Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 28th March 2009, 17:20   #106
BHPian
 
Join Date: Jan 2009
Location: Chennai
Posts: 41
Thanked: 15 Times
Default

Quote:
Originally Posted by Motomaniac View Post
I don't think you should do that... O/D is certainly not a fourth gear.. as a matter of fact it acts as one lower gear than you are engaged in... it is to be used for overtaking / getting a surge of acceleration...

For a manual.. it would be that if you are cruising in 5th gear and need to overtake a truck fast, you go to the 4th gear... O/D is for that purpose.

Using it for all times may put pressure on the engine / reduce FE

P.S: the same is as explained in my Corolla a/t manual.
O/D is exactly opposite of what you are saying. O/D will not downshift to the lower gear. In O/D you shift to the higher gear thus helping engine run at a lower RPM and better FE. Technically, O/D means the engine speed is lower than the transmission speed i.e., the gear ratio is less than 1. It will not help you overtake a truck faster, since the torque available will be lesser.

I am posting a link to this article which explains O/D.
What is the transmission’s overdrive? - Ask.cars.com
VeeTee is offline   Reply With Quote
Old 6th October 2010, 21:40   #107
BHPian
 
idofsuresh's Avatar
 
Join Date: Jan 2007
Location: Bangalore
Posts: 156
Thanked: 80 Times
Default

Quote:
Originally Posted by Dippy View Post
Hey dude

You can keep the shifter in D and keep you foot on the brake pedal but that would put pressure on the brakes since in D the car creeps forward. I drive a Zen AT but I always put it in N and pull the handbrake and wait. I prefer that

Yes the tranny does downshift to give you a boost when you press the accel pedal hard. This gives you more punch when you want to overtake

Dippy
+1 to that. I see too many people keep the car on "D" mode when waiting in a traffic light with the brake pedal pressed. I am sure it puts too much pressure on the brakes. No wonder brake disks and pads wear out so fast in automatics. I am sure it wastes fuel too. I am new to driving automatic, but I figured out I should be in "N" and apply hand brake. Needs some getting used to, but trying to make it as a habit.
idofsuresh is offline   Reply With Quote
Old 6th October 2010, 22:17   #108
Senior - BHPian
 
Join Date: Nov 2007
Location: Bangalore
Posts: 2,376
Thanked: 528 Times
Default

Quote:
Originally Posted by idofsuresh View Post
+1 to that. I see too many people keep the car on "D" mode when waiting in a traffic light with the brake pedal pressed. I am sure it puts too much pressure on the brakes. No wonder brake disks and pads wear out so fast in automatics. I am sure it wastes fuel too. I am new to driving automatic, but I figured out I should be in "N" and apply hand brake. Needs some getting used to, but trying to make it as a habit.
Putting the car to N or D (with the brake pressed) doesn't make any difference to the fuel wasted as engine will be just idling at constant rpm. It is only when you take of the feet from the brake the revs rise.
Guna is offline   Reply With Quote
Old 6th October 2010, 22:25   #109
BHPian
 
idofsuresh's Avatar
 
Join Date: Jan 2007
Location: Bangalore
Posts: 156
Thanked: 80 Times
Default

Quote:
Originally Posted by DocG View Post
Shifting from D to P or N at short signals will increase the wear of the gearbox.
Can you please support your claim with a proper reference ? You are making a big statement and if it is true, it is important for people to know and follow.

Quote:
Originally Posted by Guna View Post
Putting the car to N or D (with the brake pressed) doesn't make any difference to the fuel wasted as engine will be just idling at constant rpm. It is only when you take of the feet from the brake the revs rise.
I don't think brake should have anything do to with engine RPM. But with these advanced technologies it is hard to assume anything. I will check on this tomorrow and report. Really simple to check. Keep the car on D+Brake and N and watch the RPM meter.
idofsuresh is offline   Reply With Quote
Old 8th October 2010, 00:41   #110
BHPian
 
idofsuresh's Avatar
 
Join Date: Jan 2007
Location: Bangalore
Posts: 156
Thanked: 80 Times
Default

Guna: Checked it. Putting the car on "N" or "D" without accelerator input is just the same. 750 RPM in my case. Only difference is in the "D" the car moves and in the "N" it stands still. I can't say whether the fuel consumption is same or not in these two cases through. My car does not have an instant fuel efficiency meter. Again, I don't want to assume same RPM means same fuel consumption. If someone with an instant fuel efficiency meter can report (hoping it is accurate), it will be great.
idofsuresh is offline   Reply With Quote
Old 20th October 2010, 15:32   #111
Team-BHP Support
 
noopster's Avatar
 
Join Date: Feb 2010
Location: Pune
Posts: 8,665
Thanked: 9,188 Times
Default

This is an awesome thread!

When test driving the Vento AT recently, a couple of us (independently) experienced a jarring noise when the brake lever is released after putting the car into D. The noise happens at the point of releasing the brake when it is fully depressed If you don't FULLY depress the brake while changing the gear, it doesn't give this noise.

Is this normal? I don't remember this being an issue when I've driven the OHC AT years ago on any of the times I've driven automatics in the US. Stalwarts please advise.
noopster is offline   Reply With Quote
Old 20th October 2010, 17:29   #112
Senior - BHPian
 
Join Date: Nov 2007
Location: Bangalore
Posts: 2,376
Thanked: 528 Times
Default

Quote:
Originally Posted by idofsuresh View Post
Guna: Checked it. Putting the car on "N" or "D" without accelerator input is just the same. 750 RPM in my case. Only difference is in the "D" the car moves and in the "N" it stands still. I can't say whether the fuel consumption is same or not in these two cases through. My car does not have an instant fuel efficiency meter. Again, I don't want to assume same RPM means same fuel consumption. If someone with an instant fuel efficiency meter can report (hoping it is accurate), it will be great.
my car has the instant meter but it remains blank when stationary (since there is no distance covered, KMPL would be zero ). True, same RPM need not mean same fuel burnt as the computer can (if designed to ) feed more fuel to maintain the same RPM.
Guna is offline   Reply With Quote
Old 22nd October 2010, 12:05   #113
BHPian
 
manim's Avatar
 
Join Date: Aug 2008
Location: Tuticorin
Posts: 715
Thanked: 374 Times
Post okay for 'N' at signals

Here are the exact words in my Civic-AT manual:

"Use N if you need to restart a stalled engine, or if it is necessary to stop briefly with the engine idling".

So it is okay if we put in in 'N' for a long wait at signals (with the handbrake on for safety).
manim is offline   Reply With Quote
Old 22nd October 2010, 12:15   #114
BHPian
 
babhishek's Avatar
 
Join Date: Sep 2006
Location: KOLKATA
Posts: 315
Thanked: 14 Times
Default

Quote:
Originally Posted by manim View Post
Here are the exact words in my Civic-AT manual:

"Use N if you need to restart a stalled engine, or if it is necessary to stop briefly with the engine idling".

So it is okay if we put in in 'N' for a long wait at signals (with the handbrake on for safety).
that sums it up perfectly!
N for traffic light situations(long and short) - D and brakes just lead to wear and tear.

In terms of consumption of fuel - there is no difference...
babhishek is offline   Reply With Quote
Old 22nd October 2010, 12:32   #115
BHPian
 
ikoneer's Avatar
 
Join Date: Aug 2007
Location: chennai
Posts: 486
Thanked: 6 Times
Default

While stopping at a signal, its better to put in N + Hand Brake rather than in D + Brake. It will help to avoid sudden moves forward and protect us from road rage.
ikoneer is offline   Reply With Quote
Old 18th April 2011, 18:32   #116
Senior - BHPian
 
Warwithwheels's Avatar
 
Join Date: Aug 2009
Location: India
Posts: 1,251
Thanked: 1,013 Times
Default Re: Suggestions for Team-BHP from Team-BHPians

How about having an Idiot's guide to Automatics? With the number of auto tranny user on the rise everyday, I am sure it would be a big boon, especially to those who are first time drivers. It would be great if the Mods could come up with a detailed write up on the above topic.
Warwithwheels is offline   Reply With Quote
Old 18th April 2011, 19:08   #117
BHPian
 
Xehaust's Avatar
 
Join Date: Jan 2008
Location: Mumbai
Posts: 845
Thanked: 74 Times
Default Re: Suggestions for Team-BHP from Team-BHPians

+1 to that. After we got got an automatic in the house, its been a learning curve on how to use the automatic in the most effecient & correct manner.
i.e. Anyone can drive an automatic, but how to drive it correctly has been a little cumbersome by asking & reading up on it on various sources including the service advisors when the car goes for service.

Generally people think theres nothing to it but dont realise that it could cause harm to the car & that they are getting lower FE due to the incorrect usage rather than because its an automatic.

Case in point: Most people keep the gear in "D" even when halted at traffic lights while just using the brakes. The correct usage is to put it into "N" and let go of the brakes. This incorrect usage results in increased brake wear & higher fuel consumption.

P.S. - A query here is that ive felt that in automatics, the car doesnt decelerate as fast as manuals on letting go of the accelerator. Is this just me or is it technically right?

Last edited by Xehaust : 18th April 2011 at 19:11.
Xehaust is offline   Reply With Quote
Old 18th April 2011, 23:14   #118
BHPian
 
Neilguy's Avatar
 
Join Date: Sep 2010
Location: Hyderabad
Posts: 172
Thanked: 51 Times
Default Re: Suggestions for Team-BHP from Team-BHPians

Quote:
Originally Posted by Xehaust View Post
Case in point: Most people keep the gear in "D" even when halted at traffic lights while just using the brakes. The correct usage is to put it into "N" and let go of the brakes. This incorrect usage results in increased brake wear & higher fuel consumption.
but can you explain why you feel halting at traffic lights with the gear in D would lead to increased brake wear and higher fuel consumption! Putting an AT vehicle in N and letting go of the brakes is the same as putting any geared vehicle in Neutral and not braking. This is DANGEROUS.

And btw, if you want to really "save fuel and reduce brake wear", put the vehicle in P and switch off the engine.

Last edited by Neilguy : 18th April 2011 at 23:22.
Neilguy is offline   Reply With Quote
Old 19th April 2011, 09:29   #119
BHPian
 
Xehaust's Avatar
 
Join Date: Jan 2008
Location: Mumbai
Posts: 845
Thanked: 74 Times
Default Re: Suggestions for Team-BHP from Team-BHPians

Thought this might crop up.

Well, what i meant was that on a level road we should put it into N without the brakes (for a short signal, etc.)
But even on a non-level/incline, it can easily be put into N (keeping the brakes pressed just like you did in D or have the handbrake engaged just like in a MT).

Generally, people just leave it in D & ride the brakes for short stops to avoid the small procedure of moving the gear selector & pressing the brake to do so.
But you should actually select N for short stops while keeping the brake pressed if you are on an incline. If you are stuck in dense traffic or are at a long traffic light on an incline, then you can obviously put it into P.

WHY ITS BAD FOR THE CAR:
The reason for D leading to increased brake wear & higher fuel consumption is that if you notice, when in D, even when the accelerator is not pressed, the car moves forward. This is akin to using just the clutch to move forward in a manual in dense traffic conditions. Now as we all know that this leads to higher fuel consumption but since the brakes are keeping the car in position while the engine is trying to push it forward, this riding of the brakes leads to increased brake wear & heat build up. Another point i forgot is that this also strains the engine.
While keeping it in N with the brakes pressed, the engine is not trying to move the car forward, hence no fuel consumption or break wear or engine strain.

In a nut shell, keeping an AT in D with the brake pressed is like half-clutching while keeping the brake pressed in a MT. Would you ever do that in a MT?

WHY ITS A SAFETY HAZARD TO KEEP IT IN D:
Coming to the safety part, having it in D with the brake is the actual safety hazard as if the brake pedal is left unintentionally, the car will move forward. Hence, actually, this is the DANGEROUS usage rather than putting it into N (on a level road) with the handbrake engaged/P (on a non-level road) wherein the car will not move forward.

@Neilguy - I did not mention this to save fuel & reduce brake wear but rather to use the AT as its supposed to be used. Correct usage doesnt "reduce" fuel consumption or brake wear but actually keeps it at the level it was intended. Not following correct usage is what "increases" the fuel consumption & brake wear above the actual level intended not to mention engine strain. Hence, relative to the wrong usage, the correct usage "reduces" fuel consumption & brake wear while also keeping the engine strain free & healthy when compared to the wrong usage.

P.S. - This is exactly what i meant when i said that most people do not know the correct usage of ATs (including me when i was a newbie to ATs). No offence meant to you Neilguy.

Last edited by Xehaust : 19th April 2011 at 09:59.
Xehaust is offline   Reply With Quote
Old 19th April 2011, 13:52   #120
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,381
Thanked: 14,292 Times
Default Re: Suggestions for Team-BHP from Team-BHPians

Quote:
Originally Posted by Xehaust View Post
@Neilguy - I did not mention this to save fuel & reduce brake wear but rather to use the AT as its supposed to be used. Correct usage doesnt "reduce" fuel consumption or brake wear but actually keeps it at the level it was intended. Not following correct usage is what "increases" the fuel consumption & brake wear above the actual level intended not to mention engine strain. Hence, relative to the wrong usage, the correct usage "reduces" fuel consumption & brake wear while also keeping the engine strain free & healthy when compared to the wrong usage.
Sorry, I do not agree. What you do may improve FE and reduce brake wear. But doesn't mean waiting in D is incorrect. I have been using Auto almost continuous for 18 years, in fact I was properly trained by highly knowledgeable instructors before I got my US license back then. But I didn't hear about this switching to N at signals until few months back, probably in this very same thread.

This waiting in N was probably invented by some FE and brake wear conscious drivers. I have nothing against it, but as far as I know I never seen anybody doing it until I heard it in this thread. I am usually open to new things, so I tried it a few times. Every time I got honked by people behind. With D, I just have to lift my foot. With manual shift, I can shift to 1st gear quickly without looking. But in auto, shifting from N to D has to be done carefully, else it will move further down.

Stopping in N in signals is a habit practiced by some people, it has its merit if you are comfortable with it. But, please do not claim that waiting in D is incorrect. I have never heard it mentioned when I drove in US for a decade, where 99% of the cars are auto. I didn't get a point deduction for not putting it in N in signals during my driver's license road test. I have been to many DL road tests in US for friends and family, never seen anybody lose a point for that. Obviously it is not incorrect.

If FE and wear/tear is the yard stick for deciding right and wrong, then anything other than very sedate driving will be incorrect. All spirited driving will be incorrect since it has adverse effect on FE and brake lining.
Samurai is offline   (2) Thanks Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Driving in India after driving outside (abroad) - tips to avoid common mistakes mmxylorider Street Experiences 24 9th October 2014 20:06
The Driving Tips Thread normally_crazy The Indian Car Scene 43 17th September 2011 21:49
Tips to drive better: But are the tips correct? Spinnerr Technical Stuff 11 22nd June 2009 13:00
Driving Tips.. karthik247 Technical Stuff 3 17th April 2005 16:32
INFO : Tips on driving in Fog Technocrat The Indian Car Scene 2 1st February 2005 10:19


All times are GMT +5.5. The time now is 09:03.

Copyright ©2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks