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Old 14th January 2009, 01:35   #151
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Quote:
Originally Posted by m_upreti View Post
...I need to understand are the brakes getting power from the engine, in that case what happens if the engine fails & u need to stop.
Quote:
Originally Posted by Gasoline View Post
Please remember, if the car equipped with power brake,power steering then it operates with a hydraulic pump...
Small correction - even though the braking system is hydraulic, the brake booster actually works on vaccuum created in the manifold.
(Also, i may as well mention that not all power steering systems are hydraulic)

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Originally Posted by appuchan View Post
Engine braking helps when you have to stop soon, like in a traffic signal or jam, but if your intention is to save fuel and muster maximum momentum, clutch or neutral is the best option. This is with respect to hyper-miling that is...
Appuchan, you clearly havent read this thread in entirety.

Please re-read this post : http://www.team-bhp.com/forum/226145-post32.html
And heres one more from a few weeks back saying the same thing : http://www.team-bhp.com/forum/1107950-post103.html

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Originally Posted by anupmathur View Post
Engine braking will work even when an engine is off.
Problem lies with the steering and the brake system. Both will require a MUCH larger effort to operate. Please note that the brakes do not fail, they just become very much more difficult to apply, with no vacuum/power assist.
Absolutely correct.

Im not sure why m_upreti says his brakes didnt work at all, i think the large difference from booster/power brakes to non-power brakes provides such a contrast that he was under the impression that they werent working at all.
The pedal gets hard, and it takes a lot more force to operate the brakes.
(Also, whether they work as well as OEM non-assisted brakes is questionable... probably not).

Previous discussion here : http://www.team-bhp.com/forum/techni...-goes-off.html (Brakes fail when engine goes off)

Quote:
Originally Posted by im_srini View Post
Hi guys, a n00b question here... Is it frictional losses or compression that helps during engine braking ? While you're expending energy in trying to compress air during the compression stroke, won't it be returned once the piston is past TDC since the compressed air would just act as a spring ? ...
Glad you brought that up srini.
In short, yes, there is a spring effect, and that is why for REAL engine braking you have contraptions like the jake-brake. (It basically opens the exhaust valves at the TDC of the compression stroke, causing a vaccum on the "power" stroke, hence retardation both ways!)
See: http://www.team-bhp.com/forum/techni...rakes-why.html (Signs saying "No engine brakes" - Why?)

We have discussed this "air spring" in this thread : http://www.team-bhp.com/forum/techni...tml#post901577 (What is right mechanism to reduce speed?)
(Post 75 onwards)

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Originally Posted by anupmathur View Post
Hey, if that is how things happened, you've got yourself the ever-elusive Perpetual Motion Machine! .....
Not really anup, once the "air spring" is expanded, it takes external force to squish it. Back to the drawing board for that perpetual motion machine!! (http://in.you tube.com/watch?v=hl8dM2wQB4k&feature=related)

cya
R

Last edited by Rehaan : 14th January 2009 at 01:40.
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Old 14th January 2009, 02:07   #152
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Oh yes... see what you mean

But if I was coasting down a hill with the engine off (which I wouldn't be), and suddenly felt the breaks not work, assuming I had the presence of mind, I'd put the car in gear.
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Old 14th January 2009, 09:28   #153
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Originally Posted by Thad E Ginathom View Post
Oh yes... see what you mean

But if I was coasting down a hill with the engine off (which I wouldn't be), and suddenly felt the breaks not work, assuming I had the presence of mind, I'd put the car in gear.
Thad, it is inconceivable that you'd ever be coasting downhill with the engine turned off!

What is not inconceivable is that the engine might die on you, for reasons best known only to the errant engine! That's when we need to remember the braking power that even the 'dead' engine can provide!

And, if all goes well, nothing will be breaking during such braking, LOL!
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Old 14th January 2009, 12:58   #154
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Hi,

After this incident I did another experiment with the car safely parked in my premises, with the engine switched off & gears in neutral, I braked initially I could pump the brakes, they gradually got harder and after a point the same issue which I faced downhill, the brakes would not budge.

I am not a big guy (only tall), so to see if strength was the matter I called one of my friends who is a amature body builder & spends at least 3 hrs in the gym daily to try push the pedal, he also tried but to no avail, the pedle was just jammed in the top most position.

Then I started the engine & magic, brakes working as normal.

The brakes in the car were OEM, the car had run only 15000 kms, and was being serviced at A.S.S. at the required intervals, where I made sure that the brakes wre being adjusted properly.


Quote:
Originally Posted by Rehaan View Post
Im not sure why m_upreti says his brakes didnt work at all, i think the large difference from booster/power brakes to non-power brakes provides such a contrast that he was under the impression that they werent working at all.
The pedal gets hard, and it takes a lot more force to operate the brakes.
(Also, whether they work as well as OEM non-assisted brakes is questionable... probably not).R
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Old 14th January 2009, 13:44   #155
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Originally Posted by m_upreti View Post
Hi,

After this incident I did another experiment with the car safely parked in my premises, with the engine switched off & gears in neutral, I braked initially I could pump the brakes, they gradually got harder and after a point the same issue which I faced downhill, the brakes would not budge.

I am not a big guy (only tall), so to see if strength was the matter I called one of my friends who is a amature body builder & spends at least 3 hrs in the gym daily to try push the pedal, he also tried but to no avail, the pedle was just jammed in the top most position.

Then I started the engine & magic, brakes working as normal.

The brakes in the car were OEM, the car had run only 15000 kms, and was being serviced at A.S.S. at the required intervals, where I made sure that the brakes wre being adjusted properly.


but that's is a sign to be cautioned ! brakes are supposed to be independent of power assistance (powerassist is just to make it more effective and easier for the driver that's it).

Agree the feather touch feel wouldn't be there. but it should work !

(side Q - does Indica have power assisted brakes ?)
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Old 14th January 2009, 18:24   #156
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Hi Xeno,

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Originally Posted by Xeno View Post
(side Q - does Indica have power assisted brakes ?)
Yes. All indicas and cousins do come with them.
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Old 16th January 2009, 13:01   #157
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That's what I had thought before I ventured in the scary experiment.

Let me try the same thing with my Scorpio (safely parked in my building, with ignition off) and update on the results.

Quote:
Originally Posted by Xeno View Post
but that's is a sign to be cautioned ! brakes are supposed to be independent of power assistance (powerassist is just to make it more effective and easier for the driver that's it).
Agree the feather touch feel wouldn't be there. but it should work !
(side Q - does Indica have power assisted brakes ?)
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Old 20th January 2009, 13:23   #158
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Originally Posted by netarchie View Post
100 km/hr and when i see the sign - Toll 1000 meters ahead - i simply shift to the neutral and break gently till I approach the Toll booth
You could loose control of the car in neutral at such a high speed!

Quote:
Originally Posted by wolfinstein View Post
I don't see anything wrong, if you are at some distance and see the red light is RED..then yes shift to Neutral if you want...! Otherwise practically shift to a lower gear than the one you are in and slow down...! and when you come to a stop Go Neutral...!
Unless one is doing less than 30 kph, it is not advisable!

Quote:
Originally Posted by karthik247 View Post
Never shift from 80kmph to neutral suddenly as it can disturb the balance of the car.
Sir, how does it affect the balance of the car?

Quote:
Originally Posted by Steeroid View Post
If you're first in the row, you should also shift to 1st and keep the clutch disengaged with one hand on the handbrake so that you can release the handbrake, release the clutch and move without holding up traffic behind you.
Sir, keeping the clutch pedal pressed while in gear and stationary at traffic light is detrimental to the vehicle.


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Originally Posted by netarchie View Post
... now the hard part will be to kick the habbit.
Thats very easy when you understand and appreciate the aftermath of some crazy accidents and how and why they happened!
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Old 20th January 2009, 14:21   #159
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Originally Posted by headers View Post
You could loose control of the car in neutral at such a high speed!
Umm no, that makes no sense. Why would you lose control?

Quote:
Originally Posted by headers View Post
Sir, keeping the clutch pedal pressed while in gear and stationary at traffic light is detrimental to the vehicle.
You can hold the clutch down with your car in gear indefinitely with NO wear. Only partial "clutch riding" leads to wear.

Guys - there is a LOT of good info in this thread - particularly posts 55 through page 8. However there is also a ton of nonsense.

Here are a few points:

*Braking is your BRAKE's sole purpose and duty. Your transmission is a transmission, NOT a brake. If your brakes are so bad that you need to use the transmission to brake - get a better car.

* Simply coasting in neutral when driving straigh ahead is NOT bad. You wont magically lose control. I can't forsee any reason to do this though.

* When engine braking - be careful! In a RWD car the engine's negative power load can lead to lift-off oversteer. Typically this is an issue only on large displacement sports cars with high inertia.

* In India it seems to make sense to be in gear all the time because you
never know what's going to happen.

* Never change gears while braking AND cornering. With so many things happening you stand a good chance of losing control. Always go into gear and de-clutch BEFORE you enter a corner.

* Always keep an eye on your rear view mirror to confirm that the person behind you isnt going to hit you if you start braking. Do this well before you brake and do this often! I have avoided at least 1 accident by watching for careless drivers this way (distractions like food, cell phone, news paper, changing diapers etc )

*ALWAYS be aware of who is around you and constantly plan "escape strategies" when driving. This is a great way to be accident free, because you have your exit routes planned just in case. Of course this means that you should never be "boxed in" where you cant get out.

I think thats about it for now...flame suit on!
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Old 20th January 2009, 14:23   #160
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During my recent highway trip, I attempted to overtake a van, with no oncoming vehicle, on an undivided road at around 100 kmph. The van driver never budged to my indications to overtake and kept accelerating. Since there were no vehicles at opposite direction, I kept moving forward until there was a bumpy road surface on the right hand side of the road.

I realized that my left foot pressed the clutch when the car was riding through the bumpy surface. I could recollect on a similar situation too (5-6 months back), I did the same thing.

Any harm in doing that?

If yes, I need to kick out that habit

PS: I rarely do that, may be once in a year
ps-1: Might be when the situation gets risky
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Old 20th January 2009, 14:27   #161
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Quote:
Originally Posted by headers View Post
Sir, keeping the clutch pedal pressed while in gear and stationary at traffic light is detrimental to the vehicle.
I think it should not harm the vehicle as you said. I have many people follow this. Other please shed more light on this practice
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Old 20th January 2009, 15:59   #162
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Quote:
Originally Posted by Surprise View Post
I kept moving forward until there was a bumpy road surface on the right hand side of the road.

I realized that my left foot pressed the clutch when the car was riding through the bumpy surface. I could recollect on a similar situation too (5-6 months back), I did the same thing.

Any harm in doing that?
Why would you clutch just because you were driving over bumps?
If you are accelerating and partial-clutching, I can see it wearing on your clutch a bit. I don't think you did anything "wrong". Can someone clarify?
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Old 20th January 2009, 16:59   #163
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Quote:
Originally Posted by Surprise View Post
I realized that my left foot pressed the clutch when the car was riding through the bumpy surface. I could recollect on a similar situation too (5-6 months back), I did the same thing.

Any harm in doing that?

If yes, I need to kick out that habit
Surprise, you need to kick that habit. It's like coasting in neutral. You have far less control while in this mode.
And you certainly not be half-clutching!
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Old 20th January 2009, 17:58   #164
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Quote:
Originally Posted by Atlblkz06 View Post
Umm no, that makes no sense. Why would you lose control?


You can hold the clutch down with your car in gear indefinitely with NO wear. Only partial "clutch riding" leads to wear.
Well, welcome to Tbhp! The chances of losing control at higher speeds without any "engine drive" is definitely way higher than the other way around!

With regard to the clutch wear - atleast the old school recommends one not to keep the clutch depressed and gear engaged while stationery at traffic lights et all.
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Old 20th January 2009, 19:45   #165
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Quote:
Originally Posted by headers View Post
Well, welcome to Tbhp! The chances of losing control at higher speeds without any "engine drive" is definitely way higher than the other way around!
Vikram, how one will lose control by depressing hte clutch at higher speeds. I knew thats not advisable and that the precise reason why I had raised here, but wanted to know the real impact so that I get out of that quickly
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