Fuel Misers

[smutchin]

I gotta say it's rather irksome when on a motorway and people slow down going up a hill. I always figured it's because they're too scared o press the accelerator, a bit like when they pull out of a junction and are scared to accelerate like that's the wrong thing to do!

In my car, it's not a matter in which I have a choice.

 

[Tin Pot]

Another explanation could be that their car just isn't powerful enough to maintain 70 mph when going uphill, and they haven't set out deliberately to annoy you.

Yep. 1.2L engines and below should be outlawed on dual carriageways and motorways.

 

[mjr]

Wind resistance increases as a square of speed, regardless of whether you're on a level road or driving up a hill.

Hills shelter you from headwinds a bit.

 

[mjr]

Yep. 1.2L engines and below should be outlawed on dual carriageways and motorways.

I've driven a 0.9L Fiat which was more than happy to accelerate to 70, but was pretty noisy with it.

 

[gbb]

Petrol engines are generally at their most efficient with a fully open throttle and rpm around the point where the engine develops maximum torque.
(Efficiency in this case being kg fuel per kWh and not mpg, which is not actually a measure of efficiency).

No doubt true but that doesn't help in real world driving when all you have is the o board display...the nearest / only thing you have to gauge efficiency at that moment.

Another explanation could be that their car just isn't powerful enough to maintain 70 mph when going uphill, and they haven't set out deliberately to annoy you.

Or in my case, i just have a different driving style to 'must maintain speed'..a more relaxed style.

 

[raleighnut]

I hope it's not the newer 2.5 engine as it will go pop, sure as eggs is little green apples. If it's the old 2.0, then as you were, map away, more the merrier.

It's the 'old' 2.0 litre motor, it lives a pampered life now though as Scott only taxes it for 6 months a year, he normally drives his van everywhere.

 

[mustang1]

Another explanation could be that their car just isn't powerful enough to maintain 70 mph when going uphill, and they haven't set out deliberately to annoy you.

Possibly... but i thought all cars could drive at 70? Anyhooo... this happens to me regularly when on north circular road at 50! Fifty!

 

[mustang1]

You can on mine (skoda superb). I set the cruise control, tap in the destination into the sat nav, close my eyes and sleep.

yeah it turns on the motorway too... but get eerily close to the lines before it figures things out good safety device though.

 

[DaveReading]

Worked example here, although the numbers used for the weight of the car and its max level speed don't look particularly representative.

 

[swansonj]

Worked example here, although the numbers used for the weight of the car and its max level speed don't look particularly representative.

I'm sorry, but that is a worked example of the speed a car can travel up a hill (and simplistic at that, as it doesn't make any allowance for resistive force f varying with speed). It doesn't seem to say anything about efficiency, which is what we are addressing here.

 

[DaveReading]

I'm sorry, but that is a worked example of the speed a car can travel up a hill (and simplistic at that, as it doesn't make any allowance for resistive force f varying with speed). It doesn't seem to say anything about efficiency, which is what we are addressing here.

No need to apologise, I'm aware of what it's about. It's relevant to earlier posts about the ability (or not) to maintain speed going up a hill.

BUT I gotta say it's rather irksome when on a motorway and people slow down going up a hill. I always figured it's because they're too scared to press the accelerator

and simplistic at that, as it doesn't make any allowance for resistive force f varying with speed

The worked example comes out with a pretty minimal effect on speed with the numbers it uses, so ignoring the variation of rolling resistance and aerodynamic drag vs speed is a not unreasonable simplification under the circumstances.

 

[mjr]

It's one of the options on the BMW Eco mode. I think Audi do the same.

www.viamichelin.co.uk has an eco setting which I think includes this, if your usual satnav doesn't.

 

[Jason]

Possibly... but i thought all cars could drive at 70? Anyhooo... this happens to me regularly when on north circular road at 50! Fifty!

you are away the section from Hangar Lane up to Finchley has average speed cameras now (50mph) ?

 

[Jason]

It's one of the options on the BMW Eco mode. I think Audi do the same.

yes ECO mode lowers the air con, and throttle response. auto stop/start is switched back on, if the driver had over ruled that in comfort mode. Sat Nav needs "eco mode" to be selected for it to find the route with least amount of traffic, but that can add many miles to a journey

 

[Tim Hall]

(Avoiding hills)

It's one of the options on the BMW Eco mode. I think Audi do the same.

I think you can get it for bike sat navs too. It's called the Ditchling option.