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Discussion Starter · #1 ·
As so many Forum visitors have questions about fuel consumption the following extract from a direct.gov website should be useful: -

The fuel consumption testing scheme gives car buyers the information they need to compare fuel consumption of different models of a similar type. Find out more about the fuel consumption test and what it involves.
Fuel consumption test
The internationally-agreed test is in two parts: urban cycle and extra-urban cycle.

The cars tested have to be run in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.
Urban cycle test explained
The urban test cycle aims to simulate driving conditions in and around town. It is carried out on a rolling road in a laboratory with an ambient temperature of 20 degrees Celsius (°C) to 30°C. The test begins immediately from a cold start, that is, where the engine has not run for several hours. The cycle consists of a series of:

""¢accelerations
""¢steady speeds
""¢decelerations
""¢idling
The maximum speed in the test is 31 miles per hour (mph) or 50 kilometres per hour (km/h), average speed 12 mph (19 km/h) and the distance covered is 2.5 miles (4 kilometres).
Extra-urban cycle test explained
The extra-urban cycle aims to simulate town driving on sections of faster road such as dual carriageways and national speed limit areas. This cycle is conducted immediately following the urban cycle and consists of:

""¢roughly half the test at steady-speed driving
""¢some accelerations
""¢some decelerations
""¢some idling
The maximum speed in the test is 75 mph (120 km/h), average speed is 39 mph (63 km/h) and the distance covered is 4.3 miles (7 kilometres).
Combined fuel consumption figure
The combined fuel consumption figure is the urban and the extra-urban cycle together. It is an average of the two tests, weighted by the distances covered in each one.
 

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Discussion Starter · #4 ·
Almost certainly as would all of the other manufacturers, but I guess it must be done with the normal manufacturing tolerances but always in their favour.
 

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I expect they take 100 cars off the production line, run them in for 20,000 miles or so, chose the best ones for the testand map them for best economy. They put the best tyres on them, narrow width, not the stock OEM ones, slacken off the brakes so they produce minimal drag, put in very low viscosity oil and transmission oil. Probably wrecks the engines, but they don't care. They probably do everything they can to reduce weight, eg put a space saver tyre in. I bet the model they test doesn't even have air con.


Just a few tricks I can think of over a cup of coffee. It's not just Kia that do this of course, they all do.



I'm curious about what they can get away with. For example, take the Rio range. The base model has minimal airbags, no air con, no front fog lights, space saver tyre etc etc, plus 175.14.75 tyres and wheels, whereas the top of the range model has all the kit plus bigger wheels and tyres...however, the quoted mpg is the same fora given engine sizeacross the range. How can this be right?
 

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M4trundler


Don't know about the Rio but the Ceed has different figures depending upon trim/engine spec which makes a difference to the figures. Think the only "mechanical" difference between a 115CRDi 2 and 3 is the tyre size and it makes 1.3mpg difference, OK the 3 has climate and not air con but they don't use it on the tests.



BMW and Ford give exactly the same figures for base with small wheels/tyres and the top model with much larger wheels/tyres but there is always the comment that different wheels and tyres will have an effect. Ford even gave the same figures to a hatch/estate and C-Max variant meaning all the 1.6 TDCi non-eco models had a CO of 119 giving them a £30 tax bill, I wish Kia had done that, would be saving me £60 a year.



From all the makes I looked at last year only Kia, Hyundai and Honda gave different figures that related to the trim grade.



Paul
 

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Here's the link:
http://www.kia.co.uk/New-Cars/Range/Compact/Rio/Specification/Technical-Specification.aspx



Maybe there's something in the small print I've missed - the kind of qualifier you mentioned about trim.



Probably works in my favour as I've gotthe model with all the extras and if the base model is 119g/CO2 (borderline C tax band), mine ispossibly more, ie, pushed into the next band! That is if you can believe the comparison between mpg and CO2. Often you will see a car advertised with a low CO2 figure and yet it will have an mpg value lower than another car with a higher CO2 figure.
 

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M4trundler


The one for the Riois far simpler than the Ceed SW one, see the link http://www.kia.co.uk/New-Cars/Range/Mid-Sized/CeedSW/Specification/Technical-Specification.aspx. The 16" or 17" is the main difference mechanically between a 2 and a 3 and it makes a small but significantdifference.



Found an old Mondeo brochure. Ford state that the figures are all for an Edge model and warn that vehicles with bigger wheels and more kit will do less mpg and emit higher CO but offer no alternative figures therefore people who buy the higher spec cars are getting off light. How do Ford get away with it and other manufacturers give figures for each model.



Think the CO figure is based on the combined mpg thus all cars with the same CO should have the same combined figurebut this may not be exactly the same for petrols and diesels and I cannot be bothered to look.



All manufacturers know the tricks but some do a better job of it than others. As I have said before (I think) our C-Max was a 55 plate Euro 3 (no DPF), before getting the Ceed we looked at getting a new one (old model but Euro 4 with DPF) and the CO had dropped from 127 to 119. Asked the salesman what had been done mechanicallyand he said nothing. A DPF does not reduce CO, in truth during a regen it increases it since extra fuel is burned heating the DPF so how did Ford manage that one? When Kia introduced the phase 2 Ceed the CO's for the hatchdropped from 122 to 119but the engines stayed the same so how did that happen.



Personally I ain't complaining since low CO mean low tax, shame that Kia give the Ceed SW different figures to the hatch though, cost me £60 a year extra.



Paul
 

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Discussion Starter · #9 ·
The all up weight of the car being tested makes a big difference and the manufacturer would have to prove the car being tested was an accurate representation of the model and trim level.


I remember some years ago when my lady friend was buying a small second user car that had seat belts in the back for just two people, whilst the current model had belts forthree the emissions were different and the VED band of the newer car was higher.



KIA are to be congratulated for giving the figures for each and every variant even though many forum subscribers still think the figures are just rubbish.
 

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Would not expect the weight of the car to make any difference on the official test since it takes place in a lab, its long been one of the critisisms of the test. Would suspect that when the car was updated from 2 to 3 belts the manufacturer made many other changes, don't think a seat belt would be noticed on the test. Weighs about the same as a pair of shoes and I ain't driving in bare feet.














If Ford and others declare that the tests are carried out on certain models and state that models with more kit etc will achieve less they are probably covering themselves.



Weight in the real world makes a huge difference and since all new cars get heavier with every update we are paying the penalty in real world fuel consumption yet the official figures remain the same or even improve, all manufactureres are equally guilty.



With regards to weight back in the mid 80's I bought a G o l f GTi, the dogs danglies of hot hatches of its day. It had 112 bhp (less than our Ceed CRDi) and weighed 960kg. 0 to 60 was 8.2 secs and it averaged about 42mpg on my commute. Buy the equivalent today and it will have 200+ bhp weigh 1 1/2 tonnes, 0-60 should be quicker but you would probably be lucky to get 35mpg. Its the way things have progressed, all modern cars have far more safety kit and luxuries butwe pay for them at the pumps as well.



Paul
 

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suttonseven said:
Would not expect the weight of the car to make any difference on the official test since it takes place in a lab, its long been one of the critisisms of the test. Would suspect that when the car was updated from 2 to 3 belts the manufacturer made many other changes, don't think a seat belt would be noticed on the test. Weighs about the same as a pair of shoes and I ain't driving in bare feet.


As I understand it, the test is done on a rolling road. Weight will still increase fuel consumption, since the resistance force on the rollers will be weight x coefficient of friction. Of course, this will be nowhere near as significant as on a real road. I would not expect a single seatbelt to make any significant difference at all, but it's all the little things that add up. Extra electric motors, air con, electric windows, sensors, wiring, extra airbags, extra trim, tools,spare wheel, etc.



Running with hard compound narrow tyres can make a big difference too. One thing they don't do in the test is say whether the air con is on or off.



Kia are not the worst at performance figures. I think in a Which? report they usually reported official figures on averageabout 15% better than actual on the road figures. Many other manufacturers were worse than this.



suttonseven said:
...cars get heavier with every update we are paying the penalty in real world fuel consumption yet the official figures remain the same or even improve, all manufactureres are equally guilty.



With regards to weight back in the mid 80's I bought a G o l f GTi, the dogs danglies of hot hatches of its day. It had 112 bhp (less than our Ceed CRDi) and weighed 960kg. 0 to 60 was 8.2 secs and it averaged about 42mpg on my commute. Buy the equivalent today and it will have 200+ bhp weigh 1 1/2 tonnes, 0-60 should be quicker but you would probably be lucky to get 35mpg. Its the way things have progressed, all modern cars have far more safety kit and luxuries butwe pay for them at the pumps as well.



Paul







Totally agree with you there. I would much rather be in a crash in a modern car than an 80s model, but I can't help feel there is also a lot of unecessary crap that makes cars heavier and heavier.
 

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I did see a documentary a while ago where a university in Canada had a brand new car (small super-mini size) and they stripped it bare, then rebuilt it using carbon composite fibre in place of any steel body work.

The main floor plan, sides, wings, floor pan and bonnet were replaced with carbon fibre.

The result, a 20mpg increase and quicker accelerating car yet it still had all of the usual toys and gadgets.

Not sure what happened after and I am not sure how much a car like that would have cost if it had gone into production but it just shows how much weight today's cars drag around.

Ford (I think) are the only company to reduce the weight of their latest cars (New Fiesta has gone down in weight from 1,130kgs to 970 kgs).
The rival Corsa is now 1,300 kgs, it's just plain silly for a 1.2L engine to drag around.

Edited by: diddy1234
 

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If the rolling road used is a 2wd one the weight/friction increase will only be acting on the front wheels (assuming front wheel drive) thus will only be a fraction of the real world figure.


Official test is carried out with air con off. The Which eqivalenttest is run twice, once with A/C on and once with it off and the mean taken.



What interests me is the fact that the test is carried out on a cold car in a lab that is between 20 and 30 C. If the car has been in the lab for several hours it will not be as cold as a regular cold start in a morning even in summer. Wonder what they mean by "cold".



Don't know where you got the Fiesta weight from, the Ford Brochure I have for a MY10 Fiesta shows the lightest model as the 1.25 petrol at 1041kg. Lighter than the old model but not as light as your figure.



Paul
 

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I stand corrected.

According to parkers the current shape 1.2L Fiesta is 966Kg and the 1.2L Corsa is 1055kg.

Still a lot of weight to haul around for a smaller engine.

I did read some tricks that the car manufacturers use to better their fuel economy tests.

Like for example, where the ecu senses the hand brake is on while driving so changes the fuel map and engine performance.

Or 'Engine software management can be enhanced by
exploiting the safety and durability margins to provide better economy
and/or improved performance'.

The result is nice low emission figures and a fuel economy figure that none of us can achieve.

How would we know, we don't.
i mean are you going to drive around with your hand brake on ?

here's a link to one story :-

http://www.telegraph.co.uk/motoring/news/8368343/Road-testing-under-the-microscope.html
 

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How can manfacturers get better fuel consumption figures by putting the handbrake on, sounds like total nonsense to me. There is only one map in theECU so how can it be changed? Anyway, the tests are carried out by an independant body and not the manufacturer, do they tell the testers to do the test with the handbrake on?


Think Iwould trust Fords own weight figures rather than Parkers, surely Ford know what their cars weigh.



The link you have put on is a totally different matter, nothing to do with the official fuel consumption figures.



Paul
Edited by: suttonseven
 

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I don't think the hand brake thing would be necessary.



There may only be one map in the ECU, but is the road tester really going to download the map and analyse it for tweaks? The manufacturer knows in the lab test it will have lab grade fuel and so will be able to map for tight timings and optimal settings. Plus, it will be a car chosen from the production line that is known to have a good engine and it willbe run in quite a few thousand miles to loosen it up.
 
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