Engine Braking

[Praveen_Auto]

 

Engine breaking helps saving breaking machanism in our vehicles thus improving its life. Also engine breaking has its advantages when traveling downhills and slopes.

 

My question, is there any benefit in doing this (engine breaking) while traveling in heavy traffic.?? (as the chances are high where you need to depress brakes padels more often)??

 

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Edited April 2, 2019 by Davy
Corrected misspelled topic title.

[CNX]

14 minutes ago, Praveen_Auto said:

 

Engine breaking helps saving breaking machanism in our vehicles thus improving its life. Also engine breaking has its advantages when traveling downhills and slopes.

 

My question, is there any benefit in doing this (engine breaking) while traveling in heavy traffic.?? (as the chances are high where you need to depress brakes padels more often)??

 

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I can't see any benefits of engine breaking. Besides being costly to repair, it can potentially kill you when traveling downhill or on slopes due to loss of steering & brake power and will be a real hassle if happens in heavy traffic.

[Magnum]

2 minutes ago, CNX said:

I can't see any benefits of engine breaking. Besides being costly to repair, it can potentially kill you when traveling downhill or on slopes due to loss of steering & brake power and will be a real hassle if happens in heavy traffic.

Engine braking automatically takes place when you take your foot off the pedal in gasoline vehicles. In diesel vehicles engine braking is evident mostly in vehicles with DPF due to return pressure from the exhaust.

Also I have noticed some transmissions automatically downshift when you are coasting downhill.

To answer the OPs question, you need to build up some speed for engine braking to happen so I don't think it's possible to do it in heavy traffic

[top tip]

Engine braking is mainly used when travelling downhill, in sri lanka the ideal situation would be driving down from nuwara eliya or places like haputale-beragala. The main purpose of engine braking is to prevent your brakes from overheating because after a certain temperature brake pads starts to slip from the disc as well as the brake fluids start to overheat and components like washers get damaged. Also you can reduce excessive wear and tear of brake discs. With engine braking you could perform a much controlled drive downhill because together with some slight braking (blend braking) it does least harm to the vehicle but remember to keep the revs under around 3000.

You could take advantage of the build of speed rather than letting the vehicle coast in neutral in order to do a controlled decent. This time would be ideal to make your A/C work at the maximum level because the engine is being mechanically revved without any throttle inputs.

According to my experiences engine braking is most effective in a manual gear vehicle compared to automatic due to the clutch. The speed is directly fed to the engine without any losses in speed. Whereas automatic felt a bit light revving and had a coasting feel, this may be due to high gear ratios found in a four speed automatic.

But on a traffic scenario I don't understand because anyway you have to exceed a certain speed on a given gear to induce a braking effect once you let go of the accelerator. Plus engine braking ain't effective for sudden braking, in simple it is something used to maintain speed.

[PreseaLover]

What I noticed in my car was quite the opposite. before doing a hillside trip, i replaced brake pads, rears abs, new drums, new tyres. When going down the hill at the start I figured that I had to trample the brakes harder and deeper. I checked the brake fluid level too and it was the same. and after sometime it was normal once again. I thought i was losing brakes, so i had to go real slow for sometime. whats the explanation for this?

[kush]

30 minutes ago, PreseaLover said:

What I noticed in my car was quite the opposite. before doing a hillside trip, i replaced brake pads, rears abs, new drums, new tyres. When going down the hill at the start I figured that I had to trample the brakes harder and deeper. I checked the brake fluid level too and it was the same. and after sometime it was normal once again. I thought i was losing brakes, so i had to go real slow for sometime. whats the explanation for this?

New brake pads/ liners take time to cure and set in and take will take couple of hundred Km to get in to their full performance.

This is why it is recommended that you take it easy during this time as brake fade what you have experienced could happen if with continuous use as they overheat.

 

[kush]

Engine braking is using internal friction of the engine to slowdown, this is what you experience when you lift off your foot from the accelerator. Amount of friction available will depend on the type of engine. If used properly there is potential saving on fuel and wear and tare in braking components.

You need to anticipate the traffic conditions and use the throttle to manage the speed, in a manual you could down shift and in auto use 3,2,1/L/S (for slope) as applicable for each vehicle. When down shifting you one should take care not to over rev the engine.

This is no alternative to brakes but a supplementary technique. This will not bring the car to a full stop hence you will need to use normal braking in emergencies/ driving in heavy traffic etc..

 

 

 

 

[varotone]

I don't understand how to use engine braking in traffic. May be in light-to-light traffic where there's traffic before the traffic lights but not after. You can accelerate when it turns green and instead of slamming the brakes when the next light is red, you can use engine braking. Ride will be smooth. (Boring if the car is under powered)

Engine braking is essential in mountainous terrain. Coasting in neutral or with clutch depressed in haputale-beragala is calling for disaster. If you slow down the car only with the brakes, brakes might have already failed due to heat when you want to come to a stop. 

When engine braking, rotation of the crankshaft compresses the air and energy is dissipated as heat. No fuel is consumed. Your battery is charged and ac works basically without burning fuel. You don't get this if you coast downhill.

Also, engines are built to dissipate heat. Brakes are not. (Except for performance cars with brake ducts). Engine braking is essential.

[Hoonigan]

5 hours ago, kush said:

Engine braking is using internal friction of the engine to slowdown, this is what you experience when you lift off your foot from the accelerator. Amount of friction available will depend on the type of engine.

It's not friction but compression. There's a huge industry built around reducing internal friction

 

[kush]

1 hour ago, varotone said:

Also, engines are built to dissipate heat. Brakes are not. (Except for performance cars with brake ducts). Engine braking is essential.

Brakes are designed to dissipate heat, that is why most of them are vented (at least front) and wheels have holes in them to allow are flow to brakes at expense of poor aerodynamics.

Performance cars use exotic materials which do not fade due to better thermal properties

 

 

 

[Magnum]

8 hours ago, PreseaLover said:

What I noticed in my car was quite the opposite. before doing a hillside trip, i replaced brake pads, rears abs, new drums, new tyres. When going down the hill at the start I figured that I had to trample the brakes harder and deeper. I checked the brake fluid level too and it was the same. and after sometime it was normal once again. I thought i was losing brakes, so i had to go real slow for sometime. whats the explanation for this?

Probably your brake distribution between front and rear brakes went out alignment after you replaced those components. The brakes adjusts itself after using it for sometime. 

[varotone]

22 hours ago, kush said:

Brakes are designed to dissipate heat, that is why most of them are vented (at least front) and wheels have holes in them to allow are flow to brakes at expense of poor aerodynamics.

Performance cars use exotic materials which do not fade due to better thermal properties

1

Are the holes in the rims designed to draw air in to cool the brakes? I thought they are to save the cost of materials and reduce the weight, and rotational inertia. I've also seen many rims without holes or tiny holes.

[kush]

3 hours ago, varotone said:

Are the holes in the rims designed to draw air in to cool the brakes? I thought they are to save the cost of materials and reduce the weight, and rotational inertia. I've also seen many rims without holes or tiny holes.

Designed for all that and the looks

 

[Hoonigan]

On 4/5/2019 at 2:32 PM, varotone said:

Are the holes in the rims designed to draw air in to cool the brakes? I thought they are to save the cost of materials and reduce the weight, and rotational inertia. I've also seen many rims without holes or tiny holes.

Some wheels are designed to assist in cooling while some are designed for improved aerodynamics. But most are for aesthetics. But it was rightly pointed out that the brakes are in fact designed to dissipate heat. The vented, grooved and cross drilled rotors all perform this task. Even the most basic rots do this with the exposed area. And some, if not most, cars have cooling ducts from the bumper to the inner wheel well liners to help dissipate heat.