Fuel efficiency

rob22888 · 26 February 2016 08:08

newmercman:
That’s the way to do it, cruise control cannot see, so it will keep throwing fuel at the engine until it reaches the predetermined speed, therefore it should only be used on flat ground, in rolling hills you use the momentum of the vehicle to do as much of the work as possible.

Modern Scania’s can see to a certain extent, they have a GPS ariel on the roof linked to a database that knows the gradients. If CC is set It will automatically kill the power on the approach to the crest of a hill and leave it killed as you go down the other side.

newmercman · 26 February 2016 08:17

Yes the next generation GPS linked CC are pretty clever, they can also run different states of tune as the truck encounters different terrain, giving more torque in hilly parts and cutting it back on flat ground.

Clever, but another step towards dumbing down drivers even further, pretty soon a chimpanzee will be more than capable of being a lorry driver.

rob22888 · 26 February 2016 08:35

newmercman:
Yes the next generation GPS linked CC are pretty clever, they can also run different states of tune as the truck encounters different terrain, giving more torque in hilly parts and cutting it back on flat ground.

Clever, but another step towards dumbing down drivers even further, pretty soon a chimpanzee will be more than capable of being a lorry driver.

I guarantee there will be a team of boffins in an office somewhere figuring out how to make trucks automatically reverse onto bays. That really would be the start of the end. If they can make cars park themselves it’s only a matter of time.

cav551 · 26 February 2016 09:11

I almost never use full throttle and try if possible not to bring the vehicle to a halt. In town traffic with potentially many traffic lights, I hang back from the traffic and aim for about 20-25 mph maximum - it is so much less stressful as well.

bluey_circles · 26 February 2016 09:29

Javiatrix:

bubsy06:
Stick it in neutral at the top of a hill and let it go, not recommended if u have a panic attack if an overspeed pops up on the tacho

Never do this if you’re aiming for low fuel consumption. The 100+ MPG you’ll be achieving will still be more than the ∞ MPG you’ll achieve by leaving it in gear with your foot off the gas.

It is fun for seeing how fast you can make the lorry go though

It very much depends on the hill, on a gentle slope it may be possible to roll at 45 and not loose or gain speed, so you may get a mile with just tick over as consumption (3l per hour tick over at 45mph would be equivalent 70mpg) If you come onto the overrun fuel is cut, so 0 mpg but the slowing effect of the engine would require you to come back onto the throttle. Turning an engine over requires a huge amount of energy, and when on the overrun this energy is coming out of your momentum, this is why we use the overrun to slow the vehicle.

However and very importantly, rolling in a manual should never be done as it is contrary to the highway code (so clearly very dangerous) . But many / most auto boxes are now using this tactic, such as volvo’s iRoll.

I agree with many other comments in this thread, forward planning is the best for good mpg, braking is such a vast waste of energy it needs to be kept to a minimum, rolling and using the gears to slow is far more economic. Also speed plays a huge part, sitting at 40 would be vastly more economic than sitting on limiter.

radar19 · 26 February 2016 09:39

I do recall that iRoll can only be used when CC is engaged because you can set a speed where the exhaust brake will kick in when the truck exceeds it so in a way keeping the wagon under control as you aren’t letting it just free wheel like you would in a manual.

milodon · 26 February 2016 21:04

BradCarTransporter:
Don’t accelerate aggressively, we are asked not to use more than 95% of the pedal travel (our trucks don’t have kick down anyway or any manual gear selection for that matter)

this is actually false, as you only need to take it easy for the first few gears, to prevent wheelspin on wet tarmac and the engine simply revving its ■■■■ off. after that, floor it.

I remember switchlogic claiming the easy approach to be better in a thread started by jessicas dad regarding fuel consumption, but it got locked before I could reply.

I was still wondering about that, until I booked a session with the driving instructor at the local Volvo dealer. he assured that I was correct and he should know - there is a little competition called Volvo Drivers Fuel Challenge, it’s worldwide and he coached number three.

milodon · 26 February 2016 21:07

Radar19:
I do recall that iRoll can only be used when CC is engaged because you can set a speed where the exhaust brake will kick in when the truck exceeds it so in a way keeping the wagon under control as you aren’t letting it just free wheel like you would in a manual.

iRoll will function without CC as well, it will just put it back in gear at 99kph. if the CC is on, it will use the exhaust brake, if it off, it won’t

bluey_circles · 27 February 2016 01:17

rob22888:
I guarantee there will be a team of boffins in an office somewhere figuring out how to make trucks automatically reverse onto bays. That really would be the start of the end. If they can make cars park themselves it’s only a matter of time.

Future trucks will pretty much drive themselves, I imagine the roll of the driver will primarily to be the scapegoat. When the electronic wizardry goes pear shaped and someone dies, someone will need to go to prison, and this will be the function of the driver.

newmercman · 27 February 2016 05:50

milodon:

BradCarTransporter:
Don’t accelerate aggressively, we are asked not to use more than 95% of the pedal travel (our trucks don’t have kick down anyway or any manual gear selection for that matter)

this is actually false, as you only need to take it easy for the first few gears, to prevent wheelspin on wet tarmac and the engine simply revving its ■■■■ off. after that, floor it.

I remember switchlogic claiming the easy approach to be better in a thread started by jessicas dad regarding fuel consumption, but it got locked before I could reply.

I was still wondering about that, until I booked a session with the driving instructor at the local Volvo dealer. he assured that I was correct and he should know - there is a little competition called Volvo Drivers Fuel Challenge, it’s worldwide and he coached number three.

Spot on, you go gentle in the low range and then flat to the boards until cruising speed, as long as you keep the engine in the green band you will get the best economy and performance from the truck.

The way a modern diesel is designed means that the most economical way to get up to speed is also the quickest way, combine this with good awareness and avoiding unnecessary braking and you will get the best from it.

carryfast · 27 February 2016 13:38

newmercman:

milodon:

BradCarTransporter:
Don’t accelerate aggressively, we are asked not to use more than 95% of the pedal travel (our trucks don’t have kick down anyway or any manual gear selection for that matter)

this is actually false, as you only need to take it easy for the first few gears, to prevent wheelspin on wet tarmac and the engine simply revving its ■■■■ off. after that, floor it.

I remember switchlogic claiming the easy approach to be better in a thread started by jessicas dad regarding fuel consumption, but it got locked before I could reply.

I was still wondering about that, until I booked a session with the driving instructor at the local Volvo dealer. he assured that I was correct and he should know - there is a little competition called Volvo Drivers Fuel Challenge, it’s worldwide and he coached number three.

Spot on, you go gentle in the low range and then flat to the boards until cruising speed, as long as you keep the engine in the green band you will get the best economy and performance from the truck.

The way a modern diesel is designed means that the most economical way to get up to speed is also the quickest way,

There’s no way that it can be putting in less fuel at 100% accelerator input as opposed to less.IE the most ‘economical way’ regards fuel consumption can only be the slowest.

Unless they’ve invented a way to get more acceleration from less power and therefore less fuel and for fuelling to reduce as accelerator input increases.

However the relevant bit is that ‘slowest’ obviously isn’t the most ‘productive’ which is why no one is running around with Gardner powered trucks. In which case it’s then all about ‘specific’ fuel consumption at the type of horsepower output required to get the job done.It’s in ‘that’ case where the argument flat out and short shift well before the peak power rpm is reached and using the optimum part of the engine’s torque curve ( green band ), obviously wins out over the idea of just applying the type of accelerator inputs which turns a modern powerful truck diesel into something with the performance of a Gardner.IE there’s a difference between the equation the least fuel consumption for the least power as opposed to the least fuel consumption for the most power.

dipper_dave · 27 February 2016 14:00

I acheived more acceleration with less fuel today on the A14. Neutraled it on the ski slope before the M6/M1 section and fully laden got her up to 75mph (a new record for me but I was feeling dangerous). Much to the annoyance of the tipper trying to overtake who bottled it at around 65mph.

Epic fuel figures for that stretch and enough momentum left to virtually coast through the roadworks.

newmercman · 27 February 2016 16:41

Economy and productivity are the same thing really Geoffrey, at least in the real world of lorrying. However to avoid a 327 page argument, let’s swap economic for efficient.

disco_street · 27 February 2016 19:00

My place don’t even no anything about fuel efficiency but I get feed up with filling my pathetic 92litre tank up all the time, spend longer standing filling it up than loaded and offloaded my cars.

So Iv just stuck it on “econo” mode and it’s been better but still crap.

carryfast · 27 February 2016 19:09

newmercman:
Economy and productivity are the same thing really Geoffrey, at least in the real world of lorrying. However to avoid a 327 page argument, let’s swap economic for efficient.

That wasn’t meant as an argument nmm.More a case of just pointing out the confusion which seems to be applied to the issue of fuel consumption.IE slower will save fuel but it will also cost in lost earnings ( and reduce the road network to an ever reducing crawl ) so I was actually agreeing with you.IE the aim is as much power/speed as possible for the least possible fuel consumption.On that note running at 65 mph is arguably better than 50 mph.

newmercman · 27 February 2016 19:11

I know, I was being flippant.

papermonkey · 27 February 2016 19:32

Thrcompany I work for has gone to town on this matter and has started to use a firm called mix-telematics. It has a bit of kit in the cab monitoring excess idling, overspeeds,violent braking and the like.

bradcartransporter · 27 February 2016 19:50

milodon:

BradCarTransporter:
Don’t accelerate aggressively, we are asked not to use more than 95% of the pedal travel (our trucks don’t have kick down anyway or any manual gear selection for that matter)

this is actually false, as you only need to take it easy for the first few gears, to prevent wheelspin on wet tarmac and the engine simply revving its ■■■■ off. after that, floor it.

I remember switchlogic claiming the easy approach to be better in a thread started by jessicas dad regarding fuel consumption, but it got locked before I could reply.

I was still wondering about that, until I booked a session with the driving instructor at the local Volvo dealer. he assured that I was correct and he should know - there is a little competition called Volvo Drivers Fuel Challenge, it’s worldwide and he coached number three.

To be fair, I did say that these are points from my company memo. Unfortunately I’m in one of those jobs where it’s far easier to just do as management ask than it is to question them. They pay the fuel bill after all

bradcartransporter · 27 February 2016 19:54

papermonkey:
Thrcompany I work for has gone to town on this matter and has started to use a firm called mix-telematics. It has a bit of kit in the cab monitoring excess idling, overspeeds,violent braking and the like.

Dhl ?

mrflibble · 1 March 2016 16:25

Carryfast:
There’s no way that it can be putting in less fuel at 100% accelerator input as opposed to less.IE the most ‘economical way’ regards fuel consumption can only be the slowest.

Unless they’ve invented a way to get more acceleration from less power and therefore less fuel and for fuelling to reduce as accelerator input increases.

I’m not sure it’s as simple as that, once you put a gearbox into the question.

For example, from a standing start, using gentle accelerator input, it might take you, say, 1 km to get up to limiter speed. Now, if you were to floor it on the mid-range gears, is it going to use more or less fuel to cover the same distance? The obvious answer would be “more”, but by flooring it, you might get up to limiter speed in, say, 500 m, and then you’re cruising the second 500 m in top gear. Provided you’re not running the engine at ridiculously low revs, the most fuel-efficient gear is always going to be the highest one available, so IMHO, it’s perfectly possible that it could be more fuel-efficient to accelerate harder (within the green band) in the middle gears so that you’re spending less time in the inefficient gears, and getting into the more efficient gears quicker.

As for whether cruise control gives you better fuel economy or not, IMHO the answer is “in most cases, yes”.

Certainly there are situations where a human driver can do better than cruise control, by anticipating the future - for example, when driving over the Alps, I used to ease off before the summit of a hill and let the speed come down to, say, 70 kph, in the knowledge that going down the other side the truck would be accelerated back up to 90 kph for free by gravity. Of course, I’d only do this if there were nothing behind me . In this case, the fuel spent keeping the truck going at 90 kph going up the hill is going straight into the brakes on the downhill section, so there’s no point in maintaining full speed right up to the summit.

However, in flat cruising situations I think that cruise control will probably do a better job than most drivers because it will tend to react much quicker to the truck speeding up and slowing down, and make much more gradual changes than a human.

Of course, most drivers effectively spend the vast majority of their time on “cruise control” anyway, as that’s what basically happens when the truck is sitting on the limiter.