In a recent edition of the magazine Advanced Driving, a letter from a Mr Hyett of Kent suggests that the Government should seek to reduce carbon emissions from our motor vehicles as follows;
" ... surely the best way would be to fit all road vehicles with governors limiting their maximum speed to 56mph? This is the most efficient speed at which motor vehicles can drive - engine efficiency increases with speed, as does wind resistance, and the two intersect at 56mph."
"the most efficient speed" - I wonder if the magic figure of 80kph holds true for trains and aircraft as well or should we wait until Mr Hyett discovers the most efficient speeds for all other forms of motorised transport?
Can you imagine the size of the traffic jam as we all cruise at lorry speed?
I nearly choked on my Shreddies at this. What do you lot make of it?
Hawkeye
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Stranger in a strange land
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If that were the case we'd be driving like a line of zombies unless they drive up a slope where the cars may hold the same speed better then an artic could at 40 tonnes.
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Its not what you drive, its how you drive it! :-)
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the Government should seek to reduce carbon emissions from our motor vehicles
Yeah that'll solve global warming at a stroke.
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On a point of logice - I don't see how everyone moving at 'lorry speed' would actually create a jam
multiple vehicles at variable speeds - how exactly does that prevent traffic jams?
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As motor vehicles contribute only a tiny proportion of Co2 or whatever it is we are supposed to be worried about, it would not make a jot of difference. The control freaks would love it though.
8< SNIP non relevant comments removed - DD
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Speaking as someone with a highly obsessive nature, I know that the most efficient speed for my car is not 56mph, nowhere near. After trying thousands of combinations with the cruise and the trip computer over thousands of miles and thousands of journies, I get my best mpg at 42mph. Any lower and it starts hunting for third gear, any higher and the mpg drops. In fact the difference between 56mph and 42mph on a flat windless road is about 9mpg (38-47)
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I would agree with this, as I too have found the best mpg comes at around 45mph.
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Matchbox electric car track - every vehicle at the same speed - safe too! and never had a jam on my track
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On a point of logice - I don't see how everyone moving at 'lorry speed' would actually create a jam
I was assuming that there would be a marginal speed difference and that the 1 mph faster cars would try and overtake the slower cars. Just like HGVs do now except everyone would be doing it.
Hawkeye
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Stranger in a strange land
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Its true though.
In my van 56MPH = 72MPG
............... 70MPH = 55 MPG
(Punto Multijet)........................... 102 *free* miles every 6 gallons.
24 gallons a month =
408 free miles a month
4,896 free miles a year.
10 years = 48,960 extra *free*miles by doing 56MPH instead of 70MPH....
Thats around £9,792 saved over 10 years (at £5 a gallon.)
OK rough figures, I`m tired, but someone tell me i`m WAY out here or I just convinced myself to travel at 56MPH :)
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I cannot believe it is an arbituary 56mph, surely it would be the lowest speed the car can do efficiently in its highest gear and that will change with road gradient.
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During the last petrol crisis, I took to driving the old Mondy at 50-55mph and I was still going long after the roads had emptied of traffic ;-)
We'll know when petrol is too expensive because at that point folks will reduce their speed. We ain't there yet by a long way.
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During the last petrol crisis, I took to driving the old Mondy at 50-55mph and I was still going long after the roads had emptied of traffic ;-) We'll know when petrol is too expensive because at that point folks will reduce their speed. We ain't there yet by a long way.
Hmm High Wycombe to Dumbarton in 11 hours with the stops on the way every 2 hours or so hmm fly to Glasgow? Oh no that's even worse for the enviroment!
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Its not what you drive, its how you drive it! :-)
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Hawkeye, (and other posters to this thread) please forgive the pedant in me, but 56 mph is actually 90 kph, not the 80 kph mentioned.
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Hawkeye, (and other posters to this thread) please forgive the pedant in me, but 56 mph is actually 90 kph, not the 80 kph mentioned.
.............please forgive the pedant
in me, but 56 mph is actually 90.123264 kph (correct to 6 places of decimals), not the
80 kph mentioned. ;-)
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L\'escargot.
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My Hyett needs to realise that in fact the 'most efficient cruising speed' will be different for every vehicle and in every circumstance (wind direction and speed, gradient, etc.)
The premise which his entire theory is based on is false, doesn't say a lot for the idea.
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In the "Car Clinic" section of the Sunday Times, it states that a Focus 1.6 TDCI should return 62.6 mpg.
At what speed would you have to drive to get this figure? Possibly you would have to start at a high altitude and come down.
I have found that the advice in the "Car Clinic" is often nonsence, they once advised that you should let your car warm up at tickover before starting a journey, because most wear is in the first few miles! So it would be OK to let it wear at tickover and annoy the neighbours.
You can't beat HJ in the Telegraph on Saturdays.
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Technically the most efficient speed is where the engine is running at maximum efficiency. This usually means relatively low RPM (about 1600-2000rpm in a diesel and 1900-2500rpm in a petrol) and relatively open throttle of about 80%. The trick then is to translate that power and engine speed by gearing to that which is required to move the car at a constant speed through gearing. In other words gear such that the engine is running at that speed at your desired constant speed. It is even preferable to be slightly below that speed so that the engine is at the very bottom of where it is most efficient, thus any *slight* increase in speed makes things more efficient not less. The reason this isn't done is because if it were done in 'ideal' conditions then you wouldn't be able to accelerate in top gear on anything other than a flat road, because the power of the engine would exactly equal the amount of power needed by the car on a hill. Hence it only would really work with an auto transmission in charge to shift down a gear as required.
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Thread tidied up and some non relevant and argumentative comments removed. Some genuine posts *may* have been lost in the tidy up, which unfortunately was unavoidable.
DD
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With 20% of all CO2 emmissions coming from farm livestock, surely all our cows should be fitted with filters! Let alone the huge amount coming from other natural sources like volcanoes and underground coal fires, or un-natural sources like power generation, heating, industrial uses, etc.
If the car was the only source of CO2 emmissions then perhaps Mr Hyett's suggestion would be a valid arguement for economical emmission driving. It is not, so would never make any real impact to total CO2 emmissions.
All the tinkering with reducing a car's CO2 emmissions will only make a 1-2% reduction in the total CO2 emmissions, therefore unlikely to have any major effect.
In my opinion global warming is not caused by CO2, but solar activity, as this is complete outside our control. The people who promote the global warming theory (including the Stern Report) have tried to deny that during the MIddle Ages the earth was 3 degrees centigrade warmer than today. That was before massive population growth, industrialisation and the internal combustion engine. How did the warming of the globe happen? Only 20 years ago there were people talking of a new ice age, where has that gone?
For more information read these 2 long articles by Christopher Monckton:
The sun is warmer now than for the past 11,400 years
tinyurl.com/t4h8e
Wrong problem, wrong solution
tinyurl.com/ycv6bj
Do read these 2 articles as they will change your mind on global warming.
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Roger
I read frequently, but only post when I have something useful to say.
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No doubt next year Viscount Monckton will be giving us his new improved value of pi, a patent for a perpetual motion machine, and proof that smoking doesn't cause lung cancer. Clever chaps these amateur dabblers.
If we're posting random links, then try these two, directly discussing the viscount's witterings in the Telegraph:
www.guardian.co.uk/commentisfree/story/0,,1947248,...l
www.realclimate.org/index.php/archives/2006/11/cuc.../
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"amateur dabblers"
So what exactly are George Monbiot's qualifications to comment on climate change? All I can find is that he is an ex-architect, which hardly qualifies him as more than an "amateur dabbler" Why should we take more note of him than Monckton?
Figures quoted in this (and other)threads are pretty close to what the IPCC quotes - and that is that if you removed EVERY car from the world , it would make no real difference to CO2 levels and hence to "global warming". Oh, and by the way, the IPCC reckon that world temps have increased by 0.6 deg C since 1880, yet they can only estimate global temps in 1880 to be 14 deg C (+ or - 2 deg C) - - so have global temps increased? They can't be definite!
Try looking up
Milutin Milankovitch / Milankovitch cycles and then see if you think that taxing cars will have any effect whatsoever on global temps.
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Phil
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"Do read these 2 articles as they will change your mind on global warming"
The articles are a disgrace, sham science at best.
If you want to justify cars, why not concentrate on the fact that electricity generation has a far bigger impact than cars ever will. At least that's based in science not poppycock.
If you want science, have a look at the RealClimate website referred to by KMO. At least that's written by real climate scientists and knows what it's talking about.
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8< SNIP
Potentially defamatory comments removed - DD
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