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


Reply
 
Thread Tools Search this Thread
Old 28th July 2007, 00:31   #16
BHPian
 
thalavoy's Avatar
 
Join Date: Jun 2004
Location: Chennai
Posts: 389
Thanked: 62 Times
Default

As mentioned in the youtube video about heel and toe shifting, 'Brake pads are cheaper than engine parts'. So use the brakes. FE does not make a bigger hole in your wallet
thalavoy is offline   Reply With Quote
Old 28th July 2007, 01:36   #17
Senior - BHPian
 
1100D's Avatar
 
Join Date: Jun 2006
Location: Calcutta
Posts: 4,179
Thanked: 2,358 Times
Default

Quote:
Originally Posted by thalavoy View Post
As mentioned in the youtube video about heel and toe shifting, 'Brake pads are cheaper than engine parts'. So use the brakes. FE does not make a bigger hole in your wallet
Heel toe-ing is not for stopping. It has a different use. Engine braking is not only done to enhance brake life, it is done to aid the stopping process and remain in control.

There are a lot of things said on foreign websites, but they dont have our roads, nor our road conditions and most importantly they dont have our cars and dont drive like us.
1100D is offline   Reply With Quote
Old 28th July 2007, 01:44   #18
BANNED
 
mclaren1885's Avatar
 
Join Date: Jul 2005
Location: Bangalore (the city of modded cars) !!
Posts: 4,821
Thanked: 28 Times
Infractions: 0/1 (10)
Default

thalavoy, heel n toe is used to make sure that one is in the power band soon after shifting and to also make sure that you get the downshift right without having to "wait" for the gear to slot in. Mostly helpful in racing cars and is based on the principle of rev matching.

1100d, I haven't forgotten other parameters like condition of brake pads, tire wear, road surface conditions etc. I was just trying to point out the facts on how to brake keeping out all these parameters just to get a hang on how engine braking works. It goes to say that external parameters as the ones mentioned by you play an equal role as well.
mclaren1885 is offline   Reply With Quote
Old 28th July 2007, 01:53   #19
Senior - BHPian
 
1100D's Avatar
 
Join Date: Jun 2006
Location: Calcutta
Posts: 4,179
Thanked: 2,358 Times
Default

Quote:
Originally Posted by mclaren1885 View Post
1100d, I haven't forgotten other parameters like condition of brake pads, tire wear, road surface conditions etc.
Oh I am quite sure you have not missed those parameters, I mentioned it in the post itself. It was just that I was taking your point further to what you have not said (assuming that people already know).
1100D is offline   Reply With Quote
Old 28th July 2007, 02:48   #20
Senior - BHPian
 
rr_zen's Avatar
 
Join Date: Sep 2006
Location: Chennai, India
Posts: 1,711
Thanked: 262 Times
Default

Quote:
Originally Posted by mclaren1885 View Post
rr_zen, as pointed out by 1100d it is not necessary to shift down in a sequence. By this I mean you don't have to go from 5th - 4th - 3rd - 2nd to stop your car. For eg, say you are at 120kmph in 5th gear. You see something abruptly and decide to stop. What you ought to do is know a few things. Like what speed does your car hit at redline in second gear. What could your rpm's be in case you downshift a couple of gears at one go.

Say if I am doing 180 in a baleno there is no chance of me being able to shift into 2nd from 5th. Since the engine will be over revving and could be fatal to the engine. Instead what I would do is shift into 4th, braking at the same time and shift immediately into 2nd. If I am doing 120 in 5th gear it goes without saying that one can easily shift to 2nd as baleno redlines in 2nd at 100. So if you are judiciously using the brakes and downshifting in this manner it IS the quickest and safest way to stop a car.


Point in case, suppose I am at 120 and need to stop abruptly using the brakes as you pointed out, what could happen is.

1. Locking up of brakes, thus eliminating steering manouvarability and also increasing your braking distance.

2. Transfer of weight from rear end to front end by braking thus the rear end of the car is prone to step out causing massive oversteer which could prove to be fatal once again. Most often the reason why you see cars loosing control on hard braking

To avoid this, were you to use engine braking the weight transfer will move towards the rear keeping the car in a more stable condition, prevent tire locking and enable you to maybe steer away from danger. Also the fact that now that you are in the right gear you could use the power on tap and accelerate away from the obstacle. By staying in 5th gear to duck either sides of the obstacle will be impossible.

As 1100d has pointed out its an instantaneous reaction once you understand how it works.

On seeing the obstacle, brake lightly with right foot. Go on the clutch with your left foot, use left hand to downshift into a suitable gear while maintaining steering position with the right hand. Continue to brake with your right foot GRADUALLY and not abruptly how ever panic stricken the situation maybe. Keep calm and remember the basics. Half the accidents in India are caused due to people not following this simple technique.
Thanks for your time and effort in explaining to the minutest detail. Please note that I am not trying to disagree with what you said. If you go through my earlier post yet again, I fully appreciate that engine braking is the best way to reduce speed in a safe manner. However, as I said earlier, the amount of time in hand is the deciding factor here. And your point on keeping calm and remembering basics during such a situation is pertinent too, but tell me honestly how many can do it or consciously do it. It is not a simple rule(like wearing seat belts)that can be followed easily but something that requires one to have real guts and not to panic. Preaching this is easy but putting it to practice may be difficult and may take time. And, how many times do we frequently get into such a situation is also something that we would need to think about, for us to practice ourselves.
rr_zen is offline   Reply With Quote
Old 28th July 2007, 03:00   #21
BANNED
 
mclaren1885's Avatar
 
Join Date: Jul 2005
Location: Bangalore (the city of modded cars) !!
Posts: 4,821
Thanked: 28 Times
Infractions: 0/1 (10)
Default

Quote:
Originally Posted by rr_zen
However, as I said earlier, the amount of time in hand is the deciding factor here.
It doesn't take much time actually. If you know what to do. And I am saying this from experience. Atleast you will not have to pray to god this way . You will still be in control (atleast better than sitting on the brakes and praying).

Quote:
Preaching this is easy but putting it to practice may be difficult and may take time.
So its time to put age old practices to the dustbin and learn new, safer techniques. Remember whats important is your safety, so I guess we should take that extra care to do whatever is necessary like wearing helmets or seatbelts. Its not as tough as its made out to be here. I am talking from personal experience. And you don't have to be in tight situations to learn this technique. You can learn it on an empty road too each time trying to better the braking.
mclaren1885 is offline   Reply With Quote
Old 28th July 2007, 13:27   #22
Senior - BHPian
 
Surprise's Avatar
 
Join Date: Feb 2005
Location: Chennai
Posts: 2,299
Thanked: 129 Times
Default

Quote:
Originally Posted by mclaren1885;514397
Say if I am doing 180 in a baleno there is no chance of me being able to shift into 2nd from 5th. Since the engine will be over revving and could be fatal to the engine. [B
Instead what I would do is shift into 4th[/b], braking at the same time and shift immediately into 2nd. If I am doing 120 in 5th gear it goes without saying that one can easily shift to 2nd as baleno redlines in 2nd at 100.
I have a question, mclaren

When we want to shift into lower gears for engine braking, obviously we need to press the clutch. Will this not result in increased stopping distance? (takes out the efficiency of braking distance)
Surprise is online now   Reply With Quote
Old 28th July 2007, 15:34   #23
BANNED
 
mclaren1885's Avatar
 
Join Date: Jul 2005
Location: Bangalore (the city of modded cars) !!
Posts: 4,821
Thanked: 28 Times
Infractions: 0/1 (10)
Default

Quote:
Originally Posted by Surprise View Post
I have a question, mclaren

When we want to shift into lower gears for engine braking, obviously we need to press the clutch. Will this not result in increased stopping distance? (takes out the efficiency of braking distance)
Yes, but the shifting has to be done quickly. You are hardly on the clutch for 1-2 secs, sometimes less. But once you let go of the clutch the car will slow down much faster. Infact the very act of releasing the clutch after shifting you will notice the difference in the speeds. Its hard to explain, but once you do this it will be much easier to understand.

Find an empty road, open 3rd gear. Then brake little, shift into 2nd asap. With steady braking. You will notice the difference. Then do about the same speed and try only braking. This way you will know which is better.
mclaren1885 is offline   Reply With Quote
Old 28th July 2007, 16:42   #24
Distinguished - BHPian
 
BlackPearl's Avatar
 
Join Date: Aug 2005
Location: Calcutta
Posts: 2,311
Thanked: 4,368 Times
Default

Quote:
Originally Posted by mclaren1885 View Post
Yes, but the shifting has to be done quickly. You are hardly on the clutch for 1-2 secs, sometimes less. But once you let go of the clutch the car will slow down much faster. Infact the very act of releasing the clutch after shifting you will notice the difference in the speeds. Its hard to explain, but once you do this it will be much easier to understand.

Find an empty road, open 3rd gear. Then brake little, shift into 2nd asap. With steady braking. You will notice the difference. Then do about the same speed and try only braking. This way you will know which is better.
@mclaren.. IMO what you are suggesting will cause the car to buck and put tremendous strain on the drivetrain, gearbox and engine mountings... so IMO heel toe is a must to avoid stress on these things... and IMO engine braking is not only the braking due to downshifts, its the braking caused as soon as one lifts of the accelerator, presses the brake pedal wihtout pressing the clutch... please correct me if I am wrong...
BlackPearl is online now   Reply With Quote
Old 28th July 2007, 19:19   #25
BANNED
 
mclaren1885's Avatar
 
Join Date: Jul 2005
Location: Bangalore (the city of modded cars) !!
Posts: 4,821
Thanked: 28 Times
Infractions: 0/1 (10)
Default

Quote:
Originally Posted by BlackPearl View Post
@mclaren.. IMO what you are suggesting will cause the car to buck and put tremendous strain on the drivetrain, gearbox and engine mountings... so IMO heel toe is a must to avoid stress on these things...
BlackPearl, I cannot validate the amount of stress it would put on the gearbox & engine mounts but I am told that this practice is good for running in of engines too and is used to exhibit gradual deceleration.

Quote:
and IMO engine braking is not only the braking due to downshifts, its the braking caused as soon as one lifts of the accelerator, presses the brake pedal wihtout pressing the clutch... please correct me if I am wrong...
I didn't quite get what you are trying to say here. Engine braking is slowing down of the car once you shift to a lower gear along with braking. I don't know what you mean by "without pressing the clutch". Engine braking cannot be done as such.
mclaren1885 is offline   Reply With Quote
Old 28th July 2007, 19:51   #26
BHPian
 
Join Date: Oct 2005
Location: chennai
Posts: 757
Thanked: 299 Times
Default

Quote:
Originally Posted by mclaren1885 View Post
It doesn't take much time actually. If you know what to do. And I am saying this from experience. Atleast you will not have to pray to god this way . You will still be in control (atleast better than sitting on the brakes and praying).
rr,

I agree with rahul, it is not that difficult as you think. it requires quite a bit of practice. Perhaps as mcl mentioned, one needs to try practicing the technique in an empty road or even during normal driving provided no one is behind you.

you should comfortable with this technique to a level where the motor system of the body takes over the control in such situations. one should be unconsciously competent with the technique.
tifosikrishna is offline   Reply With Quote
Old 28th July 2007, 22:51   #27
Distinguished - BHPian
 
BlackPearl's Avatar
 
Join Date: Aug 2005
Location: Calcutta
Posts: 2,311
Thanked: 4,368 Times
Default

Quote:
Originally Posted by mclaren1885 View Post
I didn't quite get what you are trying to say here. Engine braking is slowing down of the car once you shift to a lower gear along with braking. I don't know what you mean by "without pressing the clutch". Engine braking cannot be done as such.
AFAIK one does not have to shift to lower gear for engine braking.. engine braking starts as soon as one lifts of the accelerator... what I meant is that as long as someody does nor presses the clutch and brakes simultaneously during slowing the car down one will use engine braking... obviously if one shift down he engine braking will be more pronounced...
BlackPearl is online now   Reply With Quote
Old 28th July 2007, 23:17   #28
Senior - BHPian
 
Surprise's Avatar
 
Join Date: Feb 2005
Location: Chennai
Posts: 2,299
Thanked: 129 Times
Default

Quote:
Originally Posted by mclaren1885 View Post
Yes, but the shifting has to be done quickly. You are hardly on the clutch for 1-2 secs, sometimes less. But once you let go of the clutch the car will slow down much faster. Infact the very act of releasing the clutch after shifting you will notice the difference in the speeds. Its hard to explain, but once you do this it will be much easier to understand.
I am trying this for quiet sometime & could understand that even with slight help of brake pedal the car could be stopped with engine braking playing a major role.

But Iam very much hesitant to try this out during emergency situations.

Not a welcome move, if we miss the sweet spot handling in engine braking (i.e the noise d the way passenger feels the shake)
Surprise is online now   Reply With Quote
Old 29th July 2007, 00:31   #29
BHPian
 
thalavoy's Avatar
 
Join Date: Jun 2004
Location: Chennai
Posts: 389
Thanked: 62 Times
Default

@mclaren; @1100d - probably I didnt explain it fully. In that video, the driver was commenting. There was once he was about to take a U turn or something and he was using brakes to stop and not changing gears (engine braking). At that time he was commenting that brake pads are cheaper to replace. So, if you need to stop fast, use your brakes, rather than down shifting gears.
This applies to our driving too, not just foreign or racing styles.
thalavoy is offline   Reply With Quote
Old 29th July 2007, 01:33   #30
Senior - BHPian
 
razor4077's Avatar
 
Join Date: Sep 2006
Location: Mumbai
Posts: 1,875
Thanked: 252 Times
Default

Nice discussion. My 2 cents...
Engine braking is something that becomes an instinct, a habit, after one uses it regularly. The gut reaction that most of us have is to stand on the brakes in case of a sudden obstacle. But someone who is used to engine braking, i.e, rapid downshifting, combines both in such a situation. I personally use a combination of brakes and downshifting to slow down. It's become a habit now... hardly think twice about it.

Heel'n toe, something that Blackpearl introduced me to, is a great way to carry speed into the lower gears without straining your engine and tranny, but it is not a technique to help you slow down.

I have a point I would like some opinions on. Is downshifting a good way to slow down on a wet patch of road? I have heard that the sudden change in velocity can cause the tyres to skid. Is this true? I have used it with no ill effects (much safer than using the brakes IMHO and experience).
What is the way you recommend to slow down on a wet road (which may have standing water)?
razor4077 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
GreenLight: Reduce traffic jams by eliminating 'right turns' at signals D4D Street Experiences 47 6th November 2014 09:40
Can speed cameras reduce road mishaps? ad3952n Street Experiences 22 8th September 2014 14:23
How effective is the auto-cut mechanism of the fuel service stations? Zappo Technical Stuff 35 27th March 2009 14:34
USA - Proposal to reduce Speed limit to 55 mph appuchan The International Automotive Scene 37 1st August 2008 23:30
Hydraulic Bonnet Opening Mechanism.How do i install nikibusa Modifications & Accessories 7 26th April 2007 13:40


All times are GMT +5.5. The time now is 21:47.

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