RE: NEDC mpg tests don't lie: Tell Me I'm Wrong
Discussion
Caveated agreement.
I too look at the urban figure as a rough guide as to what I might get from a car, but there are two things to factor in.
1) The same car driven at the same approximate speeds/distances in two locations can get vastly different MPG. In my lumpy bit of the Chilterns I often have to do a few steep hills within the first couple of miles of a cold start, and regularly otherwise. You can imagine the effect this has on overall MPG compared to someone doing trips of the same approximate distances in the Fens.
2) The less 'gamey' the engine the closer you'll get to the NEDC figures. This means the 2.0 TDI that "should" get 75 MPG will of course get nowhere near this unless you drive it like a hearse (and also live in a flat bit of the world), but a petrol snorter like an M5 may claim 25 MPG and you may just get within 4-5 MPG of that, almost regardless of how it is driven (short tarmac abuse sessions excepted).
I too look at the urban figure as a rough guide as to what I might get from a car, but there are two things to factor in.
1) The same car driven at the same approximate speeds/distances in two locations can get vastly different MPG. In my lumpy bit of the Chilterns I often have to do a few steep hills within the first couple of miles of a cold start, and regularly otherwise. You can imagine the effect this has on overall MPG compared to someone doing trips of the same approximate distances in the Fens.
2) The less 'gamey' the engine the closer you'll get to the NEDC figures. This means the 2.0 TDI that "should" get 75 MPG will of course get nowhere near this unless you drive it like a hearse (and also live in a flat bit of the world), but a petrol snorter like an M5 may claim 25 MPG and you may just get within 4-5 MPG of that, almost regardless of how it is driven (short tarmac abuse sessions excepted).
loudlashadjuster said:
2) The less 'gamey' the engine the closer you'll get to the NEDC figures. This means the 2.0 TDI that "should" get 75 MPG will of course get nowhere near this unless you drive it like a hearse (and also live in a flat bit of the world), but a petrol snorter like an M5 may claim 25 MPG and you may just get within 4-5 MPG of that, almost regardless of how it is driven (short tarmac abuse sessions excepted).
Surely a 25 mpg car getting within 5 mpg of its official figure, is the same as a 75 mpg car getting within 15 mpg?The elephant in the room being of course just how far removed from the real world the test cycle really is.
Engines should be tested under heavy load or gradiants, ideally with the car loaded with 2 passengers plus a healthy amount of ballast.
You will probably find small capacity turbo engines all of a sudden become a hell of a lot less desireable when reality kicks in.
Engines should be tested under heavy load or gradiants, ideally with the car loaded with 2 passengers plus a healthy amount of ballast.
You will probably find small capacity turbo engines all of a sudden become a hell of a lot less desireable when reality kicks in.
Bladedancer said:
I mean lets be serious. How car a over 1.7 tonne 5 meter car with 3 liter 272bhp diesel do over 50mpg combined? Magic?
Sure, because such a car is using all 270hp all of the time in all driving conditions.Funnily enough, the 3.0l diesel will need roughly the same amount of power to maintain 30 / 40 / 50 / 60 / 70mph as a car with a 2.0l engine. Or a 4.0l engine. But all of them will be doing it more or less efficiently than the other.
The difference is that if you HAVE 270hp then you might use it some of the time which will harm fuel economy. That is outside the realms of the test cycle though
there is nothing wrong with the NEDC cycle, or testing in laboratory conditions. However the testing could be made more realistic! (read closer MPG figures to those achieved by the majority) this would involve changing the test cycle and the test conditions as is proposed for next level of emissions testing EU6c or EU6.2 as it is sometime called. (there have already been some slight mods for EU6a & EU6b) as the changes aren't yet set it stone this will hopefully include a WLTP cycle (a much more transient driving cycle) this would be closer to real driving and if this had been adopted some years ago we probably wouldn't have any vehicles with auto stop/start technology as it wouldn't provide a benefit on a WLTP cycle. I'm getting slightly off topic. there could also be changes to the battery charge at the start of the test. this would address the ludicrous figures reported by hybrid vehicles. and finally (I'll get my soap box soon) the test could start at a more realistic temperature. 20 to 25 deg C is not a realistic start temperature. i believe 5 to 10 Deg C is what i think is proposed.
Agreed. I think the majority of people only really care how it hits their bank balance.
I also think that if they managed to cheat the tests, the spotlight should be on those whom set the test and the policy makers who have approved it to resign, as much as it should be the manufacturer who fathomed the dodge.
The fact there is a test in use which seems almost entirely useless, is the real problem.
I also think that if they managed to cheat the tests, the spotlight should be on those whom set the test and the policy makers who have approved it to resign, as much as it should be the manufacturer who fathomed the dodge.
The fact there is a test in use which seems almost entirely useless, is the real problem.
mwstewart said:
The tests don't like: you aren't wrong. The problem is the tests aren't representative, but to say that a scientific, repeatable, consistent, test couldn't be set up to get somewhere near real-use reality is just plain wrong IMO.
I agree with this. If tests were more realistic, engineers would spend far more useful time trying to create actual economy rather than theoretical, and if someone was going to offer you 10% off your actual fuel bill each year for the same performance, of course you would take it.Also, it would be great to get rid of stop-start. When riding into the city centre, it is not only noticeable but it islaughable how long it takes modern cars to get away from the lights. Ironically this leads to bigger tailbacks at each set of lights and more pollution from those cars (still the majority it seems) that don't have the technology as they sit there waiting.
Article said:
Because hand on heart, anyone who really cares about what comes out of a car's exhaust pipe wouldn't drive a car. Who honestly selects a vehicle on its mpg or CO2 rating out of a desire to save the planet?
For some of us it was important because the CO2 determined the VED. MPG is also important to some of us. I've been known to stretch the budget to fit a car I wanted in the past but its very hard to justify a car that does 20mpg against another that does 30mpg when trying to get it past the other half - especially when you know damned well the 30mpg one won't do 30mpg but thats all the other half sees.
I now have two cars on the drive that average around 32mpg between them. One does a regular 45mpg or more (Smart Roadster) and the other does a regular 20-25mpg (SL500).
The other half never queried the second car as it was something I wanted and which she knew would not be used daily. If I had tried to replace the Roadster with the SL there would have been rebellion.
So MPG is important to some of us that don't have unlimited finances to spend on cars (we spend our cash on holidays and a second home is the current priority).
ChasW said:
This is what was good about the old Autocar tests. They had two real-life MPG figures, test and touring, which provided a more useful guide.
Agree with this - it was simple and effective. So, how to update/adapt the old Autocar tests into 21st Century thinking with regard to emissions while keeping the process simple (because I've always admired the old engineering adage "Elegance Through Simplicity")?Well, if it were possible to design and build some kind of 'emissions capture' device to be attached to a test car in the manner of the old "Fifth Wheel" (which Autocar probably pioneered way back when) then it might also be possible to measure the total emissions put out by said test car over the same two old Autocar criteria - ie. 'steady speed figures' and 'overall figure for total test mileage'.
This 'capture device' would need to be able to analyse the key emissions (NOX and CO2 would suffice, I'm guessing) in order to lay out a compact series of criteria (NOX at x MPH, CO2 at x MPH, NOX overall over a given mileage, CO2 overall over a given mileage).
Once a basic comparison template is thus established (again, hopefully 'keeping it simple') then the list of cars tested, together with their fuel consumption and emissions results) would allow the majority of non-technically minded people to understand where the test results were coming from and hopefully give a clear and simple picture of what a prospective purchaser could expect in real-world driving conditions.
The beauty of the old Autocar tests were that they were free of government interference and their particular 'wishlist' at any given time for foisting loaded facts, figures and , in some cases, pure fiction (!), on us depending on their socio-political 'take' at any given time.
Sorry for not keeping my language 'elegant through simplicity' (!) but I'm fed up being led by the nose (in many walks of life) by governments and other well-intentioned but sometimes ignorant official bodies who ALL have their own agenda (whoops, I'm off on one!).
If the key motoring publications (I assume Autocar, What Car etc) could 'steal' the initiative here then we might be afforded some decent, unbiased criteria which would be for the good of all.
Anyway, just a thought (or two).....!
I don't believe the NEDC have any strict guidelines on how a vehicle is tested, e.g. a car manufacturer can hand over a vehicle with tyres over inflated for better rolling resistance etc. little tricks like that to further bump up official claims. It's not illegal to do it cause it's not enforced, no law.
The VW software "trick" however, was and is a big issue in Merica, the fact that any software like that exists in a vehicle is against their laws and not so much EU. An unlike the EU whom don't give a s
t about their people and encouraged the sales of diseasels, Merica are very strict about the N0X that's emitted from these cancermobiles.
And don't forget how much politics has to do with this anyway, Merkel with "her" Economy and the VAG group trying to become No. 1 in sales, conquering Merica with it's "ultra clean green" diseasel technology was a must, too bad they were caught out, EU market needs growth, it's fecked now and if UK leave it altogether there's no hope (politics)!!
The VW software "trick" however, was and is a big issue in Merica, the fact that any software like that exists in a vehicle is against their laws and not so much EU. An unlike the EU whom don't give a s
t about their people and encouraged the sales of diseasels, Merica are very strict about the N0X that's emitted from these cancermobiles.And don't forget how much politics has to do with this anyway, Merkel with "her" Economy and the VAG group trying to become No. 1 in sales, conquering Merica with it's "ultra clean green" diseasel technology was a must, too bad they were caught out, EU market needs growth, it's fecked now and if UK leave it altogether there's no hope (politics)!!
jezzaaa said:
I agree with you re the lab testing and the need for consistency to make the results valid. But I think the advertised figures being so far away from real-world is a massive problem, for punters and dealers alike.
Only to people who clearly live under a rock and don't do their research properly.How do you think the same punters are going to react when a new test gives :shock mode: higher CO2 results :shock mode off: and their new shiny car is going to cost more to tax?
As for dealers, do you think they will have no problems with results produced from a new test, for example, how do you think a salesman is going to explain why the punters new Audi A1 TDI has worse CO2 emissions and lower fuel economy than the their 3 year old model that has come to the end of its PCP? Because just saying, "Ah well, it's the new NEDC test you see" just isn't going to cut it, they don't understand the current NEDC, so they sure as hell won't understand why the new one makes the cars performance worse on paper than their old car just because of "a test"
Some very interesting/good points in this one.
What strikes me is that from a VED point of view, we're penalising the vehicle, not the way in which it is used.
VED targets CO2 emissions, rightly or wrongly. The NEDC tests are just the manufacturers' way of cooking the books to make their vehicles more appealing to those who either actually care or can't afford not to care.
But what's the difference in emissions between a 999c triple city car being driven 13k a year and a 5.7l C3 Stingray that comes out twice a year if it's sunny enough?
The VED system as it stands penalises the Stingray.
Similarly, what of the V8 petrol Discovery mk1 which is driven 5k a year on school runs versus a Mondeo TDCI that does 30k a year?
The best solution in my eyes is to scrap VED and increase the duty on fuel.
It then becomes a Pay-as-you-go system, which rewards careful consumers of fuel and taxes the heavy users. Drive your car hard and you pay to do so.
Spend the funds reserved for ANPR traps on dip-testing diesels to check they're not using "pink" , and give the haulage industry any necessary tax relief to ensure they're not worse off.
Surely the best benefits are through behavioural change, not penalising choice based on an arbitrary system?
What strikes me is that from a VED point of view, we're penalising the vehicle, not the way in which it is used.
VED targets CO2 emissions, rightly or wrongly. The NEDC tests are just the manufacturers' way of cooking the books to make their vehicles more appealing to those who either actually care or can't afford not to care.
But what's the difference in emissions between a 999c triple city car being driven 13k a year and a 5.7l C3 Stingray that comes out twice a year if it's sunny enough?
The VED system as it stands penalises the Stingray.
Similarly, what of the V8 petrol Discovery mk1 which is driven 5k a year on school runs versus a Mondeo TDCI that does 30k a year?
The best solution in my eyes is to scrap VED and increase the duty on fuel.
It then becomes a Pay-as-you-go system, which rewards careful consumers of fuel and taxes the heavy users. Drive your car hard and you pay to do so.
Spend the funds reserved for ANPR traps on dip-testing diesels to check they're not using "pink" , and give the haulage industry any necessary tax relief to ensure they're not worse off.
Surely the best benefits are through behavioural change, not penalising choice based on an arbitrary system?
Edited by Evilex on Wednesday 21st October 12:02
Whatcar is pushing with 'true world' MPG
Regularly publish test numbers
http://www.whatcar.com/truempg/my-true-mpg
Regularly publish test numbers
http://www.whatcar.com/truempg/my-true-mpg
TooMany2cvs said:
Fetchez la vache said:
If we're going to get / our taxes are all enviro-bks it would seem something should be added to include the real through life environmental cost of all cars including creation and disposal.
Hmm. Not easy to calculate. Do you hit a new car buyer with a retrospective tax if they write it off, so the life was much shorter than expected?ks it would seem something should be added to include the real through life environmental cost of all cars including creation and disposal. dukebox9reg said:
Whatcar is pushing with 'true world' MPG
Regularly publish test numbers
http://www.whatcar.com/truempg/my-true-mpg
That would be lovely if they covered more cars. They barely cover any petrol versions, it's diesels as far as the eye can see with a very occasional petrol thrown in.Regularly publish test numbers
http://www.whatcar.com/truempg/my-true-mpg
I hope no-one here is measuring their car's MPG via the on-board computer, and only using brim-to-brim calculations.
My family wagon's claimed combined mpg is 47.9.
The on board computer, reset when I bought it, after 27,000 miles is showing avg of 49.8mpg
I record brim-to-brim amounts and mileages via a spreadsheet and the real average is 46.3mpg.
My family wagon's claimed combined mpg is 47.9.
The on board computer, reset when I bought it, after 27,000 miles is showing avg of 49.8mpg
I record brim-to-brim amounts and mileages via a spreadsheet and the real average is 46.3mpg.
Fastdruid said:
I disagree. Having a real world test would mean manufacturers could concentrate on tuning for real world conditions rather than a tiny fraction of that.
The offshoot could be a *real* improvement rather than an on paper improvement.
^^ This, in buckets.The offshoot could be a *real* improvement rather than an on paper improvement.
There is no need to change the concept of a standardised test performed on a dyno with real world resistances applied. What needs to change is the test cycle. If you make it resemble how cars are actually used, optimising the cars for the cycle will also optimise them for the real world. If you don't, there's no guarantee of that. If you don't test what matters, the test becomes what matters.
T0MMY said:
Not sure about that! Not everyone is a petrol head.
I know numerous environmentally conscious people who would quite like to not drive at all but have to as it's the only viable form of transport for them. MPG and emissions are very important to them.
So do I. Some people genuinely care about this stuff.I know numerous environmentally conscious people who would quite like to not drive at all but have to as it's the only viable form of transport for them. MPG and emissions are very important to them.
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