Fuel price discussion thread (was ‘chaos’)

Just waste of fuel to brake when not really needed is my point. Not here for a never ending argument and it seems I need to find some steeper motorways
 
[TW]Fox said:
The speed limit on a Motorway is 70mph unless otherwise signposted and you've set the cruise control to 70mph. So it'll maintain 70mph, either by using more power up a hill or using the brakes down a hill.
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The most fuel efficient way is to reduce speed going up the hill to the point where you coast down it and you reach the bottom at which point if done correctly you will be at 70 mph.

Scania's do this as well as many other trucks. I am surprised cars use a system where they brake down hill which as already mentioned is just wasted energy.
 
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Depends how steep the hill really. Don’t think you’ll be too popular slowing down to 50mph just to stop your car reaching over 70 down the hill. I think we’ve gone way past the original point of cars speeding up and slowing down continuously, on a flat motorway important to add that, but just so they can remain in the middle lane rather maintaining a set speed and using all 3 lanes.
 
adam cool dude said:
I am surprised cars use a system where they brake down hill which as already mentioned is just wasted energy.
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Not as surprised as I am that people cannot understand why a car has a system that prioritises compliance with the speed limit (Most drivers will set a cruise control speed with this in mind) over wasting energy. Cruise control has always been about driver convenience over fuel consumption anyway.

Most people set the cruise control to a speed they do not wish to exceed.
 
@Scania an infidelity, but have you tried the mercedes predictive powertrain control - seems that may be more advanced/economic than our four wheelers acc


Also, the intelligent cruise control and transmission control use the momentum on downhill stretches by automatically adapting the speed. The system exceeds the set speed (upper hysteresis) of the cruise control for a maximum of 40 seconds to allow the truck to make use of its momentum on the subsequent uphill gradient. Also, before the downhill stretch, PPC selects the gear which ensures optimum use of the continuous brake, thus going easy on the service brake – an advantage particularly for heavy trucks travelling downhill. Before an uphill gradient, the system decides automatically if a gear downshift is required. At the end of the ascent, the output is adapted once again, because PPC can detect in advance before reaching the brow of the hill whether the truck has sufficient speed to roll over the brow. If it does, it tolerates a temporary slowdown to a speed lower than the speed set in the cruise control.

I'm thinking I've already experienced this from lorries in my rear view mirror
 
[TW]Fox said:
Not as surprised as I am that people cannot understand why a car has a system that prioritises compliance with the speed limit (Most drivers will set a cruise control speed with this in mind) over wasting energy. Cruise control has always been about driver convenience over fuel consumption anyway.

Most people set the cruise control to a speed they do not wish to exceed.
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My van has a speed limiter function which is designed to stop you exceeding a set speed. Cruise control is about maintaining a set speed, nothing to do with compliance of the law otherwise 70mph would be the highest you could set it.
 
[TW]Fox said:
Not as surprised as I am that people cannot understand why a car has a system that prioritises compliance with the speed limit (Most drivers will set a cruise control speed with this in mind) over wasting energy. Cruise control has always been about driver convenience over fuel consumption anyway.

Most people set the cruise control to a speed they do not wish to exceed.
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Isnt this thread about fuel costs and ways to minimise.
 
[TW]Fox said:
Exactly.
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The cruise control systems of some vehicles incorporate a "speed limiter" function, which will not allow the vehicle to accelerate beyond a pre-set maximum; this can usually be overridden by fully depressing the accelerator pedal. (Most systems will prevent the vehicle from increasing engine speed to accelerate beyond the chosen speed, but will not apply the brakes in the event of overspeeding downhill, nor stop the car from going faster than the chosen speed with the engine just idling.)

On vehicles with a manual transmission, cruise control is less flexible because the act of depressing the clutch pedal and shifting gears usually disengages the cruise control. The "resume" feature has to be used each time after selecting the new gear and releasing the clutch. Therefore, cruise control is of most benefit at motorway/highway speeds when top gear is used virtually all the time. The speed limiter function however does not have this problem.
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This is exactly how it functions on my current van and the one previous.

en.m.wikipedia.org

Cruise control - Wikipedia

en.m.wikipedia.org en.m.wikipedia.org
 
My BMW won't overspeed going down a hill. It does engage the 'efficient dynamics' where the battery is charged by the road not the engine but won't overspeed and changes down to maintain speed going up hills too.
 
£2.029 for V Power unleaded, had 3ppl off that due to an offer in the Shell Go app and also had another offer for a free bag of crisps for next time :cry: , guess that softens the blow a little....

Also get 3% off 60l of Shell fuel per month due to being an energy customer, but I'm not sure if that automatically gets applied when paying via the app?
 
jpaul said:
@Scania an infidelity, but have you tried the mercedes predictive powertrain control - seems that may be more advanced/economic than our four wheelers acc


Also, the intelligent cruise control and transmission control use the momentum on downhill stretches by automatically adapting the speed. The system exceeds the set speed (upper hysteresis) of the cruise control for a maximum of 40 seconds to allow the truck to make use of its momentum on the subsequent uphill gradient. Also, before the downhill stretch, PPC selects the gear which ensures optimum use of the continuous brake, thus going easy on the service brake – an advantage particularly for heavy trucks travelling downhill. Before an uphill gradient, the system decides automatically if a gear downshift is required. At the end of the ascent, the output is adapted once again, because PPC can detect in advance before reaching the brow of the hill whether the truck has sufficient speed to roll over the brow. If it does, it tolerates a temporary slowdown to a speed lower than the speed set in the cruise control.

I'm thinking I've already experienced this from lorries in my rear view mirror
Click to expand...

I have used this and it is the ultimate way to save fuel but it is extremely slow. Traffic behind will get extremely frustrated as you slow down. You will start coasting way before a roundabout for example barely using any brake what so ever. Scania use a similar system but only works on hills. It will slow you down going up a hill and in theory when you get to the bottom you are doing 56mph. It is pretty annoying not because it isn't a good system but other lorries will overtake because you are slowing down then you end up overtaking them again and it ends up as a game of cat and mouse which is frustrating for both. Especially on hilly parts like the M62 or A1M towards Leeds/Newcastle.

Normally I will override it and just retarder/exhaust brake going down hill to stop it going over 60mph. If the road is empty however I just let it do its thing.
 
jpaul said:
@Scania an infidelity, but have you tried the mercedes predictive powertrain control - seems that may be more advanced/economic than our four wheelers acc


Also, the intelligent cruise control and transmission control use the momentum on downhill stretches by automatically adapting the speed. The system exceeds the set speed (upper hysteresis) of the cruise control for a maximum of 40 seconds to allow the truck to make use of its momentum on the subsequent uphill gradient. Also, before the downhill stretch, PPC selects the gear which ensures optimum use of the continuous brake, thus going easy on the service brake – an advantage particularly for heavy trucks travelling downhill. Before an uphill gradient, the system decides automatically if a gear downshift is required. At the end of the ascent, the output is adapted once again, because PPC can detect in advance before reaching the brow of the hill whether the truck has sufficient speed to roll over the brow. If it does, it tolerates a temporary slowdown to a speed lower than the speed set in the cruise control.

I'm thinking I've already experienced this from lorries in my rear view mirror
Click to expand...

Not tried the Mercedes system as of yet, I’ve heard it’s pretty good just a shame the truck it’s fitted to is largely derided these days (Mercedes trucks are not what they once were).



adam cool dude said:
I have used this and it is the ultimate way to save fuel but it is extremely slow. Traffic behind will get extremely frustrated as you slow down. You will start coasting way before a roundabout for example barely using any brake what so ever. Scania use a similar system but only works on hills. It will slow you down going up a hill and in theory when you get to the bottom you are doing 56mph. It is pretty annoying not because it isn't a good system but other lorries will overtake because you are slowing down then you end up overtaking them again and it ends up as a game of cat and mouse which is frustrating for both. Especially on hilly parts like the M62 or A1M towards Leeds/Newcastle.

Normally I will override it and just retarder/exhaust brake going down hill to stop it going over 60mph. If the road is empty however I just let it do its thing.
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Ageee Adam, Scania’s system is very good at saving fuel, at the potential of causing accidents behind you, the way it anticipates hills and effectively coasts over the brow (whilst shedding speed rapidly with no brake lights showing) has nearly had me rear-ended a few times , it won’t hold your speed on the downhill part either, the truck will happily run off the clock if you don’t pay attention….

I believe it works better on downhill sections if you have a retarder fitted, in all my years of driving however, I’ve only driven one truck with one! - I don’t know why they don’t incorporate the exhaust brake at least, into the system , it’s fairly good at regulating speed and - on Scania’s at least - displays the brake lights when it’s operating.
 
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