I noticed that using the engine brake on the Actros ('18) doesn’t do much…In fact it will reduce speed much much faster with just the foot brake compared to max engine brake + same pressure on foot brake . I used to use it all the time (the engine brake ) when coasting towards roundabouts on a down slope (99% of them) as it likes to pop out of gear 0.1 seconds after you realease the acc. The only downside is it looks like my fuel consumption has gone up a bit but I’ll need more time to confirm
I wonder if other makes are like that except DAF which has an outstanding engine brake I use it 99% of the time as it can nearly bring the truck to a roundabout speed from 56mph.
Any downsides to excessively using the engine brake ? Have I been doing it wrong all along? (lightly loaded trailers, <10t.) I know it’s only supposed to be used downhill to prevent the vehicle from gaining too much speed but I used to use it every time I needed to slow down and before coming to a stop but it seems on the Actros at least it’s actually increasing my braking distance
Actros engine brake ain’t the best, that’s for sure. It just seems to generate noise and very little else. I’m assuming it’s an auto so if so you need to manually intercede and drop the gears to get the revs into the yellow band for maximum efficiency.
the maoster:
Actros engine brake ain’t the best, that’s for sure. It just seems to generate noise and very little else. I’m assuming it’s an auto so if so you need to manually intercede and drop the gears to get the revs into the yellow band for maximum efficiency.
Yes even at highest setting (3) even when it drops down to 10th or 9th it’s just barely noticeable compared to foot brake alone which also revs the engine but seems much more effective and not only that, braking with foot+engine brake is actually slower which makes it even less useful (except going steep downhills with an empty trailer, then it can hold the speed but put anything on the trailer and the speed will slowly creep up even at max engine brake)
What gears and engine revs are you using for engine braking with the exhaust brake.Anything less than the yellow band won’t cut it.Keep it as close as possible to the start of the red using sequential downshifts on the approach then an exhaust brake will generally do its job, like engine braking without it.It just adds to the engine braking effect but if it’s in the wrong gear there isn’t any either way.
You only need to stand near the approach to any roundabout or junction to know that most/too many drivers have been taught the brakes to slow gears to go method and know no different.
Juddian:
I use it them the time, as said by keeping the revs in the band recommended for maximum effort.
Did he say it’s being expected it to work by it holding a gear no lower than 9th ?.
It’s obvious that the use of engine braking including exhaust brakes isn’t compatible with UK driver training methods which avoid the use of downshifting on the approach and by implication engine braking.
An auto box obviously can’t do that for the driver because it’s blind and therefore doesn’t know if it’s on the approach to any type of obstruction to progress, or hazard or halt.
An auto box obviously can’t do that for the driver because it’s blind and therefore doesn’t know if it’s on the approach to any type of obstruction to progress, or hazard or halt.
Can’t remember what Mercs do, but most modern wagons with autoboxes will auto downshift utilising the exhauster for as long as you need, only needs a press of the appropriate switch, been the case for about 7 or more years on some makes, not as good as a driver selecting the downshift timing themselves if they can be arsed but better than nothing.
I don’t think there’s time on the compressed into a week driver training to cover such things, and on a driving test if you allowed the auto exhauster to stay engaged when speeds drop low enough for 7th or less on a 12 speed box then not only is the downshift quite violent but on a wet road you could see a momentary lock up of the drive axle, no doubt a test fail, too much complication for the new driver on test.
However, such finer aspects of lorry driving should be within the scope of company assessors and trainers to help advise when they appraise new drivers, and when new wagons arrive on a fleet during familiarisation induction for all drivers…that latter was a sarky comment because such famiarisation seldom if ever happens.
An auto box obviously can’t do that for the driver because it’s blind and therefore doesn’t know if it’s on the approach to any type of obstruction to progress, or hazard or halt.
Can’t remember what Mercs do, but most modern wagons with autoboxes will auto downshift utilising the exhauster for as long as you need, only needs a press of the appropriate switch, been the case for about 7 or more years on some makes, not as good as a driver selecting the downshift timing themselves if they can be arsed but better than nothing.
I don’t think there’s time on the compressed into a week driver training to cover such things, and on a driving test if you allowed the auto exhauster to stay engaged when speeds drop low enough for 7th or less on a 12 speed box then not only is the downshift quite violent but on a wet road you could see a momentary lock up of the drive axle, no doubt a test fail, too much complication for the new driver on test.
However, such finer aspects of lorry driving should be within the scope of company assessors and trainers to help advise when they appraise new drivers, and when new wagons arrive on a fleet during familiarisation induction for all drivers…that latter was a sarky comment because such famiarisation seldom if ever happens.
Seems to just add weight to the the uselessness of automated systems.
Is that actually describing a block change down from 12th to 7th let alone without rev matching the downshift first ?.
The exhaust brake is only supposed to be applied ‘after’ each close and most importantly rev matched, downshift far closer downshifts than just dropping from 12th to 7th then dumping the clutch.
Drive axle lock up is predictable if the clutch is re engaged against an idling or incorrectly matched engine on a trailing throttle, let alone if the engine is also being braked at the time when it’s re engaged engaged by an exhauster let alone jacobs.
This all goes to the heart of why synchro, let alone auto boxes can be dangerous.
At best they don’t encourage correctly rev matched downshifts and application of auxiliary engine brakes to optimise engine braking.
While at worse they won’t even allow it.
Then we’ve got the perfect storm of uk brakes to slow gears to go driver training methods added to it.
I think the I shift at least makes a better job of downshifting properly through the gears on the approach.Use of the auxiliary engine braking is obviously then optional added to that.
But locking up under engine braking is generally an issue of dropping too many gears at a time and/or incorrect rev matching before re engaging the clutch against the engine.
I haven’t got a clue how rev matching is done with a Merc auto box but that’s how a truck should always be configured on the approach.The engine brake is only supposed to be applied ‘after’ each downshift has been completed and correctly rev matched.
Although uk driver training seems to have long since forgotten how to drive regardless of gearbox type.
While if an auto box doesn’t allow correct rev matching of downshifts, or holds the engine brake on between downsh shifts, or doesn’t allow for the right gear to maintain the right engine speed, that’s a safety issue because at worse it can obviously create a drive axle lock up or at best it just defeats the object of auxiliary engine braking systems.
That video is pleasure to watch and even better to hear. youtube.com/watch?v=KKnh6DZAcvU
No, not a block downchange that far, that would be ludicrous.
Typically the auto downshifts go down 2 gears at a time.
But, in practice the downshift to 7th can be violent if the exhaust brake is efficient as it is on MANs despite rev matching, obviously the auto system isn’t infinitely variable to suit the road situation of the moment as a competent driver would be.
You were asking about training above, and no i don’t think such fine points of driving could possibly be covered on a typical lorry driving course for a new driver, even same make trucks behave differently let alone the differences between the makes and transmissions.
Anyone who wants to make driving an interesting life will take steps to educate and train themselves about such things once they’ve passed their lorry test and got themselves a job, reading the drivers instruction manual is always a good first step, the info will be in there.
Oh and by the way, i aint by any means brilliant at this stuff, got caught out by a bloody Volvo FM, empty, icy road just approaching the first roundabout after leaving the depot, hadn’t realised the auto retarder had been left on maximum, cue a sudden unwanted/unexpected block downshift just entering the rounabout locked the drive axle solid.
My fault, ages since i’d driven one (my poor excuse) and failed to check the position of the retarder lever, thankfully no damage and got it back under control before it all folded up.
I’m personally not a fan of this auto downshifting, and prefer to control the vehicle myself at all times, but you mentioned about auto retarding on auto boxes and be assured its there on most if not all.
An auto box obviously can’t do that for the driver because it’s blind and therefore doesn’t know if it’s on the approach to any type of obstruction to progress, or hazard or halt.
Can’t remember what Mercs do, but most modern wagons with autoboxes will auto downshift utilising the exhauster for as long as you need, only needs a press of the appropriate switch, been the case for about 7 or more years on some makes, not as good as a driver selecting the downshift timing themselves if they can be arsed but better than nothing.
I don’t think there’s time on the compressed into a week driver training to cover such things, and on a driving test if you allowed the auto exhauster to stay engaged when speeds drop low enough for 7th or less on a 12 speed box then not only is the downshift quite violent but on a wet road you could see a momentary lock up of the drive axle, no doubt a test fail, too much complication for the new driver on test.
However, such finer aspects of lorry driving should be within the scope of company assessors and trainers to help advise when they appraise new drivers, and when new wagons arrive on a fleet during familiarisation induction for all drivers…that latter was a sarky comment because such famiarisation seldom if ever happens.
Seems to just add weight to the the uselessness of automated systems.
Is that actually describing a block change down from 12th to 7th let alone without rev matching the downshift first ?.
The exhaust brake is only supposed to be applied ‘after’ each close and most importantly rev matched, downshift far closer downshifts than just dropping from 12th to 7th then dumping the clutch.
Drive axle lock up is predictable if the clutch is re engaged against an idling or incorrectly matched engine on a trailing throttle, let alone if the engine is also being braked at the time when it’s re engaged engaged by an exhauster let alone jacobs.
This all goes to the heart of why synchro, let alone auto boxes can be dangerous.
At best they don’t encourage correctly rev matched downshifts and application of auxiliary engine brakes to optimise engine braking.
While at worse they won’t even allow it.
Then we’ve got the perfect storm of uk brakes to slow gears to go driver training methods added to it.
I think the I shift at least makes a better job of downshifting properly through the gears on the approach.Use of the auxiliary engine braking is obviously then optional added to that.
But locking up under engine braking is generally an issue of dropping too many gears at a time and/or incorrect rev matching before re engaging the clutch against the engine.
I haven’t got a clue how rev matching is done with a Merc auto box but that’s how a truck should always be configured on the approach.The engine brake is only supposed to be applied ‘after’ each downshift has been completed and correctly rev matched.
Although uk driver training seems to have long since forgotten how to drive regardless of gearbox type.
While if an auto box doesn’t allow correct rev matching of downshifts, or holds the engine brake on between downsh shifts, or doesn’t allow for the right gear to maintain the right engine speed, that’s a safety issue because at worse it can obviously create a drive axle lock up or at best it just defeats the object of auxiliary engine braking systems.
That video is pleasure to watch and even better to hear. youtube.com/watch?v=KKnh6DZAcvU
Rev matching on an Actros gearbox is absolutely spot on because like the ZF they are constant mesh boxes which don’t use the clutch at all other than to start from a standstill, after initial move off all changes up and down are clutchless. The exhaust/engine brake depending on which position you have it on most definitely releases whilst it’s changing up, it will however use the exhaust brake to kill the revs for an upshift.
The standard exhaust brake and engine brakes are pretty poor although much better over 2000rpm, there is an option of the upgraded engine brake, stage 4 on the stalk which is much better, I’m lead to believe, bit don’t know, that it’s actually a Jake but for some reason they can’t call it that in Europe, this is of course standard on the Detroit version in the US but we must pay. Or you can pay even more and order a Voith and then you get stage 4 thrown in.
Rev matching on an Actros gearbox is absolutely spot on because like the ZF they are constant mesh boxes which don’t use the clutch at all other than to start from a standstill, after initial move off all changes up and down are clutchless. The exhaust/engine brake depending on which position you have it on most definitely releases whilst it’s changing up, it will however use the exhaust brake to kill the revs for an upshift.
The standard exhaust brake and engine brakes are pretty poor although much better over 2000rpm, there is an option of the upgraded engine brake, stage 4 on the stalk which is much better, I’m lead to believe, bit don’t know, that it’s actually a Jake but for some reason they can’t call it that in Europe, this is of course standard on the Detroit version in the US but we must pay. Or you can pay even more and order a Voith and then you get stage 4 thrown in.
We know that exhaust brakes need plenty of revs to work properly and you’re saying that it can make all the automated required rev matched downshifts on the approach to achieve that, just like the manual box shown in the video.
Which leaves the question how does it know that it’s approaching a roundabout or a junction to do it and what is the OP referring to and why am I not hearing excatly that happening on the approach to every roundabout and junction whether manual or auto boxes ?.
Bearing in mind brakes to slow gears to go driver training methods.
Rev matching on an Actros gearbox is absolutely spot on because like the ZF they are constant mesh boxes which don’t use the clutch at all other than to start from a standstill, after initial move off all changes up and down are clutchless. The exhaust/engine brake depending on which position you have it on most definitely releases whilst it’s changing up, it will however use the exhaust brake to kill the revs for an upshift.
The standard exhaust brake and engine brakes are pretty poor although much better over 2000rpm, there is an option of the upgraded engine brake, stage 4 on the stalk which is much better, I’m lead to believe, bit don’t know, that it’s actually a Jake but for some reason they can’t call it that in Europe, this is of course standard on the Detroit version in the US but we must pay. Or you can pay even more and order a Voith and then you get stage 4 thrown in.
We know that exhaust brakes need plenty of revs to work properly and you’re saying that it can make all the automated required rev matched downshifts on the approach to achieve that, just like the manual box shown in the video.
Which leaves the question how does it know that it’s approaching a roundabout or a junction to do it and what is the OP referring to and why am I not hearing excatly that happening on the approach to every roundabout and junction whether manual or auto boxes ?.
Bearing in mind brakes to slow gears to go driver training methods.
It’s called Predictive Powertrain Control in a Merc, Volvo call it i-see other manufacturers have different names. It combines GPS with forward facing radar. Using the GPS the truck knows what is coming be it hills, roundabouts, stop signs whatever and will adjust It’s speed and gear changing accordingly, it can see what’s coming up. I’ve attached a clip of a guy out in one with a Merc demo driver being blown away, and who wouldn’t be the first time, in a demo going from 50mph down to 9mph for a roundabout then back to 50 without doing anything other than steering, PPC seeing the roundabout telling him what speed it thinks is correct, in case he disagrees and wants to intervene, the using both engine brake and service brakes slows itself then reaccelerates back to the preset speed. They now know when not to change up into a hill, if you’ve got the cruise at 53 on the motorway and it sees a hill coming as long as the radar doesn’t detect anything in front it will accelerate to 56 into the hill without driver input, or at the top of a hill it comes of the power allowing inertia to take you over the top. It’s all clever if a bit disconcerting at first stuff and available now, at a price. The world has moved on from your 2534 Jeff.
Carryfast:
We know that exhaust brakes need plenty of revs to work properly and you’re saying that it can make all the automated required rev matched downshifts on the approach to achieve that, just like the manual box shown in the video.
Which leaves the question how does it know that it’s approaching a roundabout or a junction to do it and what is the OP referring to and why am I not hearing excatly that happening on the approach to every roundabout and junction whether manual or auto boxes ?.
Bearing in mind brakes to slow gears to go driver training methods.
It’s called Predictive Powertrain Control in a Merc, Volvo call it i-see other manufacturers have different names. It combines GPS with forward facing radar. Using the GPS the truck knows what is coming be it hills, roundabouts, stop signs whatever and will adjust It’s speed and gear changing accordingly, it can see what’s coming up. I’ve attached a clip of a guy out in one with a Merc demo driver being blown away, and who wouldn’t be the first time, in a demo going from 50mph down to 9mph for a roundabout then back to 50 without doing anything other than steering, PPC seeing the roundabout telling him what speed it thinks is correct, in case he disagrees and wants to intervene, the using both engine brake and service brakes slows itself then reaccelerates back to the preset speed. They now know when not to change up into a hill, if you’ve got the cruise at 53 on the motorway and it sees a hill coming as long as the radar doesn’t detect anything in front it will accelerate to 56 into the hill without driver input, or at the top of a hill it comes of the power allowing inertia to take you over the top. It’s all clever if a bit disconcerting at first stuff and available now, at a price. The world has moved on from your 2534 Jeff.
That provides more information but ironically it just seems to confirm what the OP is saying.
I listened with the phones volume as high as possible but didn’t hear the downshifts required to provide for the engine braking script.
In fact didn’t even hear one downshift let alone enough sequential downshifts to get the revs up into the yellow band and hold it there from 5.30 - 5.57.It just sounded to me like it approached the roundabout in the gear it was in until it picked the gear it wanted to accelerate out of it with at 5.59.You could also hear that the exhaust brake wasn’t doing much if anything because the revs were too low.
I would have expected the first downshifts to have been made before it had passed the roundabout sign at 5.40 and well before he’d actually said come off the gas at 5.44 and there was still no downshift made even at that point although there might possibly have been one at 5.50 but obviously too high too late.
There just wasn’t enough time or space there for a proper sequential downshift approach required to optimise engine braking, so how far ahead does the ‘predictive’ control actually read ?.
I think this is what goes to the heart of rollovers and trucks running into hazards and obstructions.
It’s mediocre car driver methods of approach and nothing like the example shown in the American video albeit with a manual box in that case.
If it can see what’s ahead of it then why isn’t it downshifting through the gears in a competent fashion at the right time on the approach to optimise engine braking, just as shown in the US manual box example.
When that’s obviously what the OP is complaining about, insufficient effect of the exhaust brake, obviously because the gear/s being used by the auto box on the approach aren’t low enough if it’s downshifting at all.
As for the tech I don’t get why drivers would be so keen on having the basic skills of the job taken away from them especially when the tech in question won’t possibly match the human eye and brain in control of the vehicle directly connected to it by the limbs.
At least the old 2534 had that in its favour.
Do you know Carryfast I think many of these things come about because we can, it’s also slowly getting both us and the tech ready for platooning and ultimately driverless.
There are I think two comments to be made about the change sequence in the video, one is that by modern thinking serial downchanges are not how it’s done anymore, it might be how we were taught and tend to do it but if you learnt again now it would be different. Brake fade died with drums.
Second we don’t know the detail spec of that unit, we do know that’s it’s an MBUK top of the range 630 demonstrator therefore it will be a tick every box spec so may have a Voith retarder, if so engine speed and gear selection are irrelevant it will give you up to 800bhp of retardation whenever you or the computer ask for it.
Yes Boris brake lights come on with retarders and some engine brakes.
acd1202:
Do you know Carryfast I think many of these things come about because we can, it’s also slowly getting both us and the tech ready for platooning and ultimately driverless.
There are I think two comments to be made about the change sequence in the video, one is that by modern thinking serial downchanges are not how it’s done anymore, it might be how we were taught and tend to do it but if you learnt again now it would be different. Brake fade died with drums.
Second we don’t know the detail spec of that unit, we do know that’s it’s an MBUK top of the range 630 demonstrator therefore it will be a tick every box spec so may have a Voith retarder, if so engine speed and gear selection are irrelevant it will give you up to 800bhp of retardation whenever you or the computer ask for it.
So the brakes to slow gears to go method is programmed into the auto box it won’t sequentially auto downshift on the approach either way ?.
This suggests that whether it’s retarder or exhaust brake it still requires the same correct downshifts to maintain a high engine speed on the approach just the same.If the engine speed is allowed to decay the braking effect is then lost
Carryfast:
We know that exhaust brakes need plenty of revs to work properly and you’re saying that it can make all the automated required rev matched downshifts on the approach to achieve that, just like the manual box shown in the video.
Which leaves the question how does it know that it’s approaching a roundabout or a junction to do it and what is the OP referring to and why am I not hearing excatly that happening on the approach to every roundabout and junction whether manual or auto boxes ?.
Bearing in mind brakes to slow gears to go driver training methods.
It’s called Predictive Powertrain Control in a Merc, Volvo call it i-see other manufacturers have different names. It combines GPS with forward facing radar. Using the GPS the truck knows what is coming be it hills, roundabouts, stop signs whatever and will adjust It’s speed and gear changing accordingly, it can see what’s coming up. I’ve attached a clip of a guy out in one with a Merc demo driver being blown away, and who wouldn’t be the first time, in a demo going from 50mph down to 9mph for a roundabout then back to 50 without doing anything other than steering, PPC seeing the roundabout telling him what speed it thinks is correct, in case he disagrees and wants to intervene, the using both engine brake and service brakes slows itself then reaccelerates back to the preset speed. They now know when not to change up into a hill, if you’ve got the cruise at 53 on the motorway and it sees a hill coming as long as the radar doesn’t detect anything in front it will accelerate to 56 into the hill without driver input, or at the top of a hill it comes of the power allowing inertia to take you over the top. It’s all clever if a bit disconcerting at first stuff and available now, at a price. The world has moved on from your 2534 Jeff.
That provides more information but ironically it just seems to confirm what the OP is saying.
I listened with the phones volume as high as possible but didn’t hear the downshifts required to provide for the engine braking script.
In fact didn’t even hear one downshift let alone enough sequential downshifts to get the revs up into the yellow band and hold it there from 5.30 - 5.57.It just sounded to me like it approached the roundabout in the gear it was in until it picked the gear it wanted to accelerate out of it with at 5.59.You could also hear that the exhaust brake wasn’t doing much if anything because the revs were too low.
I would have expected the first downshifts to have been made before it had passed the roundabout sign at 5.40 and well before he’d actually said come off the gas at 5.44 and there was still no downshift made even at that point although there might possibly have been one at 5.50 but obviously too high too late.
There just wasn’t enough time or space there for a proper sequential downshift approach required to optimise engine braking, so how far ahead does the ‘predictive’ control actually read ?.
I think this is what goes to the heart of rollovers and trucks running into hazards and obstructions.
It’s mediocre car driver methods of approach and nothing like the example shown in the American video albeit with a manual box in that case.
If it can see what’s ahead of it then why isn’t it downshifting through the gears in a competent fashion at the right time on the approach to optimise engine braking, just as shown in the US manual box example.
When that’s obviously what the OP is complaining about, insufficient effect of the exhaust brake, obviously because the gear/s being used by the auto box on the approach aren’t low enough if it’s downshifting at all.
As for the tech I don’t get why drivers would be so keen on having the basic skills of the job taken away from them especially when the tech in question won’t possibly match the human eye and brain in control of the vehicle directly connected to it by the limbs.
At least the old 2534 had that in its favour.
I love the thought of you sat at your desk, notebook in hand making detailed notes about random YouTube videos
acd1202:
It’s called Predictive Powertrain Control in a Merc, Volvo call it i-see other manufacturers have different names. It combines GPS with forward facing radar. Using the GPS the truck knows what is coming be it hills, roundabouts, stop signs whatever and will adjust It’s speed and gear changing accordingly, it can see what’s coming up. I’ve attached a clip of a guy out in one with a Merc demo driver being blown away, and who wouldn’t be the first time, in a demo going from 50mph down to 9mph for a roundabout then back to 50 without doing anything other than steering, PPC seeing the roundabout telling him what speed it thinks is correct, in case he disagrees and wants to intervene, the using both engine brake and service brakes slows itself then reaccelerates back to the preset speed. They now know when not to change up into a hill, if you’ve got the cruise at 53 on the motorway and it sees a hill coming as long as the radar doesn’t detect anything in front it will accelerate to 56 into the hill without driver input, or at the top of a hill it comes of the power allowing inertia to take you over the top. It’s all clever if a bit disconcerting at first stuff and available now, at a price. The world has moved on from your 2534 Jeff.
I love all this tech. The best truck I’ve ever driven was a Volvo FH 540 that I took to Italy to review for a magazine. Being a demonstrator it was loaded with everything and it works faultlessly. Once going set cruise, set gap you want from vehicle in front and set speed you want to come down hills at. It blew me away going over the Alps. The only time I touched pedals was to stop and get going again. It was also Dual Clutch, my favourite feature of any lorry and had that new adaptive steering set up Volvo do, where the resistance is different depending on circumstances. It also made me realise autonomy actually isn’t as far off as I thought
