Deceleration using gears down a slope - Fuel Consumption?

[Horse_rider]

i think
high RPM=more fuel consumption=more engine and gear wear=more cost to engine and gear

and

Low RPM=less fuel consumption=less engine and gear wear=more brake wear=dangerous if brake fails=no safety=more cost to brake pads

therefore i am using both i.e i put the car in low gear and if the Rpm goes up i use brakes to normalize RPM.

I am from Malakand, and whenever i come to Islamabad i travel 20 KMs downhill continuously, so if i use only brakes with 3rd or 4th gear then my brakes start giving screeching noise, and it become slightly unresponsive. but if i use 2nd gear with brakes and let the brakes cool for sometime whenever the RPM is low, then this problem don't occur but one disadvantage is that, i travel the 20KMs in more time because of 2nd gear. that's good for me.

about fuel consumption, i think safety comes first so the cost benefit is in long run.

[wittycranium]

I personally do not like engine breaking, your gearbox and engine are more precious then discs/pads.

In Emergency, this is a good idea.

Yes engine and gears are more precious, but you will not harm them as along as you are keeping below the red line and you are doing it smoothly, not jerking the system too hard. In local cars i'd suggest at least 1,500 RPm below the redline would be ok.

It would consume slightly more fuel as engine will rev more

i think
high RPM=more fuel consumption

Completely wrong assumption. The revving of engine without pressing the accelerator pedal does not equal more fuel consumption.

Actually, it might be even less than idling.

You see, when you are accelerating at a high RPM, the power of the engine is being delivered to the wheels through the clutch and transmission, the power of the engine comes when you burn fuel, hence more fuel consumption.

On the contrary, when you are going down hill, while the clutch is engaged (pedal not pressed, car in gear, not neutral), it is not the burning of fuel that is revving the engine, it is the force of gravity and your forward momentum that is moving your wheels which are connected to your crank shaft through the clutch and transmission. So here the gravity and forward momentum is causing high RPM, not fuel.

This is why we have better fuel consumption while going downhill and on the highways, even with high RPMs.

Correct me if I am wrong.

[cracked]

lucky bilal,brother wen u NEUTRAL the button on cng switch,cng and petrol will be cut n car is prone to shut off...how on earth u came up with idea lyk tht?

[onlyfaith]

while descending fuel consumption is less even at high rpm specially in current engine technology,(dont want to go in details), neither too high rpm nor continuous braking is recommended as in both cases either engine,gear box,clutch plate(in case of low gear) or brake discs and pads(continuous braking) would be ruined.
i would recommend a general rule

"DESCEND IN THE GEAR IN WHICH UR VEHICLE CAN EASILY ASCEND THE SAME SLOPE" and use brakes when required.
please correct me if im wrong

+1

[doubletrouble]

I think and what i have read the recommended method of controlling speed downhill is by using the braking power of engine and not brakes(it doesn't harm ur engine,gear box) as the brakes may overheat which can result in break failure and very dangerous consequences. So it is not a matter of disc cost but the car and occupants themselves are at risk.Below can be dangerous outcomes of using your brakes:
Hazardous Outcome #1:
You could significantly wear our your brakes.
We're talking... you could actually reduce the life of your brakes by months or even years, depending on the degree to which you "ride the brake" on such steep grades.

Hazardous Outcome #2:
You could lose your brakes altogether! No joke.
That stench of brake dust (that goes hand-in-hand with squealing brakes) is a sign that your brakes are too hot. If you overheat your brakes and don't take enough time in between to let them cool off a bit, then you can actually fry your brakes -- leaving you with virtually NO stopping power at the bottom of the hill.
You may even begin to see SMOKE coming from your overheated brakes. Everyone knows, where there's smoke there's fire, so you're really taking your chances at this point.
Check out these links:

How to Drive Downhill With a Manual Transmission | eHow.com

How To Drive Down Steep Hills... Without Using Your Brakes! - The Fun Times Guide

+1
outcome 2 ....have experienced thrice, 2 times on my way back from Monal, and once on my way back from murree ..extreme fading, had to stop the car for a while to let them cool off instead of totally failing which happened once while coming back from monal

downshifting without jerking off ur whole car is perfectly okay while applying minimal brakes ..so engine and brake pads both will stop ur car without takin much burden

if you have those plastic thingy on ur wheels...take it off, brake cooling would be comparatively better and thus the braking ..experimented in all weathers and in all conditions:)

[xain91]

Sir your car has a rev limiter but do not try this on local cars like XLi/ GLi etc.

I personally do not like engine breaking, your gearbox and engine are more precious then discs/pads.

In Emergency, this is a good idea.

It would consume slightly more fuel as engine will rev more

man its nothing about what you like! you simply got no option other than engine braking if the distance is long. braking continuously increases the temperature of brake pads to such a level that they expand, causing brakes to be least effective and obviously a terrible crash!
so im my opinion you simply cant perform CBA when your life is at stake! simple as that.

[xain91]

Another point is that if you car has alloy rims(less spokes), they allow maximum ventilation of discs so the brake effectiveness is increased by a large percentage as compared to simple steel rims.

[qwertypoiu]

This is not relevant to topic but ever tried going down in neutral its extremely fun

[autophile]

Many a time while coming down form Pir Sohawa, I have stopped in the way to check my wheels for the stench, but thanks God it was not from my car, but other motorists. Many motorists do not know how to drive down hill. Every car manual mentions how to do it. As somebody said above, climb down the hill in same gear in which you climbed up using the breaks to control the speed. Safety first, CBA later.

[autophile]

This is not relevant to topic but ever tried going down in neutral its extremely fun

Use to do it on my 80cc bike and then Datsun 120Y. I now feel it was stupid to do that, but did it as a habit without losing breaks, traction. Old cars were so fun. Today's cars are just toys.

[margallar]

expert drivers use this techniqe when breaks are dead. i was told this when i wal learning to drive

[margallar]

the most advisable thing is to never go above 50 and keep it at second gear it will give good climbing performance and will keep speed low when going downhill

[luckybilal]

@Lonely_Puma: If your car don't have CNG, I am afraid you can't drive with my technique. Yes one should be on petrol first before going to neutral. Car on CNG -> Shift it to Petrol -> Immediately Shift it to Neutral...You are done!

@autophile: Yes the engine will be runing. It is not possible with 'engine shut' as you mentioned. I wrote DON'T SWITCH OFF YOUR ENGINE. So the engine is not switched off.

@2c: It will not even consume water in the radiator. Offcourse it is great technique.

@cracked: the engine will never shut off. This is my brain where this amazing idea was generated.

@ALL: I will now explain it. Most senior drivers don't believe my this invention and the secret I revealed to them.
Energy can be produced from many things and we can transform energy from its one form to another. When we run car on plain road, the engine requires energy to run against gravity. Gasoline is burnt in combustion chamber and energy is produced which forces pistons and ultimately our car moves. If we cut-off fuel supply then car will stop, because the engine has no force left to go against gravity to produce motion.
On downslide why your car runs without pressing accelerator? This is because you are already going with the force of gravity which is not in the case when you are driving on plain surface. At this stage car pistons don't require fuel to produce force. You are already using gravity for moving the car. Here I introduce my amazing technique. Your car is initially on CNG when you start downsliding, turn your car on petrol and immediately turn it to neutral. You disengage fuel supply now. The engine will not shut down, it will keep working with the force produced by its own motion due to gravity. About gear shifting, you can drive car neutral, but it is very dangerous in car handling and braking. So it is advised to shift gears according to speed.

No one asked that how AC, brakes, power steering, headlamps, hi-end stereo component will work without fuel

Believe me this technique is not only for Bilal's Mehran. Come to me and I will prove my words and your car, headlamps, AC, Power Steering, power brakes, hi-end stereo component, all these things will be working without any fuel.
Bhai sab kuch tu aap ki garri ka chala dia hay muft mein, aub bhe yakeen na aiey tu chalao petrol par mujhay kia

[alkandar]

Yes engine and gears are more precious, but you will not harm them as along as you are keeping below the red line and you are doing it smoothly, not jerking the system too hard. In local cars i'd suggest at least 1,500 RPm below the redline would be ok.

Completely wrong assumption. The revving of engine without pressing the accelerator pedal does not equal more fuel consumption.

Actually, it might be even less than idling.

You see, when you are accelerating at a high RPM, the power of the engine is being delivered to the wheels through the clutch and transmission, the power of the engine comes when you burn fuel, hence more fuel consumption.

On the contrary, when you are going down hill, while the clutch is engaged (pedal not pressed, car in gear, not neutral), it is not the burning of fuel that is revving the engine, it is the force of gravity and your forward momentum that is moving your wheels which are connected to your crank shaft through the clutch and transmission. So here the gravity and forward momentum is causing high RPM, not fuel.

This is why we have better fuel consumption while going downhill and on the highways, even with high RPMs.

Correct me if I am wrong.

++1 (we reduce the speed by useing
Compression of engine) no more fuel consumption

[talhawaleed]

I don’t understand that what is the fuss about de accelerating your car on gears. I have always been using gears to slow down my cars even once I am not driving on the hills. My previous car which I sold was Khyber and I have always slowed it down using gears and my friends at times used to say that your excessive de-accelerating your car on gear may damage your car engine but I sold that car after driving it for two lac and twenty four thousand kilometers and never faced any issues with the engine.

I believe that most of the good drives uses gears a lot to de-accelerate their cars at higher speeds and on slopes. It’s a matter of an habit which puts you in more control over your cars. Now it’s my habit to use a gears a lot in order to slow down my car but never faced any issues and never noticed an increase in fuel consumption. Even while driving back from murree I had always used my gears to control my car but never saw that in any way that has an impact on my fuel economy. I can assure you this for cars such as corolla 2007, Liana and Honda City 2007.

[Skill]

Lucky bilal you are always running your car on the petrol which is retained inside the carburator but remember whenever the fuel runout inside the carburator and you have to overtake some vehicle in a hurry you will have to push the gas padal because though the engine parts ie pistons c/r rods and crank shaft moving with the tyre's momentum but not giving you boost and to get you boost you need fuel and that moment running short of the fuel may cause problems so i suggest safety first.

[2c]

This is not relevant to topic but ever tried going down in neutral its extremely fun

ill bet you 1k if you do that in LDA parking plaza and make a video

[capsat]

[I]Bilallucky your technik is hard to buy, power steering need hydraulic pressure & brake booster need vaccum from intake manifold if engine is not 'IDLING on whatever fuel' how would vehicle be conveniently controlled.

I drive from KHI to Muzzaffarabad round trip twice a year for down hill journey using 'engine' at mostly idling revs to manage control with minimum of brakes,

anyone else tested such tech to support bilal???? [/I]

[fahadwizz]

Common guys! Using engine braking power downhill your car will not consume any more fuel than it will consume while idling. And as long as you don't jerk it wont have impact on engine wear. Make sure you don't press too much clutch!

[isi0000]

When i was learning driving my teacher told me that at high speeds use engine to stop the car and use brakes less and also my father used to tell me the quote couple of times that a good driver never uses brakes