Motorway lower speed limit trial

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Timeandleisure

Timeandleisure

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Ok. Fuel injectors deliver a fixed amount per shot. Increase the frequency of those shots by increasing the rate of revolutions per unit time and therefore more fuel is used. The more heavily loaded a powertrain is, the more stress (ok, technically strain) is placed on it and therefore more quickly it’s internal lubricating and transmissions fluids are consumed.

Wind resistance from 60 to 70mph doesn’t increase by 36% in the real world. The aerodynamics of modern cars are tuned pretty well to peak efficiency at modern motorway speed limits. So, wind resistance is broken down into a number of factors, in no particular order these are:

block coefficient (the size of hole needing to be punched through the air).
Skin friction, directly proportional to wetted area.
Rate of change of profile.
Stagnation zones.
Parasitic drag.

Then there are road friction, powertrain losses and aero: noise effect losses to account for.

Air is a strange fluid to move through. It takes more energy to get up to a speed (any speed) above the aero effect boundary than it does to stay there. Then, taking all of the points above:
A low, narrow car has to bore a smaller hole than a tall, fat one.
A car with low rate of change of shape (long and pointy) pushes air more efficiently out of the way than a short and fat one.
A car with smaller surface area is less subject to skin friction and, higher in the speed regime, parasitic drag, than one with more surface area (this directly contradicts the long & pointy issue btw).
A car with poorly designed transition zones can leave stagnation areas, where the air rolls like a comber on a beach and attempts to suck the car backwards.

The undersides of cars used to get zero attention, now they have all sorts of aero channels to reduce or eliminate topside aero problems. Those funny shaped wheel arches contribute useful percentages of aero efficiency improvements.

Add all that together and we arrive at (generally) long, low, smooth & sleek cars being the best at aero, however costing significantly more in materials and labour than small, rounded or flattish sided vehicles so therefore being less efficient to manufacture.

None of this is basic physics either..!

So, we then get to the argument: what is best to reduce fuel burn? Well, burning the least amount of fuel per mile of course. So it follows, one can theoretically design a long, low, sleek vehicle with a given engine that, on a straight flat road, for the mass of that car and for a given drivetrain setup, will produce engine revolutions and therefore fuel burn per unit time that equal the fuel burn of a short, fat vehicle at a lower speed. The issue then includes controlling the total units of time that such a car spends on the road, which is determined by its speed. The time taken makes no difference the emissions per mile, but then conversely the emissions per mile also make no difference to the total emissions per journey if the journey takes 15-20% longer in time for a car optimised for a higher cruising speed.

Natural warming and cooling has not always taken millennia, there was a cooling period that took around 2 centuries late in the first millennium that lasted to, well, around now; also there was one around the third millennium BC that again took in the order of several centuries start to finish to begin and then revert back.

You do realise that Peak Oil as a theory has long since been exploded? Oils sands and shales cost more to recover due to the economies of scale of the kit utilised; the infrastructure for a deep sea rig system is enormous in comparison.

The IPCC data and the UN reports are all available by searching online. I’m in a meeting at work so right now don’t have the time to dig it out for you, but they’re publically available.

The reforestation is a natural process not any form of government initiative. Do you think that nature just stops..?! Again, google it. Many articles showing secondary and tertiary rainforest regrowth in surprisingly short timescales.
Totally agree with your conclusion only trouble is there is no money in it... (not talking about us mere mortals)...
p.s. came out of a meeting to read your post :)
 

Craiglxviii

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[QUOTE="Craiglxviii, post: 1856777, member: 77153" ... which is why ships are long and narrow with pointy ends, .....

they have a pointy end & a blunt end :rolleyes:[/QUOTE]
Yep, the pointy back end is to prevent stagnation.

Look at the front end of an air- dropped torpedo, it has a stagnation cup to allow for easy water entry.
 

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Which ever pollution you wish to highlight, in free flowing traffic it will go up per mile with increase of speed.

For me climate change arguments went out about a decade ago, man made climate change denial seems to fit nicely alongside 5G being responsible for Covid.

True that we are no where near peak oil, but from now on in ts extraction and processing will be increasingly environmentally damaging. And even if it wasn't, considering the damage we now know it causes we really do need to start to move away form it as soon as possible.

The planet is grossly over populated, we are currently using our resources 60% above a long term sustainable manner.
https://www.footprintnetwork.org/our-work/ecological-footprint/
And bear in mind the damage that has been done so far is by less than a one billion of us, and the other 6 billion are desperately trying to adopt our livestyles. If all 7½ billion of us enjoyed the lifestyles we have in the UK, we would need another 5 planets to provide a long term sustainable future! Another couple of billion people is the very last thing we need right now.

We are currently wiping our our ecosystems at an alarming rate, and even if you don't accept the moral argument that this is a bad idea, then you do need to accept that wiping out what we fundamentally rely upon is beyond crazy.
And you still bought a 2020 diesel?
 
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Craiglxviii

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Timeandleisure

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You’re most welcome. And... due to a number of factors- total waste of a day!
Hahaha... your waste my gain as I am definitely equipped with more information than I was this morning from great thought provoking conversations :geek:
 

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And you still bought a 2020 diesel?
It would have been nice to go electric however part of what I do requires me to take quite long journeys at very short notice, then when I'm away I certainly don't want the hassle of worrying about getting it charged up. The wonderful thing about fossil fuel is refuelling is fast and very convenient, and at the moment electric is still a bit of an unknown.

So then there is the choice between diesel and petrol. Diesel is by far the best when it comes to CO2 and climate change, Petrol is far better in cities where it produces less of the health damaging pollutants of NOx and particulates. As I live rural and are seldom in towns let alone cities then I believe diesel is still the best for me, I will create about 2 tonnes less CO2 in the next 4 years than if I had went petrol.

One of the main criteria I put on my next car was excellent mpg, and if our choice is as good as the same 200d B Class courtesy car with the that we still have. Then I believe we will have chosen well. it has achieved 65mpg over its first 450 miles with a 78mpg on one run. and that is pretty impressive for a brand new car, when this engine lossens up after 5k I would expect up to another 5 or 10%
mpg-1124.jpg


I know I am not setting a good example with my 5.4 litre V8, but I do try to do my bit for the planet. I now only drive into work 2 days a week instead of 5, which is one good thing to come out of COVID.

We have a more economical car, but the Merc always comes out on a Sunny day.

I think people need to travel less, sorry I really do. Foreign holidays, airline and ship leisure travel and chucking plastic in the sea really get my goat. Loss of Biodiversity is horrendous in the UK and elsewhere.

There was a video of the sea floor in the Marianas trench or somewhere, 7 miles under the ocean, and guess what, there was some plastic in shot and a plastic office chair.

Horrible.
Nthing wrong in having something mad to drive, it would be a bit irresponsible for an everyday car, but for the occasional sunny day, why not? I do love my cars even though I'm probably coming across as extinction rebellion wannabe :D
 

Craiglxviii

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Be aware that you’ll likely see negligible improvement over the engine’s running in period, mainly because they are so finely machined nowadays that there isn’t such a period any more.

Like you, I have to undertake potentially countrywide journeys at potentially short notice. What better to do them in than an S Class platform? And, if one can find an engine that never struggles, that’s a match made in heaven...
 

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I have full V8 owning permission as my Carbon footprint is low, work from home 5 days a week, only use the car for long journeys not start stop, I ignore speed limits and only drive at speeds economical to the engine, it is Petrol as I have children and do not want to annihilate their lungs, and I used to own a Hybrid and drove regularly in it at 15mph so only electric motor working.....

I no longer fly annually to Bali in business for my vacations (where I would have been now) but spend the time planting vegetables in the garden thanks to Covid, so my conscience (if I had one) is clear!

Mercedes SL500 R231
 

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I struggle to see how buying any new car saves the environment...:confused:

The one you have has already been made and the environmental costs have already been accounted for...:cool:

Buying new means disposal of your old one, or if being sold on there will most likely still be a vehicle down the line that will be scrapped. So raw materials and energy being consumed to manufacture and transport your new vehicle and energy and transportation in disposing of your old on.

Maintaining the one(s) you have is better for the environment but not so good for economies or business, which is what the push for "green" is really about.

I don't believe for even a yocto second that you can "buy" yourself "Green" despite the marketing and legislation to the contrary.
 

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So why isnt anyone standing up for the petrol head / car lovers ?? Its always the same in this country , fossil fuel vehicles are the devil and get battered at every possible turn yet known states any opposing arguments? We have more than enough folk with money , power and influence but all go into hiding when they could be defending the ICE car owner
 

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I struggle to see how buying any new car saves the environment...:confused:

The one you have has already been made and the environmental costs have already been accounted for...:cool:

Buying new means disposal of your old one, or if being sold on there will most likely still be a vehicle down the line that will be scrapped. So raw materials and energy being consumed to manufacture and transport your new vehicle and energy and transportation in disposing of your old on.

Maintaining the one(s) you have is better for the environment but not so good for economies or business, which is what the push for "green" is really about.

I don't believe for even a yocto second that you can "buy" yourself "Green" despite the marketing and legislation to the contrary.
Couldn't agree more but I'm not the only one in this household. The green solution in the vast majority of cases is to keep what you have.

The car we are buying probably generated around 12 tonnes of CO2 in its production and delivery. (these figures are never known but I believe 12t would be a reasonable and low ball park figure)

If our new car gets 60mpg as opposed to our last cars 45mpg
This would be a saving of 25.2 ml of diesel per mile
or equivalent to 66 grammes less of CO2 per mile

Therefor payback time would not be for 181,000 miles

Of course cars do eventually come to the end of their lives and need to be replaced, and the above figures do not take that into account, but undoubtedly the desire to have new, and the desire of economies to create demand and spending is the big producer of CO2 and global warming.


So yes, you can't buy into being green, but if you are changing your car for whatever reason then buying a less environmentally damaging one is surely the way to go?
 
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Craiglxviii

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The total “emissions” (energy) input to build a car- from raw material winning to final assembly- is something like (I’m doing this from memory as I can’t find the study atm) 9% of a car’s expected lifetime energy consumption Now the catch is, that’s the 8.1yr first owner lifetime, the only one the car builder is worried about. So run that car beyond 8.1 years and the manufacturing energy fraction starts to drop. Actually, as we go into the future it drops more rapidly due to the lowering of the recovery energy fraction at lifecycle end for recycling/ reprocessing, as our recycling technologies improve hand over fist. Again, just from memory that energy fraction is around 1.0- 1.5% (all the metals & glass have to be remelted and reprocessed, the highest consumers of input energy).

So, we actually do have a situation whereby as automotive technology improves (EVs of whatever flavour), it will be “cheaper” in overall lifetime energy expenditure to actually crush an old cat and buy a newer one.
 

Craiglxviii

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Couldn't agree more but I'm not the only one in this household. The green solution in the vast majority of cases is to keep what you have.

The car we are buying probably generated around 12 tonnes of CO2 in its production and delivery. (these figures are never known but I believe 12t would be a reasonable and low ball park figure)

If our new car gets 60mpg as opposed to our last cars 45mpg
This would be a saving of 25.2 ml of diesel per mile
or equivalent to 66 grammes less of CO2 per mile

Therefor payback time would not be for 181,000 miles

Of course cars do eventually come to the end of their lives and need to be replaced, and the above figures do not take that into account, but undoubtedly the desire to have new, and the desire of economies to create demand and spending is the big producer of CO2 and global warming.


So yes, you can't buy into being green, but if you are changing your car for whatever reason then buying a less environmentally damaging one is surely the way to go?
Average family car produces around 24 tons of CO2 across its lifetime. Manufacturing emissions are therefore in the order of 2.0- 2.5 tons, not 12.
 

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