, roll the windows up as my speeds are ~85-90 km/hr.

Will be great to hear your inputs.

Thanks,
gpa
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Old 7th August 2009, 13:11   #342
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Yes, the drastic effect will come up above 80kmph, but even at 60kmph the offset with AC will be around 0.5-1kmpl (depending upon the car).
Ditto for the drag.
For example if you drive a 150BHP car, AC offset will be hardly anything, but in a 40BHP car, AC power sap will be significant.
So with the M800, AC used to make a very significant noticeable dip in performance, and consequently FE. So with an M800 you would need to be above 60kmph to get benefit of windows up viz AC.
Alto has better power than 800, but still it not a lot. therefore below 60, it will help not driving with AC.
Moreover when you have city driving you never do 60 continously, you stop at lights etc., While idling AC will lead to more fuel consumption, and you will get 1kmpl-2kmpl more in a small engined car
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Old 9th August 2009, 02:42   #343
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I have an Alto LXI. What would be the ideal speed to close the windows and start the AC? Is it 60, 70 or 80kmph, in order to arrive at the best FE?

Also, I read somewhere in the LXI manual that both the 4th and 5th gears are 'overdrive'. Does this mean that the 4th gear can perform the similar role (and similar FE) as the 5th gear?

Let me know. Thanks.
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Old 9th August 2009, 08:28   #344
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Nice thread GTO. I knew many of the tips for good FE, but not all of them. So this thread was truly useful. Also the discussions have thrown up more tips on getting a good FE. As a once-upon-a-time biker I hold FE figures to reverence as this figure tells you whether you have been a good driver and a good owner of your ride and tended well to it. Moreover, it is added fun to experiment with different driving conditions and their effects on the FE.
Cheers.
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Old 9th August 2009, 14:49   #345
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Quote:
Originally Posted by misquitas View Post
I have an Alto LXI. What would be the ideal speed to close the windows and start the AC? Is it 60, 70 or 80kmph, in order to arrive at the best FE?
As tsk1979 pointed out and in my own experience, rolling up the windows once you have crossed 70 km/hr and then switching on the a/c will ensure that you derive the best FE from the Alto.

In the city, I usually do not cross 65 km/hr and so both the front windows are down a few inches that allows a steady stream of cool air to rush into the vehicle. When on the highways however, I usually roll up the windows entirely once I cross 65 km/hr and then switch on the a/c.

Last edited by gpa : 9th August 2009 at 14:59. Reason: typo
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