Don’t need to bury your foot in the floor 1500 1600 rpm is enough before shifting up generally speaking my Volvo with I shift goes 3 5 7 9 11 12 at 32 ton with 380 bhp. That changed up at 1600 rpm
kr79:
Don’t need to bury your foot in the floor 1500 1600 rpm is enough before shifting up generally speaking my Volvo with I shift goes 3 5 7 9 11 12 at 32 ton with 380 bhp. That changed up at 1600 rpm
Hi kr79. Bearing in mind that:
- Engines are usually more efficient at full load, throughout the speed range.
- Steady-state running is more efficient than accelerating.
I would guess that a buried foot is best. Get the acceleration done in as short a distance as you can. What does your I-shift do, if you floor it? Is there an “economy” or “performance” button that you can select? I would be interested to see what the manufacturers have programmed into it. Of course, much of their motivation is to eliminate driver abuse, so this may thwart the efforts of the conscientious driver in some cases.
carryfast talks more teory then the teoretical skedules even 
,come on back to the road,cheers benkku
bma.finland:
carryfast talks more teory then the teoretical skedules even
Hej hej. It’s all theory, until someone on the forum decides to put an accurate fuel flowmeter on his lorry and perform a series of acceleration tests, measuring time and distance as well as fuel use. Cf does not understand the theory- that is the difference. I put a perfectly good graph in front of him, showing the measurements recorded by real engineers on a real engine. His conclusion: “bs”.
[zb]
anorak:kr79:
Don’t need to bury your foot in the floor 1500 1600 rpm is enough before shifting up generally speaking my Volvo with I shift goes 3 5 7 9 11 12 at 32 ton with 380 bhp. That changed up at 1600 rpmHi kr79. Bearing in mind that:
- Engines are usually more efficient at full load, throughout the speed range.
- Steady-state running is more efficient than accelerating.
I would guess that a buried foot is best. Get the acceleration done in as short a distance as you can. What does your I-shift do, if you floor it? Is there an “economy” or “performance” button that you can select? I would be interested to see what the manufacturers have programmed into it. Of course, much of their motivation is to eliminate driver abuse, so this may thwart the efforts of the conscientious driver in some cases.
Here’s another grenade to throw into your theory and nmm probably won’t like it either.The main parameters that the fuel system uses to determine how much fuel the engine gets is load and engine speed.If you can cut either of those you’ll save some fuel if you can cut both you’ll save lots of fuel.That’s why a engine burns more fuel to run at high speeds because the engine needs to turn over faster while the air resistance adds to the load.It’s also why an engine burns less fuel when it’s hauling a lighter weight.The only real control which you’ve got over those issues is to either run lighter,run slower,or cut engine speed using more torque to pull higher gearing. 
While in the real world the fact is the more right foot you give it the more fuel it’ll burn and the higher the speed that the engine turns over while it’s doing that then the more fuel it’ll burn on top of that.
[zb]
anorak:bma.finland:
carryfast talks more teory then the teoretical skedules evenHej hej. It’s all theory, until someone on the forum decides to put an accurate fuel flowmeter on his lorry and perform a series of acceleration tests, measuring time and distance as well as fuel use. Cf does not understand the theory- that is the difference. I put a perfectly good graph in front of him, showing the measurements recorded by real engineers on a real engine. His conclusion: “bs”.
The conclusion of bs is based on the fact that the theory is based on just one specific parameter (SFC) which really tells you nothing about how much fuel gets burnt in the real world and why.
If I’m wrong then maybe you can answer the question as to why running at higher speeds requires more fuel assuming that you’re correct in your assumptions because if basing the fuel requirement on your theory is correct that fuel consumption would improve the faster the thing goes. 
Carryfast:
[zb]
anorak:bma.finland:
carryfast talks more teory then the teoretical skedules evenHej hej. It’s all theory, until someone on the forum decides to put an accurate fuel flowmeter on his lorry and perform a series of acceleration tests, measuring time and distance as well as fuel use. Cf does not understand the theory- that is the difference. I put a perfectly good graph in front of him, showing the measurements recorded by real engineers on a real engine. His conclusion: “bs”.
The conclusion of bs is based on the fact that the theory is based on just one specific parameter (SFC) which really tells you nothing about how much fuel gets burnt in the real world and why.
If I’m wrong then maybe you can answer the question as to why running at higher speeds requires more fuel assuming that you’re correct in your assumptions because if basing the fuel requirement on your theory is correct that fuel consumption would improve the faster the thing goes.
We are not talking about driving faster but accelerating up to cruising speed. You don’t seem to get it. I could scan the tests from the book I mentioned earlier but you wouldn’t understand because it’s in finnish. There must be similar tests made in other countries also.
V8Lenny:
Carryfast:
[zb]
anorak:bma.finland:
carryfast talks more teory then the teoretical skedules evenHej hej. It’s all theory, until someone on the forum decides to put an accurate fuel flowmeter on his lorry and perform a series of acceleration tests, measuring time and distance as well as fuel use. Cf does not understand the theory- that is the difference. I put a perfectly good graph in front of him, showing the measurements recorded by real engineers on a real engine. His conclusion: “bs”.
The conclusion of bs is based on the fact that the theory is based on just one specific parameter (SFC) which really tells you nothing about how much fuel gets burnt in the real world and why.
If I’m wrong then maybe you can answer the question as to why running at higher speeds requires more fuel assuming that you’re correct in your assumptions because if basing the fuel requirement on your theory is correct that fuel consumption would improve the faster the thing goes.
We are not talking about driving faster but accelerating up to cruising speed. You don’t seem to get it. I could scan the tests from the book I mentioned earlier but you wouldn’t understand because it’s in finnish. There must be similar tests made in other countries also.
The fuel requirement under acceleration is still based on those same parameters of load and engine speed.The heavier the truck and/or the faster it accelerates the more fuel it’ll need to do it.The only way of mitigating that issue is to use more torque,to pull higher gearing, which has the effect of reducing engine speed while still turning the wheels at a decent speed.However there’s no point in the designers going to all the trouble of doing that when there’s a theory out there which says run an engine,up to peak power,in every gear, 
on the flawed assumption that it will save fuel doing it.
Nothing scientific but I’ve been on the same job all afternoon using the p mode it chose the same gears but ran the revs up to 1900 before changing. Slightly quicker to 50 than economy mode. Tried changing manually using all gears at about 1300 rpm. Remember I shift is lightning fast quicker than any driver on a fuller and won’t miss a cog and all I did was make noise and not a lot of progress I was doing just over 30 where I was doing 50 driving normaly.
I have a feeling carryfasts way is how a diesel engine works on paper and would be fine in a peice of static machinery or a boat but in real life on the road where lots of other factors come in to play its not quite the same.
interesting that a man who wanted even more and more horsepowers thursty ones,now speaks for fueleconomy you can save fuel whit a 420 motor for thouse who needs al gears, whit a bigger engine AND BRAIN you save as mutch cheers benkku
V8Lenny:
We are not talking about driving faster but accelerating up to cruising speed. You don’t seem to get it. I could scan the tests from the book I mentioned earlier but you wouldn’t understand because it’s in finnish. There must be similar tests made in other countries also.
You’re right Lenny. He does not understand, so as soon as it gets harder than schoolgirl maths, the connection between the theory and practice is lost, replaced with waffle.
I would like to see the tests from the book. I can read Finnish numbers, at least!
we are talking about DRIVING on road and town 
,in al condisions and different loading
Carryfast it’s simple to understand No really it is
Now, go back and look at the SFC graph posted by [ZB] who does get it 
From 1050-1500 rpms the torque is high and the fuel consumption is good, that gives you a 450rpm window, which will allow a full gear shift, so shortshifting will achieve nothing except one thing…
It will use more fuel
If you draw a graph to show the time taken for a lorry to reach cruising speed from rest it will not be a linear line, but will have a saw tooth effect, this will come from changing gear, the lorry stops gaining forward motion and slows down. Are you with me so far
Put simply you will lose 3mph of speed for each gearchange, this speed has to be recovered in order to reach cruising speed, the way a lorry does this is by using more fuel and taking more time
If you change gear 8 times on the way up to speed by using full gearshifts you lose 24mph which must be recovered to reach cruising speed
If you change gear 16 times on the way up to speed by using splitshifts you lose 48mph which must be recovered to reach cruising speed
So, in your infinite wisdom, please tell me how throwing 48mph away is going to be more efficient
I don’t think even the most dedicated driver who is driving for a company knows, or even wants to know about torque curves, Newton meters, gearbox ratios etc. etc.He will do his (or her) best to do the job to the best of his ability and that will include getting the best out of the truck.The typical good driver is just that-- a GOOD driver,he is not a technician or a design engineer,he just wants the truck to IT’S job as well as he does his,whether he’s driving with a manual or an automated gearbox.I think getting too technical is probably stopping some of the other members from posting their views on “I- shifts & other auto box attrocities” It’s just my opinion. 
Just found this, those engineers at Detroit/Freightliner must be stupid. Or what do you think CF ?
Advanced technologies include Skip Shift, which automatically skips gears, enabling the transmission to run through lower gears faster to achieve cruising speed sooner; and eCoast, which allows the vehicle to ‘coast’ down grades with the engine operating at idle speeds while preserving vehicle momentum, maximizing fuel efficiency.
Auto boxes, I shifts etc. were bought in to eliminate the style of driving Carryfast advocates. 
The I shift doesn’t need every gear in the box all the while, just as a sensible driver wouldn’t need them all the while in a manual box.
Modern trucks with a fuel computer backs this up.
Tony Taylor:
I don’t think even the most dedicated driver who is driving for a company knows, or even wants to know about torque curves, Newton meters, gearbox ratios etc. etc.He will do his (or her) best to do the job to the best of his ability and that will include getting the best out of the truck.The typical good driver is just that-- a GOOD driver,he is not a technician or a design engineer,he just wants the truck to IT’S job as well as he does his,whether he’s driving with a manual or an automated gearbox.I think getting too technical is probably stopping some of the other members from posting their views on “I- shifts & other auto box attrocities” It’s just my opinion.
You may have a point there Tony, I understand the basics of all that techno stuff, but I must admit it took some concentration for me to digest it all 
However, the authors of those posts do know what they’re talking about, it may go over the heads of most, but the information is still on topic and relevant, which is more than can be said of some posts
If that sort of thing doesn’t interest anybody, it’s quite easy to skip through it and not lose the momentum of the thread, you can also skip through any of the other posts and ignore what is written, but then with all the wonderful contributions we’ve had so far, I can’t see that it would apply here
kr79:
Nothing scientific but I’ve been on the same job all afternoon using the p mode it chose the same gears but ran the revs up to 1900 before changing. Slightly quicker to 50 than economy mode. Tried changing manually using all gears at about 1300 rpm. Remember I shift is lightning fast quicker than any driver on a fuller and won’t miss a cog and all I did was make noise and not a lot of progress I was doing just over 30 where I was doing 50 driving normaly.
I have a feeling carryfasts way is how a diesel engine works on paper and would be fine in a peice of static machinery or a boat but in real life on the road where lots of other factors come in to play its not quite the same.
This is superb stuff, kr! One minute we’re arguing the theory, the next we have the results of a practical set of tests. Brilliant!Any chance of measuring fuel consumption and journey time (for the same route, ideally, but any information is good)?
I assume, when using Economy mode, you are accelerating with the accelerator fully depressed?
I would be interested to see what happens if, when accelerating from rest (or a low speed), using Manual, you take it to 1900rpm, then change into the highest gear you would consider using- say, the one that gives around 900-1000rpm. In other words, accelerating using full “throttle” (they don’t have throttles, but what do you say? Full rack? Full pump? Full welly? ), but using the minimum number of gearchanges you can get away with.
I always to set off loaded in first and use the gears I considered appropriate to the road conditions and I always recorded decent fuel figures, I did enter a Volvo contest at Cranfield when the F10 came out and I came second ( I won £100-00 ) which was a metered fuel economy drive and an O/D from the Shropshire area won a Volvo 343 car and that was the first time I had ever been in a F10 never mind drive one and skip shifted.
cheers Johnnie
P S I had to use every gear when driving a Scammell gate change
Ten days in my company and some of my brilliance has rubbed off on you then Kev Next you’ll be talking about tyres and rear axle ratios
As [zb] says, excellent stuff, although it won’t stop the madness coming from the Leatherhead Branch of the Wheeltapper’s and Shunter’s Club
I haven’t done any testing from a dead stop for years, the block shifting method is the one I’ve always used and as it is the correct way there’s no need to try anything else. I have tried progressive shifting the North American way, but an almost complete lack of forward motion put a stop to that
In my mind, using the best part of the torque curve and minimising gearshifts to get to cruising speed as quickly as possible is the way to do it properly, you cannot really save a significant amount of fuel during acceleration, so get up to speed as fast as possible and concentrate on saving fuel once you’re there
The best way to do that is by using momentum and defensive driving techniques (basically reading the road) Hill climbing is the same, you cannot save fuel going up hills (if you’re driving correctly in the first place) modern engines with a nice flat torque curve spread over 500+ rpms mean that the fastest way is also the most fuel efficient way, the enemy of fuel economy is replacing lost momentum, so it figures tha the faster you crest a hill, the less momentum you need to recover, so in effect you shorten the length of the hill by going up it faster
I have done a test of sorts on one particular climb that some of you may know, it’s heading north from Baker (home of the Worls’s largest thermometer) on I-15 in California towards Las Vegas. The climb is one of 16 miles and it starts out as a bit of a drag, then gets steeper and steeper all the way to the summit. Driving up there downshifting at 1100rpm and splitting gears I end up in 6lo, so that’s five gearshifts, but as the gradient changes there’s a bit of tooing and froing between 6hi and lo along the way, my fan kicks in after the shift down into 7hi and my EGT (Exhaust Gas Temperature) climbs from 600c to 1000c, the truck has worked very hard pulling this hill and the turbos are pushing over 60psi of boost. The other method, and the one I use everytime now, is to split down to 8lo immediately before the climb, then as soon as the rpms drop below 1400 I change down to 7lo and keep my foot flat to the floor, the turbos fluctuate between 30 and 60psi, the EGT never climbs above 800c and I’m 10mph quicker at the top. MY indash instant mpg readout drops to 3.1mpg against the 2.6mpg minimum when doing it the other way and with just a flick of a switch and a single gearshift, it’s a ■■■■ sight easier on the driver