kr79:
Obviously the lower the revs the less fuel the engine uses
^^ This.That’s what I’ve been saying although there is a point where those revs can be too low just a there is a point where they can be too high.Too high meaning in most cases much beyond peak torque.As for V8 Lenny’s ideas of running it up to peak power in every gear using less of them or nmm’s idea that using plenty of gears only applies in the case of running at light weights,if the idea of using less gears and running it up to peak power running at high weights was more economic on fuel that’s what this driver would be doing instead of the opposite.
One of the main reasons why big power,decent engined trucks,never took off over here like in the States and the colonies is because too many Brits seem to have the old Gardner way of driving,with a wide ratio box,and where it needed to be taken up to peak power in every gear because it had no torque,programmed into their DNA.
kr79:
Obviously the lower the revs the less fuel the engine uses so running on the motorway having a deep overdrive helps but you need to change down as soon as you hit a hill. Lots of drivers didn’t realise this was the case and just thought the lorrys were gutless as you had to drop a gear where other trucks with a direct top gear would take the hill in top but would be loosing revs from over the top of where the torque is.
We were running very light 23 tons gross so on trunking never out of top on motorways they were returning 11.5 mpg after we had the kick down turned off
I was referring to when it is cruising not getting to speed. As for the video it’s missing the point as that thing weighs nearly double what a fully freighted uk artic weighs.
I don’t know if you have driven anything super heavy I’ve been up to 65 ton so nothing major but even that is very different than 44 ton.
kr79:
I was referring to when it is cruising not getting to speed. As for the video it’s missing the point as that thing weighs nearly double what a fully freighted uk artic weighs.
I don’t know if you have driven anything super heavy I’ve been up to 65 ton so nothing major but even that is very different than 44 ton.
I think you’ve missed nmm’s point and if V8 Lenny is right then using less gears and running the thing up to peak power in every gear while accelerating up to speed is how that Oz driver would be driving that CAT.But the inconvenient truth is that he isn’t because it costs fuel and it knackers engines regardless of wether it’s running at 30 t gross,40 t gross,or 80 t gross.
kr79:
I was referring to when it is cruising not getting to speed. As for the video it’s missing the point as that thing weighs nearly double what a fully freighted uk artic weighs.
I don’t know if you have driven anything super heavy I’ve been up to 65 ton so nothing major but even that is very different than 44 ton.
I think you’ve missed nmm’s point and if V8 Lenny is right then using less gears and running the thing up to peak power in every gear while accelerating up to speed is how that Oz driver would be driving that CAT.But the inconvenient truth is that he isn’t because it costs fuel and it knackers engines regardless of wether it’s running at 30 t gross,40 t gross,or 80 t gross.
Seems like Aussies don’t know any better than US drivers. If it was a cold engine then that’s the way to do it, no boost over 1 bar before the engine gets up to temp. And it was an ancient V8 Cat that was not known to be very powerful and didn’t have very wide torque curve.
This driving style I’m referring to is not my idea, every economy driving instructor will tell you the same, no matter if it’s truck or car you are driving.
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
kr79:
I was referring to when it is cruising not getting to speed. As for the video it’s missing the point as that thing weighs nearly double what a fully freighted uk artic weighs.
I don’t know if you have driven anything super heavy I’ve been up to 65 ton so nothing major but even that is very different than 44 ton.
I think you’ve missed nmm’s point and if V8 Lenny is right then using less gears and running the thing up to peak power in every gear while accelerating up to speed is how that Oz driver would be driving that CAT.But the inconvenient truth is that he isn’t because it costs fuel and it knackers engines regardless of wether it’s running at 30 t gross,40 t gross,or 80 t gross.
Seems like Aussies don’t know any better than US drivers. If it was a cold engine then that’s the way to do it, no boost over 1 bar before the engine gets up to temp. And it was an ancient V8 Cat that was not known to be very powerful and didn’t have very wide torque curve.
This driving style I’m referring to is not my idea, every economy driving instructor will tell you the same, no matter if it’s truck or car you are driving.
I think you’ll find that 3408 is likely to be putting out a few more horsepower than the standard ratings used for it’s typical 1970’s US 36 tonner application.Just read the comments below it which should provide some idea of the type of outputs they use.
If any economy driving instructor tells anyone to run a truck up to peak power in every gear to reduce the amount of gears used to accelerate a loaded truck up to speed it’s going to be anything but economical.
kr79:
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
According to the (erroneous) theory using more gears costs more in speed lost to gear changes than using less gears so if you’re right that would actually magnify that situation not reduce it.
As nmm correctly said the ideal is the continuously variable transmission and that’s what having a multi speed box is all about.His mistake was in thinking that ideal only applies in the case of relatively light weights when it applies regardless of weights.Which then just leaves the question of the most economical rev range where that (as close as it gets to a) CVT needs to operate at and anywhere near peak power ain’t it.
kr79:
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
I’m from Finland, do you think I have never driven anything heavy? Legal is 60 tons but there’s not much control…
Carryfast:
If any economy driving instructor tells anyone to run a truck up to peak power in every gear to reduce the amount of gears used to accelerate a loaded truck up to speed it’s going to be anything but economical.
kr79:
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
According to the (erroneous) theory using more gears costs more in speed lost to gear changes than using less gears so if you’re right that would actually magnify that situation not reduce it.
As nmm correctly said the ideal is the continuously variable transmission and that’s what having a multi speed box is all about.His mistake was in thinking that ideal only applies in the case of relatively light weights when it applies regardless of weights.Which then just leaves the question of the most economical rev range where that (as close as it gets to a) CVT needs to operate at and anywhere near peak power ain’t it.
No but you can keep the power on before road speed drops to much.
kr79:
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
I’m from Finland, do you think I have never driven anything heavy? Legal is 60 tons but there’s not much control…
I was talking to carryfast I was just going from my limited experince of driving my firms low loader at 65 ton a Volvo fh and that doesn’t respond to big gearchanges at full weight.
kr79:
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
According to the (erroneous) theory using more gears costs more in speed lost to gear changes than using less gears so if you’re right that would actually magnify that situation not reduce it.
As nmm correctly said the ideal is the continuously variable transmission and that’s what having a multi speed box is all about.His mistake was in thinking that ideal only applies in the case of relatively light weights when it applies regardless of weights.Which then just leaves the question of the most economical rev range where that (as close as it gets to a) CVT needs to operate at and anywhere near peak power ain’t it.
No but you can keep the power on before road speed drops to much.
Either using more gears but closer gears costs more time and road speed lost to gear shifts than using less gears but wider gears or it doesn’t so which is it . But adding more weight and drag isn’t going to make that situation any better ‘if’ the (erroneous) theory of using less gears costs less time and road speed lost to gear shifts while using more but closer ones does cost more,is correct.
Here’s a clue even at the old 8 wheeler rigid type weights it wasn’t unheard of (in fact it was quite common) for a truck to run out of road speed completely and come to a halt before it could be upshifted into the next gear up because of the excessively wide ratio boxes of the time.I’ve never heard of the same problem happening to US trucks at least those fiited with the early forms of multi speed transmissions let alone 13 and 18 speed fullers with a weight limit of less than 38 t gross.
kr79:
If you had ever driven anything heavy rather than watched you tube videos you would know the weight and drag from the amount of axles something heavy has as soon as you dip the clutch the thing will slow rapidly so if you change up two or three gears at a time the thing will have slowed two Mutch for that gear. So going up the gears one at a time is the order of the day a 40 or 44 ton truck and 450 or so hp is very different.
According to the (erroneous) theory using more gears costs more in speed lost to gear changes than using less gears so if you’re right that would actually magnify that situation not reduce it.
As nmm correctly said the ideal is the continuously variable transmission and that’s what having a multi speed box is all about.His mistake was in thinking that ideal only applies in the case of relatively light weights when it applies regardless of weights.Which then just leaves the question of the most economical rev range where that (as close as it gets to a) CVT needs to operate at and anywhere near peak power ain’t it.
No but you can keep the power on before road speed drops to much.
You’ve already said that using less wider gears in the most extreme situations of weight and/or drag costs more time and road speed lost to upshifting than using more but closer gears.The fact is nothing changes regarding that situation wether it’s a 30 tonner or an 80 tonner.
kr79:
Right today tried from a standing start to the limiter in power mode 53.2 seconds.
Tried 0 to limiter in manual max revs changing up as many gears as possible 46.1 seconds
Also same in economy mode 59.8 seconds.
Although you do go up three gears at a time you don’t realy as you have to press the button three times and the first push gives you a gear as you don’t need to lift of the throttle.
IMHO going over 1900rpm isn’t realy worth it for the long term life of the engine and the fact is we are drivin lorrys not drag racing.
Today in power mode when it hit 9th it went up one gear at a time as I was on a slight climb I suppouse. The same as I would have done in a manual.
The fact is with a modern truck with the power they have 12 gears are quite enough a 16 or 18 speed is just a waste of money and weight.
The same as Tony Taylor I’ve think of my self as just a driver I had never heard of sfc and some of the other stuff on here until recently. It has been interesting and I have learned a few things but I don’t think I’ve looked at a rev counter as much in the last 5 years as I have the last few days. I’ve always driven by my eyed and ears and don’t profess to be any kind of advanced elite driver but it proves there’s no hard and fast rule of how to operate the truck it’s knowing what’s best at that time.
More interesting stuff from our chief test driver!
The acceleration tests surprised me, given that the I-shift is noted for a quick change: the improvement in acceleration, by reducing the number of changes, compared to Performance mode, was quite marked.
I can understand your reluctance to “thrash” the engine. Even if the lorry belongs to someone else, no one with any sense would want to wreck another man’s property. Looking at the I-shift spec sheet again, it appears that, by changing up three gears at 1950rpm, you get about 950rpm in the next gear. This may be a good compromise, giving you some of the improved acceleration (and maybe a small fuel saving).
What a shame the I-shift (in Manual) takes the first button-press as an instruction to change one gear. You would hope to be able to select a three-gear up- (or down-) change, decisively. If it had three buttons, one for a single gearchange, two for two and so on, the skip shifts may be even quicker. If anything, there would be less wear on the linkage and selector forks etc, one would think.
Once again, kr79, thanks for your work. You have certainly given this old git food for thought, if nothing else!
Real life experince here in my firms fh 460 at 65 ton I used 1 lo 2 hi 3 hi 4 lo 4hi 5 lo 5hi 6 lo 6 hi as I felt due to the road conditions at that weight that was the best way to progress without losing momentum or leaving the prop on the floor the fact remains you don’t need 18 gears at 44 ton but they will be useful at higher weights but just because they are there it doesn’t meant you will have to use them. 460 is modest power at 65 ton so it will be useful to have a few gears same as in past times a 2 speed axle would help or fodens 12 speed box could help a lower power engine.
Carryfast:
If any economy driving instructor tells anyone to run a truck up to peak power in every gear to reduce the amount of gears used to accelerate a loaded truck up to speed it’s going to be anything but economical.
OK, I’ve had enough of you, again. Good bye!
Please don’t leave the forum, on account of one man’s intransigence. Your assertion, “I have 850bhp and I drive it foot to the floor, like every good driver should,” is my all-time favourite TNUK quote. We want more of this good stuff! Your work on engine modifications is particularly interesting. To get the extra power, does it involve advancing the injection timing? What effect has it had on peak cylinder pressures?
[zb]
anorak:
Looking at the I-shift spec sheet again, it appears that, by changing up three gears at 1950rpm, you get about 950rpm in the next gear. This may be a good compromise, giving you some of the improved acceleration (and maybe a small fuel saving)
Maybe if it’s just a unit running solo and you’re in a hurry to get somewhere to collect a loaded trailer.
Obviously my tests were not under struck truck mag test type situations but I’m guessing Volvo and the others build a bit of slack in to the program to stop abuse and the auto wouldnt wring every last bit out of the engine all day every day.
Sadly I don’t claim to be a lorry driving guru like our gritter driver so couldn’t confirm this.
As you say it would be a shame if v8 stoped posting as he has had some interesting contributions although the more of carryfasts drivel I read I begin to think he has never driven a lorry in his life.
