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Old 12th January 2009, 19:04   #121
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Originally Posted by m_upreti View Post
Got the point, what I meant was what does one do in case of engine failure / no fuel while going downhill.

The hand brakes will not hold....
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.
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Old 12th January 2009, 19:10   #122
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Engine braking will work even when an engine is off.
Care to explain how?
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Old 12th January 2009, 19:24   #123
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Hi Anup,

I was in a Wagon R 2003 Lx model.

I literally stood on the brakes, they were just jammed in the upright position.

The car was in neutral & engine was off.

The brakes came in the moment the engine was started.

I promised myself never to do such an experiment again.

Quote:
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.
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Old 12th January 2009, 20:49   #124
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Originally Posted by Technocrat View Post
Care to explain how?
Engine braking is dependent on compression. Regardless of whether the engine is on or off, compression WILL occur. Do try it in your car.

Brakes are power ASSISTED. There is no reason for them to completely fail if the engine is off. Please try again at some safe venue.
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Old 12th January 2009, 21:05   #125
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But how would you do engine breaking if the engine is off?

Yes with engine off the power assisted brakes would still work but in a fashion which would need sue of force
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Old 12th January 2009, 21:51   #126
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I'll post what I know of.

My habit (be it cars or bikes ) is to use the clutch at the last moment when the engine JUST gets on the verge of stalling. Use engine braking to assist me since I dont want to rely completely on brakes thanks to an indicent which I had experienced with the Premier Padmini my dad had in last decade.

Now on shifting to Neutral or Pressing Clutch while braking, only advantage I see in it is the car(or be it a bike) doesnt overrev. Pressing the clutch would be the worst option since it'd needlessly wear the clutch more. Shifting to neutral would have its disadvantage since you'd need to slot it into a gear first if you by chance suddenly needed to accelerate.

Okay now on WHY engine braking is safer.

in cities we'd normally not realise this, but brakes do heat up a lot and they can fail if extensively heated up. In most of the indian cars , the discs are solid and do not have any holes for aided cooling, most only have [||||||] grooves made along the circumference of the disc to aid in cooling by creating turbulence.

the brakes in the premier padmini failed when my parents and me were coming downhill from Mt abu in 1992 ( i do not remember the incident, as told by dad) the brakes failed due to the hydraulic pipe's leak cause the pipe material had got brittle and while coming down the brakes failed all of a sudden. fortunately dad wasnt doing more than 40-50kmph and he slotted the gear into 2nd and then the 1st and stopped finally by dashing the car to the mountain side of the road at 10kmph with a thud.

Now if engine braking hadn't been applied ... God knows what might have had happened.

Now engine braking also has to be done with some knowledge. if you downshift 2-3 gears you're bound to lock your wheels since the gearbox shaft's rpm would be much lower than the wheel's speed so the shaft would abruptly try to slow the wheel down resulting in a lock (irrespective whether you have an ABS or EBD) and since I know that most of the cars in India dont have slipper clutches.

i hope this is not OT
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Old 12th January 2009, 22:32   #127
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Quote:
Originally Posted by m_upreti View Post
I experimented this once in my Wagon R on a straight empty downhill road, I could see up to a Km at least, in neutral with engine switched off . To my horror I realised that I had no brakes, the pedel after a couple of pumps was jammed. Brakes came on the moment I switched on the ignition.

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.
I second that. I have tried to leverage the momentum during downhill drives several times by shifting to neutral (but engine is on idling) and cruising with brakes. It works. However, once i went a step further by turning off the ignition after shifting to neutral. But the brakes wouldn't just work and they became much much harder. Guess the electrical power to the brakes was cut off. Horrified, I turned on the engine hurriedly and the brakes were back to working normally again. This is on my OHC generation 2.
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Old 12th January 2009, 22:52   #128
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Safety is much important that few milli fuel. So in my opinion its better to be in gear all through when your vehicle is moving. When it comes to a stand still apply park break and shift to neutral. This is what I do.(City or Highway)
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Old 12th January 2009, 22:55   #129
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Originally Posted by HotChillyPepper View Post
Safety is much important that few milli fuel. So in my opinion its better to be in gear all through when your vehicle is moving. When it comes to a stand still apply park break and shift to neutral. This is what I do.(City or Highway)
I follow the same practice ! although once something was on my head and i started off with the parking brakes (ashamed)
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Old 12th January 2009, 22:57   #130
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With the engine off, the car will drive the engine rather than the engine driving the car. If the ignition is turned on, the engine will start --- as we all know from push-starting a car with a flat battery. We also know, from that experience, exactly what engine braking feels like, as the guy in the car releases the clutch. Of course, this is in low gear, so magnified.

Yes, I agree, engine breaking will still be there with the engine turned off, because compression will still be there.

I don't think it would do the engine much good, but if I found myself out of control on a hill, that would be the last of my worries!

HotChillyPepper, I agree; coasting, anywhere, is bad driving practice and should be avoided. It is not worth that small amount of fuel

Last edited by Thad E Ginathom : 12th January 2009 at 22:59.
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Old 12th January 2009, 23:31   #131
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hey are we talking about engine braking in the sense of emergency braking or in its pure form in which case only a running engine qualifies.
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Old 12th January 2009, 23:43   #132
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Quote:
Originally Posted by Technocrat View Post
hey are we talking about engine braking in the sense of emergency braking or in its pure form in which case only a running engine qualifies.
we don't forsee emergencies do we ? what we gain as experience while driving/riding we apply it instantly in an emergency. so its better to gain experience on safer side right ? even though it'd be expensive for some more fuel wasted ?
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Old 13th January 2009, 11:39   #133
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Hi Anup,

I don't think will be doing that experiment again with the Truck I own now.

The Wagon R I experimented was with me for over 5 yrs when I undertook that "experiment" & I knew its behaviour in most of the circumstances except this, so I was in better control.

I am still in the process of learning to handle the Scorpio.

Quote:
Originally Posted by anupmathur View Post
Engine braking is dependent on compression. Regardless of whether the engine is on or off, compression WILL occur. Do try it in your car.

Brakes are power ASSISTED. There is no reason for them to completely fail if the engine is off. Please try again at some safe venue.
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Old 13th January 2009, 13:49   #134
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Originally Posted by Technocrat View Post
hey are we talking about engine braking in the sense of emergency braking or in its pure form in which case only a running engine qualifies.
Can you describe the difference?
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Old 13th January 2009, 15:25   #135
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Why would some one have engine not running & try to stop the car by using engine braking under normal circumstances?

What I mean in pure form is, that when we talk about engine braking we talk about instances when the engine is running.

I hope its clear now
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