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Old 13th October 2010, 18:03   #226
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If the signal is long, then I also pop it into N so that both me and car can relax. Like someone mentioned, N is only 1 nudge away. If there is a mild slope you need to feather the brake pedal (or just rest your foot on it)whereas in D, you need a firm push on it. If its flat, then nothing is required.

N has the lowest engine drag closely followed by P.

In D mode, there is a lot of drag on the engine because there is a clutch slipping there in order to provide instantaenous take off capability.

In the future, you can expect cars to automatically switch from D to P/N at signals to save fuel.
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Old 13th October 2010, 18:06   #227
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Originally Posted by proton View Post
NEVER engage Park at the lights! More often than not one uses the box in the D or N and believe me buddy if you are not paying attention and have shifted to the P on a light, its really very possible that one shifts to R and thinks its a D and goes crashing into the rear. Its happened to many of us.
I'd like you believe you buddy, but many countries have laws against keeping the engine in idle beyond 1-3 minutes. It is suggested to switch off the engine, which should be done only in P.
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Old 13th October 2010, 18:37   #228
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I'd like you believe you buddy, but many countries have laws against keeping the engine in idle beyond 1-3 minutes. It is suggested to switch off the engine, which should be done only in P.
I regularly switch off the engine in N (on traffic lights). Any disadvantages of that?
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Old 13th October 2010, 18:55   #229
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@ samurai / guna -

Folks, I was only talking from simply a 'common sense' standpoint.
Did not read through any authorative sources as yet to claim my theory. It is very simple, if the car is doing its bit to actually move mass (and not merely stand still) - there is more power being generated and used, which will be at the cost of fuel and nothing else. This is what happens in D mode (and not in N mode).

Btw, i read thru Khangs FAQ. It talks about wear and tear of parts and not Fuel consumption. But it is a good insight into internal operation of slushbox if correctly mentioned. Thanks.

I dont recollect but even the Santro's owner manual was recommending to move to N at stops / signals. I guess proton has put in some information in this regards.

@Proton,
if you could also share the source of the information you put up.)

Last edited by jigbarai : 13th October 2010 at 18:59.
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Old 13th October 2010, 18:57   #230
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I regularly switch off the engine in N (on traffic lights). Any disadvantages of that?
How will you start it without moving back to P?
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Old 13th October 2010, 18:58   #231
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Lots of posts mentioning wear and tear of brakes when depressed while car is stopped in D. Car is not moving. Why should there be any 'wear and tear' then?

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N has the lowest engine drag closely followed by P.
Why? Isn't P same as N with a pawl activated?

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Old 13th October 2010, 19:12   #232
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Originally Posted by Sutripta View Post
Lots of posts mentioning wear and tear of brakes when depressed while car is stopped in D. Car is not moving. Why should there be any 'wear and tear' then?
Exactly.

Being in D with brakes applied is not the same as being in 1st gear in manual transmission with brakes applied. The engine is not really fighting the brakes, it would stall if that was the case.

There is a torque converter in auto-transmission. The exact working of TC is beyond the understanding of most of us, including me. But it doesn't fight the brakes when the accelerator pedal is left alone. Even a slight pressure on the brake can keep the car from moving. Only if you press the A-pedal with brakes applied, it will fight the brakes.
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Old 13th October 2010, 19:36   #233
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Quote:
Originally Posted by Samurai View Post
. The engine is not really fighting the brakes, it would stall if that was the case.
No, it is, no matter how slight. To be paid for in terms of fuel.

What I meant was that when stationary, there is no relative motion at the pads/ liners. So what wear and tear?

Another thought. Looong back (1970s) some small company wanted to introduce a system similar to MMs micro hybrid, but could not because the laws in most of the states then expressly forbade switching of the engine at traffic stops.

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Old 13th October 2010, 19:53   #234
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Quote:
Originally Posted by Sutripta View Post
No, it is, no matter how slight. To be paid for in terms of fuel.
The engine is on, so fuel will be spent.

Quote:
Originally Posted by Sutripta View Post
Another thought. Looong back (1970s) some small company wanted to introduce a system similar to MMs micro hybrid, but could not because the laws in most of the states then expressly forbade switching of the engine at traffic stops.
Now they have changed their mind. In New Jersey, it is illegal to idle for more than 3 minutes.

NJDEP - www.StopTheSoot.org
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Old 13th October 2010, 19:53   #235
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Quote:
Originally Posted by Sutripta View Post
Why? Isn't P same as N with a pawl activated?
Good question but that's what I've heard. Dunno the exact details but I guess its one other clutch engaged in P. Could be different in some cars. In my car, procedure to check fluid level is in N with engine running. That tells me its not quite the same as P.

As far as the brakes, yes wear is nil if there is zero relative motion between pad and rotor but usually there is some motion because most of us are not focused on keeping a firm foot n the pedal and tend to move an inch here and inch there.

But in general AT cars have more pad wear because we tend use to brake to control the car's progress (in D) when crawling in traffic rather than the gas pedal.
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Old 13th October 2010, 19:59   #236
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Well if it is a longish signal, I do shift the car into N and keep my foot on the brakes. 1 reason is I have to keep the brake pedal pressed less than with the car in D. And the 2nd reason is I just feel the car seems a little less strained when I shift it to N at a complete stop (maybe only me). Of course I dont do it for small signals, but definitely for the longer ones.


Then again for DSG owners, you must shift to N if the duration of the stop is longer than 20 seconds. I remember reading this. DSG is just like an automated manual so when the brake is pressed in D its like pressing the brake and releasing the clutch a bit in a manual.
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Old 13th October 2010, 20:53   #237
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Quote:
Originally Posted by jigbarai View Post
@ samurai / guna -
Btw, i read thru Khangs FAQ. It talks about wear and tear of parts and not Fuel consumption. But it is a good insight into internal operation of slushbox if correctly mentioned. Thanks.
More I think about it, Khanq's theory sounds a tad flawed.

Let us go to a very very basic question here - What is the purpose of the N slot ? If you are supposed to be moving only between P and D - why do manufacturers even bother putting that N slot.
It is there for a reason. And to say that a particular slot causes more wear and tear - does not sound right.

Quote:
Originally Posted by Samurai View Post
How will you start it without moving back to P?
All automatics can be started both in N and P slots. They are designed to do so. They wont start in any other slots.

@blackasta - No issues with this one.

Quote:
Originally Posted by Samurai View Post
The engine is on, so fuel will be spent.
The question is 'how much fuel'.

Quote:
Originally Posted by akshay1234 View Post
Well if it is a longish signal, I do shift the car into N and keep my foot on the brakes. 1 reason is I have to keep the brake pedal pressed less than with the car in D. And the 2nd reason is I just feel the car seems a little less strained when I shift it to N at a complete stop (maybe only me). Of course I dont do it for small signals, but definitely for the longer ones.
Its not just you Akshay - its a common experience. The car is less strained as well as the leg is more relaxed. Not just signals, even in traffic where the stop seems to be beyond 15-20 seconds, I move to N and relax.
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Old 13th October 2010, 21:52   #238
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Quote:
Originally Posted by Samurai View Post
The engine is on, so fuel will be spent.
And slightly more if the engine is loaded more. Will be the first to agree that if the slight diff in FE is that important, what are you doing in an automatic!

Quote:
Originally Posted by Mpower View Post
As far as the brakes, yes wear is nil if there is zero relative motion between pad and rotor but usually there is some motion because most of us are not focused on keeping a firm foot n the pedal and tend to move an inch here and inch there.
Aw. Come on. How much more wear?

Quote:
Originally Posted by jigbarai View Post
More I think about it, Khanq's theory sounds a tad flawed.

Let us go to a very very basic question here - What is the purpose of the N slot ? If you are supposed to be moving only between P and D - why do manufacturers even bother putting that N slot.
It is there for a reason. And to say that a particular slot causes more wear and tear - does not sound right.
I think what he said was more wear because of constantly shifting between D and N/ P.

Just for the record, I apply the handbrake (rather than P) at long stops. Find it easier when moving off. I don't switch off because I like the AC to work all the time.
OT- I'm constantly amazed when I see so called 'luxury' cars driven with the windows rolled down. In the heat.

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Old 13th October 2010, 22:04   #239
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Sorry I should have used the quote indication:

Quote
More often than not one uses the box in the D or N and believe me buddy if you are not paying attention and have shifted to the P on a light, its really very possible that one shifts to R and thinks its a D and goes crashing into the rear. Its happened to all of us

v-16

http://www.team-bhp.com/forum/techni...tomatic-7.html

Can't get more authoritative than that!

I neglected to mention that I myself prefer to keep the engine running, BUT the shift in neutral and my eye on the rear view mirror. I also keep the vehicle positioned so that I can move it past and into an empty space by the front vehicle.

I don't want to sound paranoid and alarmist and cynical, but this is what happened. A friend stopped at an entry ramp and got hit by a truck from behind. This happened in LA, the truck driver was Mexican and without insurance. It was a mess, he had multiple fractures but survived.

Another friend was hit by a truck while waiting at the lights, on a scooter. He lost his life. This was here in Bangalore.

These are the reasons I keep the engine running and the box in neutral. I see a runaway truck in the mirror, I keep the option of getting out of the way open.

The advice I got while in the UK to keep the engine off and the box in gear and the brakes on didn't work too well in the US, when I shifted from P to R and almost creamed the car behind! The driver of that car, a lady, almost had kittens!

The trick about keeping escape routes open in front, I got from the California Highway Manual. Works even when moving.

Became quite well known helping Indian students learn driving: ate more curry in LA in a year than three years in UK courtesy grateful families. In US, without a car, you'll end up with feet like Donald Duck (quote from Cheech Marin, "Born in East LA" HaHa!). Great rescue for me from American food! Hairy experiences of numerous 16 wheeler artics bearing down on me and driving into gang ridden neigbourhoods though.

Just read a few queries:

In P mode the cooling mode (oil circulation pump) is stopped. It may be better to keep the cooling action working.

'Sright that the pawl is locked in P.

Recent Australian Insurance Advisory quotes research showing that 3% fuel savings achieved just shifting to N at lights.

Any more queries, I'll try to answer.

Last edited by proton : 13th October 2010 at 22:23. Reason: Last line added
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Old 13th October 2010, 22:23   #240
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Quote:
Originally Posted by proton View Post
In P mode the cooling mode (oil circulation pump) is stopped. It may be better to keep the cooling action working.
Thats interesting. Hadn't thought of that!
Just realised I don't have a shop manual for any automatic!

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