I-shifts & other auto box attrocities

[carryfast]

V8Lenny:

Carryfast:
If I’ve read it right ZB’s theory is based on some SFC figures,rather than the old rules which as far as I know still apply,relating to use the torque not the power and keep it as close as possible to either side of the torque peak (in modern day engines obviously the centre of the plateau) regardless of how flat the torque curve is.That being most efficient method and certainly more efficient than running it up to peak power in every gear .

Sorry, old rules don’t apply, never have.

You don’t even seem to understand what are torque and power. There is no torque without power or power without torque. You never even get full torque at lower gears when driving your way because turbo never has enough time to reach maximum boost.

Power is just torque multiplied by engine speed and the turbo boost and the amount of lag is dependent on turbo size and vane geometry amongst loads of other (very) clever engineering which goes into getting a turbocharger to work from as low engine speed as possible with as little lag as possible.The specific torque output and the torque curve is a reasonable guide to the amount of boost the engine is getting.

[bma_finland]

gears or half gears ,that,s the cuestion manly a gear or 11/2gear up revs to 1500 or 1700 drop to 1000 or 950,in flat

[carryfast]

ramone:

kr79:

ramone:
After reading these confusing comments can someone tell me where im going wrong, i drive a CF Daf 460 double drive and the green band is between 1100rpm and 1500 rpm ,i normally set off in 2nd low ,then 4th low then 5th low ,once in top box i keep the revs between 1400rpm and 1200rpm with half gear up shifts and 1500rpm and 1100 rpm on full gear up shifts depending on the road and traffic conditions .I have the fuel consumption information on all the time , today i let it lug at 1100rpm where it struggled but kept pulling ,then i dropped half a gear and the revs went up to around 1350 rpm ,the fuel consumption also went up from 95 litres /100kms to 150 litres /100kms .The double drives are poor on fuel im averaging around 5.5mpg but we run at top weight on hilly terrain and the CF is low geared

That’s about right mate for one of them best motor I ever had on landfill work was a scania 124 420 used to average about 6mpg. Had a foden 4525 struggled to hit 5mpg.
Double drive will drop around 1mpg compared to a 6x2 before you take into account you will probaly be dragging a low loader or bulk rubbish trailer behind you. Then take in to account you are probaly going places where economical driving comes second to actualy keeping moving then pto use etc.

Im trying to understand reving engines up to 2000 rpm then change up 2 gears ,i would think it would do more harm than good im not a fan of screwing engines

The theory seems to be based on some flawed idea related to an overestimation of turbo lag,road speed losses during close ratio upshifts,and an underestimation of the amount that fuel consumption increases between peak torque and peak power and the extra time taken to upshift a box using a wider ratio gap that takes engine speed from peak power back down to around 1,000 rpm . .

[bma_finland]

and remember carryfast have don a great carrier on flat,s AIRPORTS,and couse of the V16 dd and 18speed fuller,we al have made many safe flight,s round the world,but don,t think he have been on road latly,exept whit the jaguar

[ramone]

Carryfast:

ramone:

kr79:

ramone:
After reading these confusing comments can someone tell me where im going wrong, i drive a CF Daf 460 double drive and the green band is between 1100rpm and 1500 rpm ,i normally set off in 2nd low ,then 4th low then 5th low ,once in top box i keep the revs between 1400rpm and 1200rpm with half gear up shifts and 1500rpm and 1100 rpm on full gear up shifts depending on the road and traffic conditions .I have the fuel consumption information on all the time , today i let it lug at 1100rpm where it struggled but kept pulling ,then i dropped half a gear and the revs went up to around 1350 rpm ,the fuel consumption also went up from 95 litres /100kms to 150 litres /100kms .The double drives are poor on fuel im averaging around 5.5mpg but we run at top weight on hilly terrain and the CF is low geared

That’s about right mate for one of them best motor I ever had on landfill work was a scania 124 420 used to average about 6mpg. Had a foden 4525 struggled to hit 5mpg.
Double drive will drop around 1mpg compared to a 6x2 before you take into account you will probaly be dragging a low loader or bulk rubbish trailer behind you. Then take in to account you are probaly going places where economical driving comes second to actualy keeping moving then pto use etc.

Im trying to understand reving engines up to 2000 rpm then change up 2 gears ,i would think it would do more harm than good im not a fan of screwing engines

The theory seems to be based on some flawed idea related to an overestimation of turbo lag,road speed losses during close ratio upshifts,and an underestimation of the amount that fuel consumption increases between peak torque and peak power and the extra time taken to upshift a box using a wider ratio gap that takes engine speed from peak power back down to around 1,000 rpm . .

Someone will probably shout me down but i thought over reving engines just wasted fuel and over stressed the engine ,whats the point of the green band then?

[carryfast]

ramone:

Carryfast:

ramone:

kr79:

ramone:
After reading these confusing comments can someone tell me where im going wrong, i drive a CF Daf 460 double drive and the green band is between 1100rpm and 1500 rpm ,i normally set off in 2nd low ,then 4th low then 5th low ,once in top box i keep the revs between 1400rpm and 1200rpm with half gear up shifts and 1500rpm and 1100 rpm on full gear up shifts depending on the road and traffic conditions .I have the fuel consumption information on all the time , today i let it lug at 1100rpm where it struggled but kept pulling ,then i dropped half a gear and the revs went up to around 1350 rpm ,the fuel consumption also went up from 95 litres /100kms to 150 litres /100kms .The double drives are poor on fuel im averaging around 5.5mpg but we run at top weight on hilly terrain and the CF is low geared

That’s about right mate for one of them best motor I ever had on landfill work was a scania 124 420 used to average about 6mpg. Had a foden 4525 struggled to hit 5mpg.
Double drive will drop around 1mpg compared to a 6x2 before you take into account you will probaly be dragging a low loader or bulk rubbish trailer behind you. Then take in to account you are probaly going places where economical driving comes second to actualy keeping moving then pto use etc.

Im trying to understand reving engines up to 2000 rpm then change up 2 gears ,i would think it would do more harm than good im not a fan of screwing engines

The theory seems to be based on some flawed idea related to an overestimation of turbo lag,road speed losses during close ratio upshifts,and an underestimation of the amount that fuel consumption increases between peak torque and peak power and the extra time taken to upshift a box using a wider ratio gap that takes engine speed from peak power back down to around 1,000 rpm . .

Someone will probably shout me down but i thought over reving engines just wasted fuel and over stressed the engine ,whats the point of the green band then?

^ This.Although there are circumstances where running up to near peak power like hill climbing etc is needed.It’s only really over revving to run an engine beyond peak power which is usually marked yellow before that then red after.

[zb_anorak]

Bassman:
Ooop’s foot in it again, common fault with me!

Cheers Bassman

No problem Mr. Bass. My foot’s in it so often, I wear wellies in the house.

[tony_taylor]

[zb]
anorak:

kr79:
Tony Taylor- how can you not like this? It’s better than Match of the Day! Well done kr79, for brightening up the forum, and beating the computer 8.79 to 8.38. Three points to you!

Hi,I didn’t say that I don’t like it,I just think the technicalities may be over the heads of some of the members whose grasp of the scientifics involved is not as good some of the learned posters.(me included) I don’t mean that in a patronising way!! but it’s a fact.As for being better than match of the day,it depends who is playing.If you ask any of the older drivers,I am willing to bet that most of them never looked at the rev counter when they were changing gear,they,(we), just knew when to change gear going up hill or down.The same road is different every time you drive it,every hill is different each time you climb it or descend it,depending on the weight of the load and the conditions at the time.Experience and skill tells a good driver what to do and he can adapt to any road conditions.I do admit that some of the skill has been taken out of the job with the introduction of the mod cons,and I do admire kr79 for showing the different ways of driving the I shift with the resulting MPG.It just goes to show that the driver can still influence the performance of the truck despite the attempts of the boffins to take it out of our hands.

[zb_anorak]

V8Lenny:
I have 850 hp and I drive it flat to the floor, from 1200 to 2100 rpm, like every good driver does, and I get 8.3 mpg. 16 years old truck, base engine from -69, manual gears (12+2).

Like I said earlier, it has been proved many times, on the dyno and on the road, so it works, before, now and in the future.

100%

[carryfast]

[zb]
anorak:

V8Lenny:
I have 850 hp and I drive it flat to the floor, from 1200 to 2100 rpm, like every good driver does, and I get 8.3 mpg. 16 years old truck, base engine from -69, manual gears (12+2).

Like I said earlier, it has been proved many times, on the dyno and on the road, so it works, before, now and in the future.

100%

So you’re saying if you drive a 730 Scania loaded to 44 t gross everywhere using that method then it’ll return better than 8.3 mpg .

[newmercman]

I think that the different perspectives on this thread have got something for everyone, from the scientific to the simple, there’s a lot of good information here and throughout my driving career good information has always been useful, most of the stuff I talk about on here has been learned from listening to good information, I wasn’t born with any of it pre programmed into my brain, I’ve learned it all from either doing it or listening to someone who has done it, all things considered, even though I’ve done quite a lot, I’ve learned a hell of a lot more by listening and reading than from anything else

So, with that in mind, Carryfast, in a vain effort to possibly educate you, I would like to draw to your attention the phrase There’s more than one way to skin a Cat

In respect of driving a lorry that phrase sums it up

The way you describe going through the gears is similar to a CVT (Continuosly Variable Transmission) so that you keep the engine on the boil all the time, I don’t think that it’s necessary and it makes life a lot more difficult than it needs to be, but there are worse things you could do, especially in the operation that you were in with light loads, night time traffic volumes and motorway along the majority of the route. If you were to drive your lorry in that way all the time, your fuel returns would more than likely be up in the top 10% in the average fleet

However, there would be 90% below you and that 90% are the type of driver (steering wheel attendant) that the designers of Auto Shifts had in their sights The drivers that go right up to the red line and then split each gear so they spend the whole day revving the nuts off the engine, or the drivers that can’t be bothered to drop a cog or two and labour the engine (which is just about the worst thing you can do to an engine) or the drivers that cannot master a constant mesh transmission, there are plenty of them out there, I’m pretty adept at jamming gears, but I sometimes curse the evil that is a Fuller box at times The Auto Shift takes the lowest common denominator drivers and improves their mpg and mechanical sympathy by a huge amount, purely by removing their need to actually drive the lorry

As Kevin has demonstrated, a good driver can better the figures achieved by auto shifts, even the Volvo I-Shift, which deservedly sets the standard for all AMTs, but we go back to the beginning again, the good driver doesn’t need help, it’s the 90% below them that do, they’re the reason we’re lumbered with all this gadgetry that takes away our need to be lorry drivers

[paul_john]

Nicely put Mark.

[bassman]

Hi, NMM,
As Paul john say’s nicely put. I agree with C/F about keeping an engine “on the boil” or “in the sweet spot” or whatever term is used. In day’s of yore that was the way to do it because you didn’t have the power. You needed multi geared boxes to get anywhere , you had to consider which road you took in case there was a hill on it you would struggle on.
Imagine, a 240 8LXB Gardner with a 18 speed fuller at the back! you’d be unstoppable!
Today’s engines , however,are generally more powerful ,more forgiving, so don’t require to be taken to the limit in each gear, as Tony Taylor said , you drive ,a lot of the time, with your ears, you change gear when it sounds right. There are exceptions ,when you want to be prepared for what is in front( I-Shift, hill coming up manual possibly?) that you treat the norm. differently
Personally , I don’t want to go down the road watching the rev counter all the time, waiting for that extra two hundred revs before I change up, when under most conditions it won’t matter if I’m four or five hundred revs short because the engine will take it. And if it’s an auto the wizardry will sort that out for me, if I’m having an off day or I’m not to involved in the exact science of getting a truck from A to B.
There is enough out there for me to worry about without knowing all the mathematics, let’s enjoy what we can.

Cheers Bassman

[v8lenny]

Carryfast:
Power is just torque multiplied by engine speed and the turbo boost and the amount of lag is dependent on turbo size and vane geometry amongst loads of other (very) clever engineering which goes into getting a turbocharger to work from as low engine speed as possible with as little lag as possible.The specific torque output and the torque curve is a reasonable guide to the amount of boost the engine is getting.

Yes, take a FH12 Volvo and start accelerating through all the gears at about 40 tons. What gear you are at before you get full boost? What gear are you at when you have full boost for more than 1 second?

Max boost means max torque means max fuel efficiency. If you are driving light pedal low boost short burst at every gear you never get max fuel efficiency out of the engine. SFC is always measured at max load, part load SFC is very bad. SFC is even worse at transients, meaning at every gearchange when you are trying to recover the boost.

[v8lenny]

newmercman:
The way you describe going through the gears is similar to a CVT (Continuosly Variable Transmission) so that you keep the engine on the boil all the time.

Difference is CVT and Allisons (real automatics) don’t loose boost when they shift, Carryfasts theory works with those transmissions but not with manuals and automated manuals. Might also work with non-turbo engines like MB and Detroit.

[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.

[kr79]

Obviously 1900 rpm in this truck other trucks with different engines and gearing may have different characteristics.

[v8lenny]

kr79:
Obviously 1900 rpm in this truck other trucks with different engines and gearing may have different characteristics.

Volvos start to loose power quite rapidly after 1700 rpm so there’s not much use to rev much higher, 1800-1900 is a good shift point in low range, in high range 1700-1800. When you get used to it you don’t have to watch the rev counter all the time.

[ramone]

So why do manufacturers put the green band there in the first place,i thought it was for fuel efficient driving,i dont know if anyone else has driven 1 but we had several R420 opticruise Scanias with overdrive top which gave 90 kms at 1100 rpm barely in the green but gave the impression the engine was labouring all the time excellent on fuel though on our light work at that time

[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.