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Discussion Starter #1 (Edited)
Campaign group Transport & Environment says carmakers exploit loopholes in EU law to achieve favourable but unrealistic miles/gallon results.

They suggest the official fuel consumption cited by car manufacturers is on average almost 25% lower than that achieved in reality, and in some cases 50% lower.

The EU commission's consultants believe that 30% to 50% of the drop in claimed CO2 emissions between 2002 and 2010 "does not result from technology".

Article is here

Full report is here

Interestingly,the tricks manufacturers use are listed as including:
- disconnecting the alternator
- overinflating tyres
- taping over gaps in the bodywork and sealing the radiator grille
- using special low friction lubricants
- wheel alignment to minimze rolling resistance
- testing at altitude (low air resistance)
- using higher gears
- testing at unrealistically high temperatures
- using super slippery test track surfaces
- using a rolling road and misprogramming it for a lighter car
- Moving brake pads away from disks (not braking during the test)
- Deliberatedly under-reporting CO2 results by 4%
- Deliberatedly exploiting the testing tolerances (under speed, longer stops)

Also worth pointing out that the manufacturers do not make their raw data public either...

The upshort appears to be that much, perhaps most, of the improvement in EU car fuel economy and emissions over recent years is fictional, and that current models probably perform very little better than their (often smaller, lighter) predecessors!
 

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I think the discrepancy has less to do with car makers fiddling the tests and more to do with the test being hopelessly unrepresentative of real-world driving.

Have you seen the NEDC test cycle?



That's done on a rolling road, in a lab at a 20°-30°C starting temperature - and hybrids can start with a full SOC. No lights, heater, aircon etc.

Edit: IMO the best way to tax CO2 is not via a test cycle like this. They should reduce or abolish VED and stick the tax on fuel.
 

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Hard to believe this would happen in another country than the USA.

Yeah, Ive said from my own use of a prius how its larger battery at a full soc can easily ace those tests where as the Honda its harder to do so.
 

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Every model of Insight 2 pretty much aced the NEDC. They all got 60+ mpgUK on the urban cycle, which, as you can see from the graph, is repeated stop and go.

In mpgUS, that's around 10mpgUS over the EPA urban rating.

I see the EPA ratings as achievable for most drivers, given a bit of concentration. NEDC is pretty much useless for anything apart from comparing numbers from different cars.

Another reason for NEDC bring unrealistic is it has no constant velocity testing at speed. You only go above 70mph very briefly during the test. This has led to many small engined diesels getting much worse numbers than their NEDC extra urban on a motorway trip. Larger engined diesels would tend to pull in some great numbers on the motorway, relatively untroubled by hills and speed.

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Mpg

I read that the fuel consumption is not actually measured directly in the test, the exhaust emmissions are measured and the fuel consumption "estimated" from those measurements.
 

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Its on a rolling road aswell with declared CdA values for the car aswell as other parameters. The car doesnt move and hence the comments about taping the gaps is just ridiculous untruths.

The tests are completed by an independant laboratory with a computer controlled 'throttle' robot
 

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Some also program the ECUs to recognise when they're driving an EU test cycle and when they're not. (dual fuel/ignition tables - one for on test and one for real world) Also used to cheat drive-by noise and so forth.
 

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Discussion Starter #8
Some also program the ECUs to recognise when they're driving an EU test cycle and when they're not
Good grief - that's plain unethical.

It's clear that the public are getting very sceptical about big MPG claims. When we're asked about the car, we've had to *show* some people the dash display and point at the "86.1" (or whatever) to underline that this car actually does what we say it does!
 

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There is also no requirement for trip computers or speedometers to be accurate.

Speedos are allowed to display (100%) to (110% + 6.25 mph) of your actual speed.

Most high end cars display your actual speed if the tyres are unworn, less 2 mph. Cheap cars (and the 'bubble' shaped nissan micra is the worst for this) show 110% plus 6.25 mph.

An indicated 70 mph is actually only 58 mph and an indicated 60 mph is actually only 49 mph - this is part of the reason that there are lots of outraged grandmas cruising in the inside lane of motorways and causing a danger to other road users at "60 mph" (49 mph) in their miserable little cars whilst tut-tutting at these outrageously fast lorries.

Roadworks too. The average speed through a 50 mph roadworks (as measured by the police averaging cameras) is just 40 mph. Why? These muppets driving miserable little cars with speedos that lie. If you drive at an actual 50 mph, (nevermind 55 mph!) you *fly* past all the traffic.

Ditto driving at an *actual* 80 mph (which would be an indicated 95 mph in a late 90s Nissan Micra if it ever got there...) it's rare to be passed unless you're on the M40 or M50.

Where am I going with this? Your odometer lies too. Says you've gone further than you actually have. So the trip computer lies to the customer. Deliberately.

Fuel pumps at the forecourt also have a tolerance that's non-trivial, and you can bet your bottom dollar that they'll be set to favour the forecourt. ;-)

You know what the core problem is though? People who buy new cars either:
-are simly too stupid to do the sums on fuel economy (only about 20% of the population is numerate remember)
-can do the sums on fuel economy and give absolutely not one hoot because depreciation, insurance cost, or company vehicle taxation dominate the operating cost of a nearly new vehicle (you'd need £5/litre to change this)

But yes. Unethical. Can't say I shed too many tears for the type of moron who buys a brand new little french diesel car 'because it is cheap to run' - they're clearly quite well off and would save more money running a 10 year old 1.6 focus into the ground. Fool Money. Easily parted. ;-)
 

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Even if the EU law was strictly enforced, the NEDC needs a major overhaul.

The cycle is completely unrealistic for most drivers, even before manufacturers start gaming the system. Doesn't help that the test uses warm ambient temperatures, uses no electrical accessories and has no steady speed highway element. It's utterly moronic how the test results are tied to VED and congestion charging in the UK too.

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