Engine braking - OK or not OK? (4 Viewers)

[roxburd]

Hi all,

Do you use engine braking in your motorhome? I find myself using it a little from time to time and I suspect it's frowned upon by HGV instructors... but I've never had any instruction so I'm curious. I'd never driven a big diesel before last month. I've done the IAM motorcycle advanced test and they have a saying - brakes to slow, gears to go. It basically means that you shouldn't use engine braking. They also advise block-changing - changing to the gear you want all in one go, rather than changing one gear at a time and declutching between. And not changing gear at all until you've finished braking. It all depends on circumstance but they are general guidance points.

I try to drive my MH at a very leisurely pace - but I'm still occasionally tempted to use a little engine braking - for example, as I'm entering a roundabout with a little more speed than I'd like to carry round and the gear I want will give some braking.

I realise this might seem a bit 'who cares' to some but I've found myself wondering and so thought I'd see what people think... I suppose the important question is this: can gentle engine braking cause any mechanical issues?? I wouldn't have thought so...

Cheers
(let the disagreements commence)

 

[tacr2man]

HGV use engine braking extensively they are even fitted with devices to increase effectiveness eg , exhaust brakes and jake brake many also auto shift down gears when operating the engine brake to maintain high rpm

 

[bigtwin]

If so, then advanced driving would suggest that you brake to a stop or appropriate speed for roundabout using brakes rather than gears, then select gear for that speed, matching road speed to engine speed. On downhill descents then gears to utilise engine compression to slow.

This is exactly it.

In all other instances being in the correct gear for the prevailing circumstances should, in most instances and combined with good forward observation and anticipation, provide adequate braking simply by lifting (rolling off) the throttle such that the brakes don’t even come into play.

However, many bikers usually ride in one (and often two) gears too high thus necessitating more brake application than is necessary.

Ian

 

[autorouter]

Descending a long steep pass in a heavy vehicle, it's all about dissipating the energy that it acquired by ascending to the top of the pass. The engine can waste that energy, and it is built to get hot and lose heat, so it won't have a problem doing that. If you dissipate all the energy in the brakes, they will get extremely hot - hot enough to boil the brake fluid and reduce the pad friction, which can be dangerous.

When driving down a long descent, if you are speeding up with no throttle applied you are in too high a gear. Brake and change down. Keep an eye on the rev counter, and decide the maximum you will let it increase to. You can let the revs increase until the speed stays constant with no throttle. If the rev counter is getting too high, brake and change down again. You should aim to be descending with high but reasonable revs, at a constant speed without using the brakes.

If the slope eases off, you can change to a higher gear. With practice you can get down a long steep descent hardly using the brakes, except when changing down or going round hairpins.

I find on motorways I sometimes need 3rd gear, never 2nd. Off the motorway on mountain roads 2nd gear is not unusual. I was told to go down a hill in the same gear you would use to go up it.

I learned all that with my first motorhome, a converted ambulance with a 4 litre Austin petrol engine and a crash gearbox that needed double declutching on all gears.

 

[Marie-Claire]

Engine braking always , I just roll upto a junction looking for the gap I need then accelerate away in the correct gear, it also creates a gap in front of you as the cars roar upto the junction then slam the brakes on. A lot of trucks these days shut off the diesel when you come off the throttle . The Thelma retarders were excellent on the prop shaft but they only seem to be popular on coaches.

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[Shrimp]

I always used engine braking with my motorbikes and very often didn’t bother with the clutch changing gear.
I engine brake in the car and probably would in the MoHo, but I don’t drive that, I do change from 3rd to 5th in the car as there is little difference except in the revs!
I was always told, engine brake if you can.

 

[St3v3]

. A lot of trucks these days shut off the diesel when you come off the throttle .

Most, if not all, vehicles these days will do that. It's called overrun fuel cut (OFC)

 

[funflair]

Engine braking always , I just roll upto a junction looking for the gap I need then accelerate away in the correct gear, it also creates a gap in front of you as the cars roar upto the junction then slam the brakes on. A lot of trucks these days shut off the diesel when you come off the throttle . The Thelma retarders were excellent on the prop shaft but they only seem to be popular on coaches.

They actually shut off the exhaust to increase engine braking (exhaust brake), Telma retarders are an option on IVECO daily based motorhomes and are brilliant we have one and would spec it again and again.

 

[funflair]

Descending a long steep pass in a heavy vehicle, it's all about dissipating the energy that it acquired by ascending to the top of the pass. The engine can waste that energy, and it is built to get hot and lose heat, so it won't have a problem doing that. If you dissipate all the energy in the brakes, they will get extremely hot - hot enough to boil the brake fluid and reduce the pad friction, which can be dangerous.

When driving down a long descent, if you are speeding up with no throttle applied you are in too high a gear. Brake and change down. Keep an eye on the rev counter, and decide the maximum you will let it increase to. You can let the revs increase until the speed stays constant with no throttle. If the rev counter is getting too high, brake and change down again. You should aim to be descending with high but reasonable revs, at a constant speed without using the brakes.

If the slope eases off, you can change to a higher gear. With practice you can get down a long steep descent hardly using the brakes, except when changing down or going round hairpins.

I find on motorways I sometimes need 3rd gear, never 2nd. Off the motorway on mountain roads 2nd gear is not unusual. I was told to go down a hill in the same gear you would use to go up it.

I learned all that with my first motorhome, a converted ambulance with a 4 litre Austin petrol engine and a crash gearbox that needed double declutching on all gears.

We went to Madeira a few years ago, (they have some serious hills there) we were doing a walk at the top of the island so we all piled in a mini bus and the poor thing crawled it's way up in 1st and second gear mostly, we came down in the same gears and the brakes were hardly warm

 

[poppycamper]

So how do you use engine braking ?

What type of engine braking? IMO there are two sorts..
Proper engine braking when absolutely vital, I.E. descending steep hills or the other sort which I would better describe as going down through the gearbox to slow vehicle when approaching junction, roundabout, sharp bend etc...
I use the later all the time and as such very rarely need use of brakes...

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[chaser]

Never ever driven one and don't intend to but don't these electric cars use engine braking to charge the battery?

 

[PP Bear]

Not read the thread, so probably been said already, but….

As my HGV instructor said, your brakes your friend, not the gearbox and associated assemblies

Lots cheaper to replace pad and discs and it’s not a competition to see if you can make them last longer. Use them as designed as the tiny clutch and drive shafts don’t really want all that weight and kinetic energy being forced through them, just to slow down.

Heavy hill descents is another matter, but low gear and slow speed are best for me and cadence braking, to prevent the heat buildup wherever possible.

All my own option, but it’s how I was taught on the artics and reinforced throughout my career.

 

[suavecarve]

That's the problem.... you need to use brakes to initially slow down and then select lower gear at correct speed AND THEN use engine braking to stop vehicle from going any faster... if it does and starts over reving engine.. brake to bring speed back down..

Totally agree.

 

[St3v3]

Never ever driven one and don't intend to but don't these electric cars use engine braking to charge the battery?

Yes.

. Use them as designed as the tiny clutch and drive shafts don’t really want all that weight and kinetic energy being forced through them, just to slow down.

They seem to be perfectly well specified for accelerating. Engine braking "power" is far less.

.... and cadence braking, to prevent the heat buildup wherever possible.

Cadence braking is much more rapid and used before ABS existed, allowing some slowing whilst maintaining the ability to steer. But, yes, on and off the brakes is good. If you change gear you'll have to brake even less

 

[Coolcats]

Never ever driven one and don't intend to but don't these electric cars use engine braking to charge the battery?

EV’s do not have engines but they do have Motors and yes you are correct some but not all do have regenerative braking

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[tinkertaylor]

Approaching Islands and junctions I normally roll to a stop in neutral, if possible. I leave a big enough space in front of me to stop me using my brakes and or engine to slow me.

Brakes and engine braking is just wasting fuel, leave a space and roll into it. MPG is increased (its how car manufacturers get there mpg figures so low)

Same on motorway in congestion, let the morons follow each other nose to tail breaking and accelerating, rinse and repeat. I stay stationary let a gap form then 1st gear and just roll along, hopefully not having to brake. You do get morons filling the space in front of you put usually when the other drivers see what your doing they catch on and join in the relaxing traffic jam driving style, just leave a gap.

 

[Coolcats]

This thread is making me chuckle, engine braking should be used in context so yes a large heavy vehicle with a diesel will benefit and as some have said are designed for engine breaking. On the other hand a a powerful high reving performance engine with a lightweight flywheel and a lightish vehicle if you use engine braking on that you will probably land up in the kitty litter on track.

 

[poppycamper]

This thread is making me chuckle, engine braking should be used in context so yes a large heavy vehicle with a diesel will benefit and as some have said are designed for engine breaking. On the other hand a a powerful high reving performance engine with a lightweight flywheel and a lightish vehicle if you use engine braking on that you will probably land up in the kitty litter on track.

I based my replies in response to the OP's First post, First line..."Do you use engine braking in your motorhome"
Never seen a high reving performance engine with lightweight flywheel in a lightish motorhome..!!!

 

[chaser]

To be honest, I don't know what else you can do, you lift your foot up and you start slowing down. How would you avoid this?

 

[The Old Man]

Last year in our Ducato motorhome I went down loads of hairpin strewn, steep Alpine passes in Germany, Austria and Slovenia. I don't see how you can descend safely without getting into a lowish gear to get some engine braking.

Porlock Hill and Countisbury Hill! I cannot drive the Motorhome down either without engine braking.

Porlock especially if I try to decend just on the brakes, the brakes get so hot and smelly I worry if like the old style brake linings, they will cease to work and even catch fire?

On Porlock, the last section I take in First gear and brakes, the noise is painful but...

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[Jimbohorlicks]

Some of the down hill grades we came across in Morocco required engine braking otherwise the brakes would have been worn out very quickly or burnt out. Plus its also good to get those higher revs for a regen and clear out .

 

[Coolcats]

I based my replies in response to the OP's First post, First line..."Do you use engine braking in your motorhome"
Never seen a high reving performance engine with lightweight flywheel in a lightish motorhome..!!!

Absolutely, I guess there is a first time for everything But there is context in that technique for one type of vehicle is not applicable to all. So yes engine braking for a MoHo is a justifiable technique

 

[Coolcats]

To be honest, I don't know what else you can do, you lift your foot up and you start slowing down. How would you avoid this?

Ballence…..you ballence the peddle between accelerating. Steady speed and slowing down (breaking) with your foot off…it’s like driving a dodgem

 

[Bramidan]

Not heavy traffic or indeed urban driving but on my long journeys with cruise control set my 9 speed auto box changes down. Thus it utilises engine breaking.
Many many years ago coming off the M40 at Loudwater (Bucks) I used to stick my manual car in neutral and see if I could coast down the slip road to the first roundabout, even used to blow on the windscreen to convince the kids it helped!
Different times!!!!!!!

 

[dawsey]

Descending a long steep pass in a heavy vehicle, it's all about dissipating the energy that it acquired by ascending to the top of the pass. The engine can waste that energy, and it is built to get hot and lose heat, so it won't have a problem doing that. If you dissipate all the energy in the brakes, they will get extremely hot - hot enough to boil the brake fluid and reduce the pad friction, which can be dangerous.

When driving down a long descent, if you are speeding up with no throttle applied you are in too high a gear. Brake and change down. Keep an eye on the rev counter, and decide the maximum you will let it increase to. You can let the revs increase until the speed stays constant with no throttle. If the rev counter is getting too high, brake and change down again. You should aim to be descending with high but reasonable revs, at a constant speed without using the brakes.

If the slope eases off, you can change to a higher gear. With practice you can get down a long steep descent hardly using the brakes, except when changing down or going round hairpins.

I find on motorways I sometimes need 3rd gear, never 2nd. Off the motorway on mountain roads 2nd gear is not unusual. I was told to go down a hill in the same gear you would use to go up it.

I learned all that with my first motorhome, a converted ambulance with a 4 litre Austin petrol engine and a crash gearbox that needed double declutching on all gears.

This is the clearest explanation of when and how to use engine braking.

I haven’t seen much reference in the thread on the reason why it is absolutely so important to still use engine braking in long descents if you are in a motorhome. Weight.

Your vans are usually running right at the very edge of the limit of what the chassis and the brakes it uses were designed and specified for. As drivers of such limit-vehicles we therefore must exercise extreme caution, common sense and of course deploy engine braking on any long downhill descent. The longer the descent, the more engine braking is needed. It is why there remain signs all over Europe reminding “use engine braking”. These signs are targeted at heavily loaded vehicles at their limits - that’s fully loaded HGV and, yes, us.

As an ignorant 22year old I cooked the brakes descending an Alpine switchback in my first camper. It means you lose your ability to brake altogether. 3rd wasn’t enough. The only way I was able to slow enough to make it round the next switchback was to smash the box into 2nd with the van accelerating, dump the clutch and hope both clutch engine didn’t blow which thankfully they didn’t. The over speed did wreck the vacuum pump though. It was one of the most frightening experiences I ever had. Even when they cooled down the wrecked pump meant no brakes. The rest of the descent was in 1st.

Modern stuff is way better, but a very heavily loaded van can still easily cook its brakes on a long descent. If anyone reading this seriously does not know how to use it, which would amaze me given the experience level in here, the best advice is to learn and practise. It could actually save your life.

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[L' Hobo]

On my Morris Minor ( first car) if you didn’t use engine braking you didn’t stop

That applied to the old drum braked Trucks & Coaches too!
I remember the 6 legger Bedford (Val?)Coaches, one had to drop them a couple of cogs before one stood any chance of stopping!
At least they didn't have a crash box!

 

[bigtwin]

They seem to be perfectly well specified for accelerating. Engine braking "power" is far less.

Agreed.

Cadence braking is much more rapid and used before ABS existed, allowing some slowing whilst maintaining the ability to steer.

Agreed.
Implicit in the use of the term for braking is a short ‘mark-space’ ratio (i.e. emulating ABS). Strictly speaking @PP Bear’s use of the term meets the definition of cadence but has such a long mark-space ratio that it is out of context in terms of what is meant by cadence braking.

Ian

 

[SpeedyDux]

So how do you use engine braking ?

ComfortMatic software does the downshifts automatically when braking on a downhill stretch of road. You get used to the high revs and noise. Nothing to worry about. The diesel engine is acting as an air compressor to absorb kinetic energy and supplement the hydraulic brakes.

With my hybrid car, selecting "B" mode uses the electric generator motor to do most of the downhill braking. The recovered kinetic energy goes into the HV battery.

 

[autorouter]

Just to add some numbers to it, a 3000kg motorhome descending 500 metres needs to lose energy. The amount of energy is 3000 x 9.81 x 500 = 14,715,000 joules, or 14715000 / 3600 = 4087.5 Wh.

If that descent takes 15 minutes, the average power dissipated by the engine/brakes is 4087.5 x 4 = 16,350W, ie 16.35kW. So imagine your brakes being heated by four 4kW heaters. That's why they get hot.

On the other hand, wouldn't it be nice if all that lovely energy could go into charging your batteries.

 

[robnchris]

In my younger days I rode a bit of Speedway and Grasstrack, no need to worry about when to use the brakes on those bikes.

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[seasideBill]

Not heavy traffic or indeed urban driving but on my long journeys with cruise control set my 9 speed auto box changes down. Thus it utilises engine breaking.
Many many years ago coming off the M40 at Loudwater (Bucks) I used to stick my manual car in neutral and see if I could coast down the slip road to the first roundabout, even used to blow on the windscreen to convince the kids it helped!
Different times!!!!!!!

Yes, I’d noticed that, Recently made the change from manual to 9 speed auto which utilises engine braking in situations where I’d habitually use the brakes.