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Old 27th June 2011, 14:03   #121
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Default Re: Does coasting save fuel?

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Originally Posted by vina View Post
Are these numbers for petrol vehicle? In that case pretty good I would say.
yup Vina, these are petrol vehicle numbers.
I have a Ikon Flair 1.3.
You can look here for the mileages I have recorded during my running.
http://www.team-bhp.com/forum/long-t...ml#post2382489

Infact, MX6 or BENBSB29, has even achieved 20kmpl on the same car.
I think even Dhanushs, who regularly drives on highway gets similar mileage or even better.
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Old 27th June 2011, 14:16   #122
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Default Re: Does coasting save fuel?

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Originally Posted by vina View Post
May be the idle rpm when the car is moving with clutch engaged is sligthly lower? I mean the car acts as an "extra flywheel" even when it is going at a constant speed.
I'm not sure about it. The other reason might also be the fact that Baleno has insufficient torque at these rpms, so that the ECU is lugging the engine to reach the idle rpm, but cannot. I have never driven a baleno in these conditions. Next time, I will try it.


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Originally Posted by vina View Post
Are these numbers for petrol vehicle? In that case pretty good I would say.
If driven sedatley, I get an average of about 18.5 kms per liter of petrol (Sulthan Bathery - Bangalore), in my '07 petrol ikon. It has done ~1.1 lac kms, still the average is consistent. Even hard driving (redlining frequently) on the highway gives me ~13-14 kmpl.
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Old 27th June 2011, 19:13   #123
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Default Re: Does coasting save fuel?

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Originally Posted by dhanushs View Post
No, it would amble along at idle rpm. Another way to try this is to try and accelerate the car using idle rpm. ie, using only clutch. It would take a lot of time and patience, but still, you will be able to reach idle rpm in 5th gear.
Would this not depend on the torque available at that RMP and the load/weight that has to be carried?

As mentioned before in this thread, I am no techie, but that is what it seemed to be, based on my limited understanding.

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Originally Posted by Fordmanchau View Post
Guys, thanks to discussion here, I have been practising COASTING to save fuel.
As mentioned here,I am letting go of the A-pedal at any incline, minimised the use of brakes by slowing down ahead of traffic signal,etc. This way I managed to bump up my city mileage from a poor 7.8kmpl to a decent 10.3 kmpl. Although, all of this would not be because of new driving practices but still a fair amount of credit goes to the new technique.
It is a big change (about 32%!). Wonder what part of it could be attributed to coasting and what part to other measures you have been taking (btw, tyre pressure makes a big impact on FE).

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Other thing, I am doing is when I see a decent open stretch, straight or incline, I take the foot off the pedal and move to higher gears. Like , if I am on 2nd or 3rd, I lift my foot of the A-pedal change to 3rd, 4th or 5th gear, if there's no traffic ahead.

I have observed that this helps to maintain the momentum for a little long.
Yes, that should help. However if you were to put it into neutral, it may maintain the momentum even longer, though still keep on consuming some fuel.

It seems that coasting would put more stress on the moving mechanical parts than simply maintaining speed in the highest comfortable gear; or even from putting int into neutral.

Being in neutral may have other safety concerns, as would being in a higher gear (ample lag and taking longer to get to a lower gear as compared to from neutral), but that is a different aspect and discussion.
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Old 27th June 2011, 20:46   #124
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Default Re: Does coasting save fuel?

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Originally Posted by Fordmanchau View Post

Infact, MX6 or BENBSB29, has even achieved 20kmpl on the same car.
I think even Dhanushs, who regularly drives on highway gets similar mileage or even better.
My Ikon Flair (07 edition) used to give back 18-19 on the expressway between Pune to Bombay if kept at 2500RPM on fifth gear. This amounted to about 100kmph. Ikon cabs get over 20-21 on this stretch as they maintain lower RPM and lower speeds of 80-90km/hr. Since road is downhill, coasting is frequently employed while driving down this stretch.
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Old 27th June 2011, 22:00   #125
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Default Re: Does coasting save fuel?

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Originally Posted by Poitive View Post
It is a big change (about 32%!). Wonder what part of it could be attributed to coasting and what part to other measures you have been taking (btw, tyre pressure makes a big impact on FE).
Yes that's a big change. Apart from changing driving technique, I think it can also be attributed to open roads and longer distance that I drove in the city.But still not sure, what amount can be attributed to what reason.
The time when I got 7.8kmpl, I drove only home-office-home.

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Originally Posted by Poitive View Post
However if you were to put it into neutral, it may maintain the momentum even longer, though still keep on consuming some fuel.
Coasting in neutral is not an option, I would like to try.Besides being unsafe, it leads to higher stress on the brake pads, plus when you want to engage gears, it will be confusing on what gear to engage depending on speeds, that can lead engine stress. Nobody would stop, engage 1st gear and then start again.
IMO coasting in a higher gear would not result in additional stress to engine as lower the rpm, lower the work engine has to do.
Please excuse if I don't make any sense.

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Originally Posted by dot View Post
My Ikon Flair (07 edition) used to give back 18-19 on the expressway between Pune to Bombay if kept at 2500RPM on fifth gear. This amounted to about 100kmph. Ikon cabs get over 20-21 on this stretch as they maintain lower RPM and lower speeds of 80-90km/hr. Since road is downhill, coasting is frequently employed while driving down this stretch.
That's good to hear. yup on 5th gear, Ikon runs at 100kmph at 2.5k rpm.
at 2k rpm it is 80kmph in 5th gear. The rpm reading increases by 500 for same speeds at 4th gear.
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Old 28th June 2011, 10:01   #126
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Default Re: Does coasting save fuel?

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Originally Posted by supremeBaleno
I did not get a long enough stretch to try 5th gear, but after this experiment, I am guessing the car will still amble along at ~20kmph in 5th gear without A-input at same 400rpm or so.
Tried this yesterday and the car puttered along at ~22kmph @ 400rpm. So, my belief that petrol cars cannot keep going without A-input was proved wrong - you learn something new everyday.

BTW, this ambling along without A-input is not only at tooo slow a speed (20-22kmph), but also does not feel comfortable as it does on a diesel (eg. Punto where the speed is ~40kmph in 5th gear without accelerator input). Sort of feels like it would knock and die anytime - so serves only academic purpose.

P.S: All slow-speed driving tried on the new road under Velachery flyover connecting Velachery to GST road at Officers Academy - this road has almost no traffic - maybe cabbies and others have not yet discovered this new route.
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Old 28th June 2011, 16:00   #127
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Default Re: Does coasting save fuel?

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Originally Posted by Fordmanchau View Post
Coasting in neutral is not an option, I would like to try.Besides being unsafe, it leads to higher stress on the brake pads, plus when you want to engage gears, it will be confusing on what gear to engage depending on speeds, that can lead engine stress. Nobody would stop, engage 1st gear and then start again.
IMO coasting in a higher gear would not result in additional stress to engine as lower the rpm, lower the work engine has to do.
Please excuse if I don't make any sense.
If one is unsure of which gear to return to, one should normally choose the higher gear (also having depressed the A-pedal a bit - one would learn how much from a bit of experience). One surely doesn't need to stop and engage the first gear while returning from neutral. Have other thoughts coasting in neutral and returning back to gear, but don't find it right to get into that, as it may seem that I am advocating that. Many others who may read these posts (members or otherwise) may start to try this practice, which could be unsafe if not handled properly.

Enjoy the higher FE mate and keep us updated on your findings with driving practices.
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Old 18th November 2011, 16:30   #128
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Default Re: Does coasting save fuel?

Im badly confused on pros and cons of neutral costing. Many have quoted that during neutral coasting fuel for idling will be taken whereas when rolling in gear with no throttle, fuel flow is cut-off.

Consider im doing a downhill in 2nd gear with no throttle, would i cover up the entire distance at Zero fuel ? I believe the fuel consumption in both the cases would be the same. So the only difference will be the engine-braking advantage.

I dont think neutral coasting is to be blamed for Fuel Efficiency.

Im open for corrections

VinC
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Old 19th November 2011, 01:42   #129
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Cool Re: Does coasting save fuel?

Voila! This is new information for me, being an old school mechanical engineer lost a lot of mechanical knowledge by becoming a software nothing. I never ever thought in my wildest dreams that the fuel would be cut off at a high engine RPM. But this definitely seems viable as the 4-stroke engine need not need any lubrication from the fuel. However, what about the valves? I think they will still open and close as the timing cams are connected to the crankshaft. And imagine the exhaust producing no exhaust even when the engine runs at a high RPM!

I would definitely like to give it a try not only for downhill descents, but even for for normal braking (not in case of emergency braking, but for anticipated braking), by shifting into a lower gear at the current speed the car is running. I usually have a (bad) habit of braking my Hero Honda Splendor by shifting to lower gear than using the not so great drum brakes (moreover, I could afford this habit given its frugal drinking habits). I was always wondering if I could ever carry over the habit on a car too. Now, this thread is an inspiration. Not only that I can satisfy my bad habit, but also that I can save on precious fuel

On a descending road at a private place, ensuring that no traffic is around, I would also like to try myself a non-advisable experiment. Just for the sake of experimenting and to see any difference. Turn off the ignition key (CAUTION!-It is extremely dangerous to turn off the ignition while running as the brakes will not be working properly) while coasting in gear.

Quote:
Originally Posted by VinC View Post
Consider im doing a downhill in 2nd gear with no throttle, would i cover up the entire distance at Zero fuel ?
Going by these posts, I tend to agree with them that you will spend only close to zero fuel.
http://www.team-bhp.com/forum/techni...ml#post2390371 (Does coasting save fuel?)
http://www.team-bhp.com/forum/techni...ml#post2392914 (Does coasting save fuel?)
http://www.team-bhp.com/forum/techni...ml#post2392943 (Does coasting save fuel?)

And, to cut a long story short, you may read http://www.team-bhp.com/forum/techni...ml#post2400868 (Does coasting save fuel?).
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Old 18th February 2012, 00:19   #130
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Default Re: Does coasting save fuel?

In a IDI engine (Say, an Fiat Uno 1.7D, which doesn't have an ECU) does coasting save fuel?
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Old 18th February 2012, 10:33   #131
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Default Re: Does coasting save fuel?

Fuel saving or not, coasting is an unsafe practice. The vehicle should be in appropriate gear at all times for best control.
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Old 18th February 2012, 13:34   #132
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Default Re: Does coasting save fuel?

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Originally Posted by ramzsys View Post
In a IDI engine (Say, an Fiat Uno 1.7D, which doesn't have an ECU) does coasting save fuel?
As long as coasting consumes less fuel compared to idling, you save fuel. That would be true in the older non-ECU based engines. With modern engines the amount of fuel used while decelerating is much less than while coasting, so you do not save fuel.

Apart from not saving fuel, coasting is a bit risky as you have no control on speed (except downward with brakes), which can lead to a sticky situation in case you have to accelerate to take any evasive action.

Coasting down hill is extremely dangerous as you can easily over speed, loose control, and go off the road at turns.
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Old 12th April 2012, 15:47   #133
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Default Hill descent in neutral

Hi,

I am your average rider who slogs for most of the year and come those few wonderful days, head off to the hills. There is something which has been on my mind for some time now, so i thought i would ask:

Ever since i started riding, i was told not to descend down a slope in neutral. All i want to know if there is any basis to this, and if so, WHY?

Note From Team-BHP Support Team: Foul language is strictly prohibited on the forum, either directly or indirectly. Please avoid slang/foul language henceforth. Thank you for your anticipated cooperation.

Last edited by suhaas307 : 12th April 2012 at 20:06.
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Old 12th April 2012, 15:55   #134
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Default Re: Hill descent in neutral

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Originally Posted by bsenroy View Post
Hi,

I am your average rider who slogs for most of the year and come those few wonderful days, head off to the hills. There is something which has been on my mind for some time now, so i thought i would ask:

Ever since i started riding, i was told not to descend down a slope in neutral. All i want to know if there is any basis to this, and if so, WHY?
Without Engine braking, you only use your brakes for slowing down.
Very soon the brakes will heat up and start fading.

The idea is to use the same gear coming down as you would when going up.

Last edited by moralfibre : 9th January 2013 at 10:17. Reason: Editing quoted post.
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Old 12th April 2012, 19:51   #135
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Default Re: Does coasting save fuel?

Elaborating on bblost's last line on why exactly. We are in control of the car while in gear (read engine braking) and not at all while in neutral down the hill. By 'being in control' means we and the car are always prepared for emergency braking and acceleration. In addition, in neutral, the car tends to gain more acceleration than in gear, on downhill descends.

This holds true for a curve too. Even before entering the curve, the best practice is to reduce to the gear the car is maneuverable during and after the curve. Threads on our forum on license tests in Europe hold testimony for the same. This is in opposite to our (I guess many of us) usual practice of depressing the clutch and brake while at the curve, and downshifting at the last moment when it is absolutely necessary.
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