Engine braking

Doug the D

I thought I'd create this thread due to the severe derailment of the funny photo thread over in GC.

Engine braking was being discussed and whilst I'm more than happy with some of the responses, I thought it might make sense to discuss it in more detail here (someone did suggest it should be discussed here too, due to a lack of funny photos!).
Having driven for almost 22 years and being an advanced driver and a driving assessor, I think I'm fairly qualified to have a sensible opinion on this practice. If this post comes across as preachy or sucking eggs to some members that are experienced drivers, then I apologise, but this isn't really aimed at you I put it here as info for new drivers, or those that are happy to learn new things.

Engine 'braking' as a term is commonly misunderstood ime. The reason for this is that it has the word 'braking' as part of the term, when in actual fact, the only thing that should ever be used to slow a car is the brakes.

Here is a list of reasons not to slow a vehicles speed using the gears, it's not exhaustive, but covers most points:
When engine braking, only the drive wheels are slowing the car. Unless you have a 4 wheel-drive car, this means that only the front (usually) or rear pairs of wheels are doing the hard work of slowing down a car. Not only is this much less effective at doing this job, it can also cause wheels to lock (ABS does nothing if the brakes aren't used). This could clearly cause a loss of control of the vehicle.By not pressing the brake pedal, there is also something else really important that is not being used - the brake lights. By engine braking into corners or towards any hazards, you are not telling the cars behind you that you are slowing. Clearly the implications of this are at best, a narrowing of the gap between yourself and any following cars, or at worst, a rear end shunt. If you are entering a corner, turning the wheels to do so and get rear-ended, you will lose control of the vehicle.Changing gear whilst dealing with hazards is not ideal. I know lots of drivers don't drive with 2 hands on the wheel, but there's a reason we should...Changing gear requires 1 hand to be removed from the wheel to do so.The correct way to engine brake is to utilise a gear lower than would be usual in certain circumstances. The most obvious one that I can think of is this; You are driving at 30mph in a town, in 3rd gear. You approach the crest of a hill and are about to drive down the hill. At this point, changing into 2nd gear allows the engine to retard the speed of your car and hold it at around 30mph, whereas to remain in 3rd would allow gravity to do it's thing and speed your car up. If you stayed in 3rd, you would have to brake gently, when it's unecessary if you use the correct gear at the correct time.

As a driving instructor posted in the earlier mentioned thread:

'Gears to go, brakes to slow'

DOBLY

Good advice - how does this work for electric cars without gears?

Frostytouch

Good question, most Nissan and others have a B mode that retards the car in a similar way. Basically increases the energy recovery level and slows the car.

Hyundai EV cars have paddles so you can select level 1,2 or 3 (plus zero)...just pick level 3 on a major downhill - mine recovers up to 1 mile on a big hill.

nvingo

When approaching a corner or lower speed limit, the driver behind shouldn't need your brake lights to remind him to select the appropriate speed.

Leo31291

Don't be a fool and break the two second rule

I judge the road ahead, if I see cars braking in the distance I ease off the accelerator and utilise engine braking that way. If there's a set of traffic lights on red down the road I'll do the same. Obviously if someones right on my bumper I won't do it but it's up to the cars behind me to keep a safe distance and read the road.

John7

A good driver should be able to regulate the speed of a car by using a combination of braking, throttle control and/or engine braking. It is not always necessary to use the brakes to slow down. Simply lifting off the throttle or slipping down a gear is a useful practice.

There are far to many people on the road who cause annoyance to the cars behind by constantly touching the brakes when completely unnecessary. All thats needed is to lift off the throttle in most cases.

If following vehicles are reliant on brake lights to moderate their own speed, they need to go back to driving school!

I now drive a self charging hybrid and actively use regenerative braking to modulate the vehicle speed to maximise fuel economy. In my days of driving manual boxed cars, I would use enging braking when appropriate, selecting the correct gear to suit the road conditions and speed required. I have been driving 41 years.

I recently discovered that my wife’s sister slips her automatic car into neutral when going downhill in the mistaken belief this would maximise fuel economy! Needless to say I was horrified and explained to her that this was an extremely dangerous practice and should cease immediately.

LV426

It may interest you to know that - at least as far as my EV is concerned - the car makes up its own mind whether to apply the brake lights.  At higher levels of regeneration/deceleration, they come on, whether it's achieved through "foot off the loud pedal" (e.g. when set to max regen) or use of the brake pedal.  

And note also that use of the brake pedal does not imply use of the friction brakes either; it means "decelerate" to the car and the car will decide the most efficient and effective way to go about that depending on speed and how hard you are pressing, etc.  Mostly and in normal (as opposed to "emergency") situations, it's regenerative, with very little use of the pads and discs.

In other words - it makes absolutely no difference which controls are used and which settings are set;  when you ask the car to decelerate or retard or coast or whatever at any given rate and at any given gradient, it makes no difference how you (as driver) make that request - by adjusting the retard level or by carefully holding the accelerator or brake pedal or whatever; the way the car achieves any one given rate of coast or deceleration (and, in fact, light acceleration on a downhill) is achieved by the car with exactly the same use of the motor - the same draw on or regen to the traction battery, the same (usually non-) use of the friction brake and the same application of the brake lights.

And yes, in these circumstances, it will be the driving wheels that do all the work.  Hence the advice given earlier about how and when (not to) use engine braking becomes totally irrelevant and actually impossible for the driver to manage.

MarkyPancake

Engine braking is very useful on motorbikes. Particular with each gear having such a large rev range you can make use of.

Bl4ckGryph0n

I always thought only that part refers to engine braking anyway A technique which is very useful to ensure your actual brakes still work when you really need them

cosmicma

i suppose it depends on the car
my wifes BMW Xdrive 8 speed auto thingy will coast/freewheel in ECO mode at 30mph and above as soon as you lift your foot off the accelerator
if you want to slow down you have no choice you have to use the brakes which re engages the gearbox and engine braking occurs until you press the accelerator again and once you lift your foot off it will coast again
in sport mode the gearbox is always engaged in an appropriate gear and engine braking occurs at all speeds as soon as you lift your foot off the accelerator  

i can honestly say i have never had the drive wheels lock up due to engine braking in any car iv'e driven but i get the part about ABS being non functional if only gears are used to slow down if they did decide to lock up but i think you would have to be doing something drastic with the gearbox for that to happen in normal conditions