I have a book about fuel efficient driving made by VTT (Technical Research Center of Finland or something like that). They did simulations on a rolling road dynamometer and also on the road tests with Mercedes and Volvo combinations. Guess which way to change gears was the most fuel efficient?
If you go through all the gears you never get full torque because turbo never has time to reach full boost except maybe at the highest gears.
V8Lenny:
I have a book about fuel efficient driving made by VTT (Technical Research Center of Finland or something like that). They did simulations on a rolling road dynamometer and also on the road tests with Mercedes and Volvo combinations. Guess which way to change gears was the most fuel efficient?If you go through all the gears you never get full torque because turbo never has time to reach full boost except maybe at the highest gears.
Thats interesting, i wonder if it applies to all or just some vehicles (and makers?) depending on fuelling and programming.
I’m thinking of the vast differences to driving say a new 440 Scania and a 430 Axor admittedly designed in different millenia…by the way i prefer the way Axor delivers its power, feels like an old school lorry.
Scania seems to take an age to reach full pulling power, and thats also when resuming power after a period of overrun.
Axor will feel like its giving full power almost immediately in response to throttle and from as little as 800rpm you can hear the turbo spooling up nicely.
Consequently i drive the two different vehicles completely differently, and from your post above could be why…oh and only 8 gears to worry about in Axor which is more than enough given how tractable the engine is.
I would have compared with 440 MAN but can’t think of a single good thing to say about them.
Just being a driver with no technical knowledge I was brought up on Scammell gate change gear boxes and then a self changing gears semi auto box ( not computer managed in the 60s ) then a ZF straight 6 in an Atkinson viewline and along comes the Samson with a 15 speed fuller 5 over 5 with 5 deep reduction ( which I never used ) my training was with Eric the regular driver who had only just got it himself and I watched him for a few minutes and then he pulled in and said " lets see what you can do with it " I was a bit apprehensive with it being different from anything else which I had driven and Eric just said change gear as fast as you can which worked. It soon became apparent that you could skip gears in the right road conditions even running at 80 to 90 tons gross as the gearing was such close ratio’s and keeping up the road speed was more to mind than fuel consumption was. This was something which I used for the rest of my time driving wagons and the newest box I drove was the Merc eps but never one of the fully " atuo " boxes.
cheers Johnnie
Nmm 88s and89s had an almost flat steering wheel much better than the sit up and begs of other motors and far easier to roll your ■■■■ on. Crow.
[zb]
anorak:
For these reasons, magazine roadtesters frequently mention that the manufacturer has told them to blast up to speed as quickly as possible, using full throttle, revs up to peak power and as few gearchanges as possible.
In my haste to beat up Carryfast with his own words I missed this little gem 
That is exactly how it’s done, the energy required to move a lorry from rest to a given speed is the same whether you do it slowly or as fast as possible, as long as you’re in the green band, so you use every rpm, in the green band that you can as you go through the gears and this reduces gearchanges. Accelerating using the least amount of gearchanges reduces the interruption to the power, which loses momentum, which can only be recovered by using more energy, that only comes from using more fuel, so block changing is the most efficient way of accelerating a lorry 
Using every gear in a multispeed transmission is inefficient, even if you keep the engine around its sweet spot (lowest point on the SFC curve) as the fuel saved by keeping the engine in the sweet spot will not compensate for the fuel needed to replace the lost momentum every time you change gear
To further complicate that, in some instances, it is more fuel efficient to change down early and get the engine at peak power, this way momentum is not interrupted and you only need the one downshift, whereas if you changed down as the speed dropped you would lose so much monmentum with each downshift that another one would be required instantly, which uses a lot more fuel and slows progress dramatically
A multispeed transmission is fitted so that for any given speed there is a gear available to keep the engine on the boil, not so you can spend all day jamming gears 
Every single Manufacturer’s Driver I ever spent time with told me that the splitter is only to be used when upshifting, not for downshifting, unless a single split will do, if you need to go down through the box you drop whole gears. These drivers have worked closely with the Engineers who design the lorries in the first place, so there’s a good chance that they know what they’re talking about
To further prove my theory, Volvo has the best autoshift on the market (as proven by the comments on this thread) and it’s I-Shift makes block changes all the way up the box. The whole theory behind the autoshift is to eliminate bad driving practices, so if the best way to go through the box was the way you (Carryfast) say it was, don’t you think that the Volvo Engineers would’ve designed the I-Shift to shift that way instead 
Well Mark thats not quite true any experienced mulispeed with splitter driver will drop that half gear when he knows the motor will take that hill, despite knowing your relationship with the press your works test driver is effectively muzzled by his employers, ie tell them what we want them to know,ours is better than theirs. Crow.
These auto-shift boxes have come in for some criticism regarding low-speed maneouvring etc, but it would be very reasonable to assume that, if you plant your right boot and aim at the horizon, even the most crude of them would know which gear to use and when. Nmm’s previous post, backed up by the best European gearbox manufacturer in the past 50 years, more or less proves the points that everyone on here has been trying to make.
Incidentally, I remember reading at least one report, in which the manfacturer advised revving above and out of the “green”, when accelerating, if it meant another gear could be skipped. Something like that. The opposite to sticking to +/-150rpm of peak torque, anyway.
That was Mercedes I think [ZB]
Crow, I did say that about the single split, bit of a long winded post I know, but it was in there somewhere
The Manufacturer’s Drivers are indeed puppets as such, but their main objective is to make their lorry look good So being as fast as possible actually helps fuel consumption as it makes the most use of free energy (momentum) this is why they drive as they do 
newmercman:
[zb]
anorak:
For these reasons, magazine roadtesters frequently mention that the manufacturer has told them to blast up to speed as quickly as possible, using full throttle, revs up to peak power and as few gearchanges as possible.In my haste to beat up Carryfast with his own words I missed this little gem
That is exactly how it’s done, the energy required to move a lorry from rest to a given speed is the same whether you do it slowly or as fast as possible, as long as you’re in the green band, so you use every rpm, in the green band that you can as you go through the gears and this reduces gearchanges. Accelerating using the least amount of gearchanges reduces the interruption to the power, which loses momentum, which can only be recovered by using more energy, that only comes from using more fuel, so block changing is the most efficient way of accelerating a lorry
Using every gear in a multispeed transmission is inefficient, even if you keep the engine around its sweet spot (lowest point on the SFC curve) as the fuel saved by keeping the engine in the sweet spot will not compensate for the fuel needed to replace the lost momentum every time you change gear
To further complicate that, in some instances, it is more fuel efficient to change down early and get the engine at peak power, this way momentum is not interrupted and you only need the one downshift, whereas if you changed down as the speed dropped you would lose so much monmentum with each downshift that another one would be required instantly, which uses a lot more fuel and slows progress dramatically
A multispeed transmission is fitted so that for any given speed there is a gear available to keep the engine on the boil, not so you can spend all day jamming gears
Every single Manufacturer’s Driver I ever spent time with told me that the splitter is only to be used when upshifting, not for downshifting, unless a single split will do, if you need to go down through the box you drop whole gears. These drivers have worked closely with the Engineers who design the lorries in the first place, so there’s a good chance that they know what they’re talking about
To further prove my theory, Volvo has the best autoshift on the market (as proven by the comments on this thread) and it’s I-Shift makes block changes all the way up the box. The whole theory behind the autoshift is to eliminate bad driving practices, so if the best way to go through the box was the way you (Carryfast) say it was, don’t you think that the Volvo Engineers would’ve designed the I-Shift to shift that way instead
It’s upshifting that we’re talking about not downshifting because it’s all about the best way to accelerate a truck up to speed. It’s actually block changes going down and skip shifting going up if they really must try to turn a close ratio multi speed transmission back into a 6 speed DB box and use it the same way. 
But going down the box whole gears at a time isn’t the same thing as block changes at all though that’s still effectively sequential downshifts but just missing some out on the way down.Block changing means missing out loads of gears to the point where it’s left the same one from like 50 mph all the way down to the speed and gear at which the wagon needs to pull away again having missed out every gear in between,on the basis of brakes to slow gears to go.
The fact is you’re not going to be in ‘the green band’ by taking it up to peak ‘power’ at each upshift.Unless they’re putting the green band in the wrong place.
But using a multi speed close ratio box by skipping gears on the way up,to the point where the engine is taken from the start of it’s torque band up to peak power,in each gear,just defeats the whole object of such boxes which are actually there to allow upshifts to be made over a narrow rev range much closer to the torque peak and well under the power peak just as I’ve said.The former idea would just effectively turn a close ratio box back into a wide ratio one and waste loads of fuel and cause more wear and tear on the engine.Whereas lots of close ratio upshifts,especially using a constant mesh box,go through like lightning actually costing less momentum because the revs don’t need to fall as far during the gearchange,as they would from peak power back down into the torque band as was the case in the old days of wide ratio boxes.
My question is are you actually saying that those engineers have actually programmed a modern close ratio multi speed constant mesh box to follow that idea of of taking the engine up to peak power at every upshift and block change it going down on that basis of gears to go brakes to slow .
Read my post again, for driving in normal conditions, I said the top of the green band, I.E. The top of the peak torque curve, never mentioned the top of the rpm range
And please explain how shifting whole gears and not splitting every gear can be sequential 
Sequential means using every gear one after the other, if you miss out a gear it’s a block change
The part about using the splitter on the way up the box only applies to hills, maybe I never made that clear enough
On the level, this is the recommended shift pattern in a 16spd transmission for a reasonably powered lorry at MGW :- 1lo, 2hi, 4lo, 5lo, 6lo, 7lo, 7hi, 8lo, 8hi. Pulling away in 1st is not strictly necessary, on some lorries that will be the crawler gear, but it’s very good for the clutch. If you don’t use 1st then 2lo to 4lo is the way to do it. On a downhill gradient or in a higher powered or lightly loaded lorry you could also miss out the split into 7hi and go 7lo to 8lo then 8hi
The most efficient transmission used to be a direct drive top gear model, but now the best way is to have top gear as a single overdrive (approx 0:80 to one) with the next hole down being direct, with the correct drive axle gearing (approx 2:80 to one) the engine will be running on its sweet spot in direct gear when on the limiter, therefore suffering minimal mechanical losses from the gearing, yet still having that single overdrive for when the engine is not working hard, such as running with a good tail wind, or on nice flat ground or when lightly loaded, again Volvo have a version of I-Shift that does just this
newmercman:
Read my post again, for driving in normal conditions, I said the top of the green band, I.E. The top of the peak torque curve, never mentioned the top of the rpm rangeAnd please explain how shifting whole gears and not splitting every gear can be sequential
Sequential means using every gear one after the other, if you miss out a gear it’s a block change
The part about using the splitter on the way up the box only applies to hills, maybe I never made that clear enough
On the level, this is the recommended shift pattern in a 16spd transmission for a reasonably powered lorry at MGW :- 1lo, 2hi, 4lo, 5lo, 6lo, 7lo, 7hi, 8lo, 8hi. Pulling away in 1st is not strictly necessary, on some lorries that will be the crawler gear, but it’s very good for the clutch. If you don’t use 1st then 2lo to 4lo is the way to do it. On a downhill gradient or in a higher powered or lightly loaded lorry you could also miss out the split into 7hi and go 7lo to 8lo then 8hi
The most efficient transmission used to be a direct drive top gear model, but now the best way is to have top gear as a single overdrive (approx 0:80 to one) with the next hole down being direct, with the correct drive axle gearing (approx 2:80 to one) the engine will be running on its sweet spot in direct gear when on the limiter, therefore suffering minimal mechanical losses from the gearing, yet still having that single overdrive for when the engine is not working hard, such as running with a good tail wind, or on nice flat ground or when lightly loaded, again Volvo have a version of I-Shift that does just this
I think you’ve missed this part of the argument which is what I’m arguing about and skip shifting a lot of gears to the point of that situation and I just took it that you had no disagreement with that.
viewtopic.php?f=35&t=89371&start=300#p1284255
As for block changing I’m just associating it with the way I was taught it years ago during my first HGV 2 test and then again for my HGV 1 on the basis of gears to go brakes to slow and block changing was as I’ve said bring it all the way down to rest,or the speed you want take off again without any downshifts whatsoever and then just put it in the gear you want to take off in.Whereas,as I’ve said, dropping down the box whole gears or half gears at a time is effectively sequential downshifts compared to that idea. Which is why I did it that bs way to keep the instructor happy and then ‘sequentially’ just the way I’d been taught to drive a car by my Dad from day 1,and every other older driver to drive a truck at the time,for the tests and passed both first time. 
All of which seems to fit that video which I’ve posted many times of how they (rightly) expect it done over there by the book.
Going up the box and missing out a few half gears here and there is skip shifting not block changing at least the way I was taught the difference between the two.
So the question remains was ZB correct in his assumption concerning magazine road testers and manufacturers and if so is that the way that they’ve programmed an I shift to go up the box.
As for the idea of getting the thing up to peak power while it’s still on the flat before starting a climb I had that covered a while ago.
Carryfast:
It’s upshifting that we’re talking about not downshifting because it’s all about the best way to accelerate a truck up to speed.
That is effectively what they are doing. Afer all, if the 6 speed DB was good enough for a Gardner 180 at 30 tons, six gears is all you need to take a 400bhp 44 tonner from rest to 56mph.
Carryfast:
But going down the box whole gears at a time isn’t the same thing as block changes at all though that’s still effectively sequential downshifts but just missing some out on the way down.Block changing means missing out loads of gears to the point where it’s left the same one from like 50 mph all the way down to the speed and gear at which the wagon needs to pull away again having missed out every gear in between,on the basis of brakes to slow gears to go.The fact is you’re not going to be in ‘the green band’ by taking it up to peak ‘power’ at each upshift.Unless they’re putting the green band in the wrong place.
At or close to peak power. If is saves the fuel/time wasted during a gearchange, more revs is ok. It is not as if you are there for ever.
Carryfast:
But using a multi speed close ratio box by skipping gears on the way up,to the point where the engine is taken from the start of it’s torque band up to peak power,in each gear,just defeats the whole object of such boxes which are actually there to allow upshifts to be made over a narrow rev range much closer to the torque peak and well under the power peak just as I’ve said.
No, they are not. They are there to provide close ratios for hill-climbing, so the vehicle can operate as close as possible to the optimum engine speed on any hill, without being caught “between gears”.
Carryfast:
The former idea would just effectively turn a close ratio box back into a wide ratio one and waste loads of fuel and cause more wear and tear on the engine.Whereas lots of close ratio upshifts,especially using a constant mesh box,go through like lightning actually costing less momentum because the revs don’t need to fall as far during the gearchange,
I-shift uses the engine brake, automatically, to slow the engine between gears, so this argument holds no water.
Carryfast:
as they would from peak power back down into the torque band as was the case in the old days of wide ratio boxes.My question is are you actually saying that those engineers have actually programmed a modern close ratio multi speed constant mesh box to follow that idea of of taking the engine up to peak power at every upshift and block change it going down on that basis of gears to go brakes to slow
Does I-shift skip gears during braking? I would not be surprised- if it has control over the engine brake, what’s the problem?
[zb]
anorak:Carryfast:
It’s upshifting that we’re talking about not downshifting because it’s all about the best way to accelerate a truck up to speed.That is effectively what they are doing. Afer all, if the 6 speed DB was good enough for a Gardner 180 at 30 tons, six gears is all you need to take a 400bhp 44 tonner from rest to 56mph.
Carryfast:
But going down the box whole gears at a time isn’t the same thing as block changes at all though that’s still effectively sequential downshifts but just missing some out on the way down.Block changing means missing out loads of gears to the point where it’s left the same one from like 50 mph all the way down to the speed and gear at which the wagon needs to pull away again having missed out every gear in between,on the basis of brakes to slow gears to go.The fact is you’re not going to be in ‘the green band’ by taking it up to peak ‘power’ at each upshift.Unless they’re putting the green band in the wrong place.
At or close to peak power. If is saves the fuel/time wasted during a gearchange, more revs is ok. It is not as if you are there for ever.
Carryfast:
But using a multi speed close ratio box by skipping gears on the way up,to the point where the engine is taken from the start of it’s torque band up to peak power,in each gear,just defeats the whole object of such boxes which are actually there to allow upshifts to be made over a narrow rev range much closer to the torque peak and well under the power peak just as I’ve said.No, they are not. They are there to provide close ratios for hill-climbing, so the vehicle can operate as close as possible to the optimum engine speed on any hill, without being caught “between gears”.
Carryfast:
The former idea would just effectively turn a close ratio box back into a wide ratio one and waste loads of fuel and cause more wear and tear on the engine.Whereas lots of close ratio upshifts,especially using a constant mesh box,go through like lightning actually costing less momentum because the revs don’t need to fall as far during the gearchange,I-shift uses the engine brake, automatically, to slow the engine between gears, so this argument holds no water.
Carryfast:
as they would from peak power back down into the torque band as was the case in the old days of wide ratio boxes.My question is are you actually saying that those engineers have actually programmed a modern close ratio multi speed constant mesh box to follow that idea of of taking the engine up to peak power at every upshift and block change it going down on that basis of gears to go brakes to slow
Does I-shift skip gears during braking? I would not be surprised- if it has control over the engine brake, what’s the problem?
So now maybe we can find out wether nmm agrees with your assessment of what the manufacturers,magazine writers,and operators want from a driver compared to this video.There’s no way that what you’re saying is a description that matches what’s happening here.Which is a reasonable demonstration of what I’m describing as short shifted upshifts keeping the thing within it’s torque band without going anywhere near peak power.
youtube.com/watch?v=232B3Uakous
As for downshifting there’s only the right way or the wrong way and the right way means sequential,or as near sequential as makes no difference,double de clutched downshifts.
read my posts and you’ll see exactly how I think a lorry should be driven, block changing or skipshifting (tomayto-tamarto) is the way to do it
Up or down the box, makes no difference, the only time I would sequentially go up through the box would be going up a very big hill with a heavy load on from a dead stop
Coming down the box to slow down, I would be using the engine brake too, so I would be changing down a couple of gears to get the rpms up high and then coming down in full gears at least
On a big hill I would drop a full gear at 1100rpms, unless a single split would see me over the summit, once into a big climb it depends on a number of factors as to how I would change down, but my usual rule is down in whole gears and up in half gears
Are we clear now
Carryfast:
So now maybe we can find out wether nmm agrees with your assessment of what the manufacturers,magazine writers,and operators want from a driver compared to this video.There’s no way that what you’re saying is a description that matches what’s happening here.Which is a reasonable demonstration of what I’m describing as short shifted upshifts keeping the thing within it’s torque band without going anywhere near peak power.youtube.com/watch?v=232B3Uakous
As for downshifting there’s only the right way or the wrong way and the right way means sequential,or as near sequential as makes no difference,double de clutched downshifts.
The bloke in the first video changes up at 1500rpm and drops to about 1050rpm in the next gear. That’s about 30%- would it be reasonable to assume that he is not splitting every gear? Some engines, for example recent Cats, reach peak power at 1600rpm. He’s doing more or less what everyone on here has said- except you, cf!
the green in scania 1100 1700 ,it is more then a ful gear and you can easy take afull and ahalf not reving to peak power ,cheers benkku
[zb]
anorak:Carryfast:
So now maybe we can find out wether nmm agrees with your assessment of what the manufacturers,magazine writers,and operators want from a driver compared to this video.There’s no way that what you’re saying is a description that matches what’s happening here.Which is a reasonable demonstration of what I’m describing as short shifted upshifts keeping the thing within it’s torque band without going anywhere near peak power.youtube.com/watch?v=232B3Uakous
As for downshifting there’s only the right way or the wrong way and the right way means sequential,or as near sequential as makes no difference,double de clutched downshifts.
The bloke in the first video changes up at 1500rpm and drops to about 1050rpm in the next gear. That’s about 30%- would it be reasonable to assume that he is not splitting every gear? Some engines, for example recent Cats, reach peak power at 1600rpm. He’s doing more or less what everyone on here has said- except you, cf!
If you’d have read what I said I didn’t say split ‘every’ gear what I did say was that having more gears means closer ratios which allows them to shifted faster and allows the engine to be kept to a much more concentrated point closer to it’s torque peak.Even the most powerful recent euro truck options like the 730 Scania produce peak power at around 1800-2000 rpm.
What you said was along the lines of if a Gardner 180 powered wagon could make do with a 6 speed box then a 400 + one should be able to as well based on the (flawed) assumption that it’s best to upshift the thing at peak ‘power’ if I’ve read it right correct me if I’m wrong.
bma.finland:
the green in scania 1100 1700 ,it is more then a ful gear and you can easy take afull and ahalf not reving to peak power ,cheers benkku
So you’re saying that a Scania V8,like a 620 or a 730 will be more economical if you hang onto each gear up to at least 1,700 rpm,if not peak power, before upshifting it than upshifting it a long way below that figure .
As for me I wouldn’t mind doing some work for the wages and saving the guvnor some fuel so it would be kept between 1,100-1,350 or 1400 max unless it’s going to be climbing a mountain.That’s assuming that it could have a proper manual box like an 18 speed fuller put in it.
Here is an SFC(1/efficiency) graph I found, in the middle of someone’s emissions measurements. The report is here, if you are interested: vti.se/en/publications/pdf/s … st-346.pdf.
The tests were done on a Euro3 Scania 12 litre 420 engine.
Minimum full load SFC is 192g/kWh at 1200rpm. At full power, 1900rpm, SFC is 208g/kWh. In other words, the engine is only 8% less efficient with a full right boot on the red line, than it is plugging away at low revs. Then there is that 200g area up to 2100rpm. Bearing in mind V8lenny’s reading of the report into transient torque output, this suggests that it would be more efficient, in terms of fuel used versus journey time, to run the engine to 2100rpm, then select a gear to give 1000rpm and start again, than piddling about between 1000 and 1500rpm. Taking this to extremes, have a look at the results around 600rpm- less than 200g/kWh! If turbocharger lag is the main factor, using a wide spread of engine speed will give it more chance to reach its optimum steady-state conditions. Remember that time saved is fuel saved when accelerating, if you lower your cruising speed to give the same overall average speed.
V8lenny- if you could post a copy of the report on accelerating torque output, we may be able to compare this to the steady-state results on this graph, and estimate the best way to accelerate (in theory).
[zb]
anorak:
Here is an SFC(1/efficiency) graph I found, in the middle of someone’s emissions measurements. The report is here, if you are interested: vti.se/en/publications/pdf/s … st-346.pdf.
The tests were done on a Euro3 Scania 12 litre 420 engine.
0
1
The results are not typical, in that there is an extra low area at half load (1140rpm), in addition to the usual one at full load (1200rpm). Oddly enough, there is a nasty high point at 1700rpm full load, corresponding to a dip in maximum torque, at this point. Also, there is another low area at 2000-2100rpm- on this engine, there is good fuel economy to be had with the needle in the red! However, there is enough information in the graph to prove a point or two.Minimum full load SFC is 192g/kWh at 1200rpm. At full power, 1900rpm, SFC is 208g/kWh. In other words, the engine is only 8% less efficient with a full right boot on the red line, than it is plugging away at low revs. Then there is that 200g area up to 2100rpm. Bearing in mind V8lenny’s reading of the report into transient torque output, this suggests that it would be more efficient, in terms of fuel used versus journey time, to run the engine to 2100rpm, then select a gear to give 1000rpm and start again, than piddling about between 1000 and 1500rpm. Taking this to extremes, have a look at the results around 600rpm- less than 200g/kWh! If turbocharger lag is the main factor, using a wide spread of engine speed will give it more chance to reach its optimum steady-state conditions. Remember that time saved is fuel saved when accelerating, if you lower your cruising speed to give the same overall average speed.
V8lenny- if you could post a copy of the report on accelerating torque output, we may be able to compare this to the steady-state results on this graph, and estimate the best way to accelerate (in theory).
This sounds a bit like that ‘theory’ which says that a Gardner 150 powered 44 tonner would be ok on fuel consumption if you don’t mind having to wait until it gets to where it’s going.When in fact regradless of what the SFC figures might say on paper you’ve actually built a truck which does 6 mpg,at best,at an average speed of around 30 mph if you’re lucky and if there’s no hills in the way.
As for the bs about running an engine between 1,000 up to max power at each upshift maybe you’d like to try to sell that idea to any of the big fleets around the world,especially those running big power engine options,by telling them that everything they’ve heard so far about saving fuel and how to run a truck as fuel efficiently as possible has all been bs.
