Member Since: 14 Dec 2013
Location: Herefordshire
Posts: 2083
Depends on many factors including the gearing of your car, but the wind resistance reduces dramatically, the slower one drives . Double the speed & you need 4 times the power to overcome the drag. This was shown dramatically when I was on a ferry to Sweden, that normally ran at about 22 knots on 4 engines ,had total power shut down due to an engine fire. Eventually they got one engine running and we were able to achieve 12 knots , when the second engine came on stream, 17 knots.
23rd Jun 2019 10:46 pm
RRSTDV8
Member Since: 07 Apr 2014
Location: Here
Posts: 13557
Speed = drag. Power required to overcome drag increases with the cube of the speed. Double the speed = 8 times the power required to overcome drag. Power comes from fuel. Thus higher speed means more emissions. You can go slower in a lower gear with more revs but still use less fuel and thus produce fewer emissions.Visiting from rrsport.co.uk
2012 RRS SDV6
2008 RRS TDV8
"When you fire that first shot, no matter how right you feel, you have no idea who's going to die! You don't know who's children are going to scream and burn. How many hearts will be broken. How many lives shattered. How much blood will spill, until everybody does what they were always going to have to do from the very beginning: SIT DOWN AND TALK!"
23rd Jun 2019 10:47 pm
mse
Member Since: 27 Jun 2005
Location: Shropshire
Posts: 2704
Gearing comes into play here though.
If the engine is doing 1500rpm - it is spinning at 1500rpm so you could be doing 50mph at 1000rpm in 8th or 50mph at 2000rpm in 4th. The engine needs more fuel to run at 2000rpm than it does 1000rpm
The amount of Drag will also change based on the vehicle and therefore the amount of engine speed required to maintain the relative speed (and therefore the rate the engine revolves) will change.
its all rubbishMike
24th Jun 2019 7:32 am
UNG
Member Since: 20 Jun 2008
Location: Lancs
Posts: 768
Never understood how vehicle emissions differ so widely
If a vehicle with a 2 litre engine does 50mpg and a vehicle with a 1 litre engine does 50mpg why are the resulting figures so different when both have burnt exactly the same amount of fuel or are the overall tests being distorted to favour smaller cars"Never keep up with the Joneses. Drag'em down to your level. It's cheaper".
24th Jun 2019 8:52 am
L319
Member Since: 14 Dec 2013
Location: Herefordshire
Posts: 2083
mse wrote:
Gearing comes into play here though.
If the engine is doing 1500rpm - it is spinning at 1500rpm so you could be doing 50mph at 1000rpm in 8th or 50mph at 2000rpm in 4th. The engine needs more fuel to run at 2000rpm than it does 1000rpm
The amount of Drag will also change based on the vehicle and therefore the amount of engine speed required to maintain the relative speed (and therefore the rate the engine revolves) will change.
its all rubbish
Its all about the amount of power required, which is not directly related to engine speed . If you look at instantaneous fuel consumption figues, it can often be lower at higher engine speeds , the trick is to keep the engine running at a speed where its lowest specific fuel consumption figure is lowest. ie where it is most efficient.
24th Jun 2019 12:22 pm
mse
Member Since: 27 Jun 2005
Location: Shropshire
Posts: 2704
Im not sure thats helping to prove that a 50mpg limit creates less emissions, which is the point
I could get the car to push out black smoke work really hard, but only do 20mphMike
24th Jun 2019 12:57 pm
Russell
Member Since: 23 Aug 2007
Location: Kent
Posts: 10564
mzplcg wrote:
Well, I know nothing about the national grid, nor the science behind EVs. Neither, IMO, do any of us truly know the impact of human activity on the environment. as a colleague once said to me (a scientist at a pharma company) "It's a very arrogant person who believes that the human race is able to take on Mother Nature and alter her course"
But, answer me this. If EVs are so clean, who accounts for the pollution in generating the electricity? It has to come from somewhere. Renewables are still scarce and also come with an envirnmental impact of manufacturing the kit in the first place.
Who accounts for all the pollution caused by the production of Lithium batteries? Mining, transport, manufacturing and ultimately recycling.
Are EVs any less polluting to manufacture than a petrol or diesel car?
I don't pretend to know the answers but having specific limits to improve air quality in a specific area does seem rather futile to me.
What are some of the biggest polluters, SHIPS and how does all this kit, batteries, wind turbines, EV get moved around the world, by SHIPS!!!!!!!!!!!!!!!MY17 D5 1st Edition Namib Orange
MY15 D4 HSE Kaikoura Stone
MY12 D4 HSE Nara Bronze Sold and gone
MY11 D4 HSE Stornaway Grey Sold and gone
D3 S spec Silver Sold and gone
Tow bar, full length roof bars, side steps, tow bar storage unit, surround camers.
D4 camera club
24th Jun 2019 3:12 pm
Russell
Member Since: 23 Aug 2007
Location: Kent
Posts: 10564
RRSTDV8 wrote:
GLYNNE wrote:
The network has never been in such a poor state of repair.
Why?
It’s all down to the foreign investors wanting the largest profit possible.
Surely not! Every Government since Thatcher has told us how privatisation increases investment, blah, blah etc. Surely these fine people wouldn't have been lying to us all these years...
Dont you believe it, the network is in a very very poor stateMY17 D5 1st Edition Namib Orange
MY15 D4 HSE Kaikoura Stone
MY12 D4 HSE Nara Bronze Sold and gone
MY11 D4 HSE Stornaway Grey Sold and gone
D3 S spec Silver Sold and gone
Tow bar, full length roof bars, side steps, tow bar storage unit, surround camers.
D4 camera club
24th Jun 2019 3:15 pm
Russell
Member Since: 23 Aug 2007
Location: Kent
Posts: 10564
RRSTDV8 wrote:
Isn't there a scheduling issue with network loads? If one has an EV, charging overnight when the rest of the house is "switched off" would seem sensible. I like the Tesla idea of PV on the roof charging a battery box which is then used to charge the car initially, the rest of the car's battery being filled by overnight network charging.
If people want to run their ovens, power showers, devices, and charge the car at the same time, then there needs to be investment. That will come with bigger bills.
Of course, we need to sort the power source too. Renewables can do a lot - we have a huge wind and tidal potential for an island such as ours. But it needs, you guessed it, major investment.
Have you looked at a Tesla vehicle fire and what is involved. Huge amounts of water are required to put out the fire, 30/40 more times than a standard car and can take 24 hours to fully extinguish and cool before it can be moved. The Tesla then is supposed to go to a secure compoundfor a further 48 hours as there is a tendancy for the to re-ignite.
This causes massive disruption to road networks and water supplies. I guess that the battery storage will be exactly the same and cause further issues and destruction of homes, somthing that has not been thought about or planned forMY17 D5 1st Edition Namib Orange
MY15 D4 HSE Kaikoura Stone
MY12 D4 HSE Nara Bronze Sold and gone
MY11 D4 HSE Stornaway Grey Sold and gone
D3 S spec Silver Sold and gone
Tow bar, full length roof bars, side steps, tow bar storage unit, surround camers.
D4 camera club
24th Jun 2019 4:05 pm
lespes
Member Since: 17 Sep 2009
Location: Sitting Down
Posts: 2232
Probably explains the much higher insurance premiums for an electric car, if they ignite tend to go the whole hog and a write offD4 Landmark MY16 Santorini Black THE LAST
D4 HSE MY12 Marmais Teal: Gone. Missed a lot!
Freelander 2 SD HSE MY11 Silver:Thankfully gone.
D4 HSE MY11 Silver: Gone missed !
Range Rover Sport MY06 HSE Buck Blue: Gone missed!
Discovery D2 TD5 Facelift MY Red Gone Missed!
Discovery D2 TD5 Cobalt Blue: Gone Missed!
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Discovery D1 Avalon Blue First LR! missed!
Now demoted to a VW
24th Jun 2019 4:51 pm
Fitzy73
Member Since: 09 Feb 2014
Location: Truro
Posts: 2407
Russell wrote:
mzplcg wrote:
Well, I know nothing about the national grid, nor the science behind EVs. Neither, IMO, do any of us truly know the impact of human activity on the environment. as a colleague once said to me (a scientist at a pharma company) "It's a very arrogant person who believes that the human race is able to take on Mother Nature and alter her course"
But, answer me this. If EVs are so clean, who accounts for the pollution in generating the electricity? It has to come from somewhere. Renewables are still scarce and also come with an envirnmental impact of manufacturing the kit in the first place.
Who accounts for all the pollution caused by the production of Lithium batteries? Mining, transport, manufacturing and ultimately recycling.
Are EVs any less polluting to manufacture than a petrol or diesel car?
I don't pretend to know the answers but having specific limits to improve air quality in a specific area does seem rather futile to me.
What are some of the biggest polluters, SHIPS and how does all this kit, batteries, wind turbines, EV get moved around the world, by SHIPS!!!!!!!!!!!!!!!
But it isn’t only EVs and other green technology that is moved by ships, it is just about everything we buy.
In terms of building an EV, I have no idea wether they are more or less polluting to manufacture, but supposedly, the factory that built our i3 is sustainably powered, so better than nothing I guess.Andy
24th Jun 2019 4:56 pm
Fitzy73
Member Since: 09 Feb 2014
Location: Truro
Posts: 2407
lespes wrote:
Probably explains the much higher insurance premiums for an electric car, if they ignite tend to go the whole hog and a write off
Our i3 is cheaper to insure than our D4 and only slightly more expensive than the Golf convertible it replaced.Andy
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