Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Study: Some car models consuming around 50% more fuel than official results

transportenvironment.org

Post reply on HN
Print view View original

291–300 of 336 posts

Re: Study: Some car models consuming around 50% more fuel than official results

#291

Post by JonFish85 »

TheCoelacanth wrote: post #233
JonFish85 wrote: post #177

Earlier quoted context omitted.

One way or another, regular folks will pay for it. If it's directly by paying this tax, that's straight forward. Otherwise, the company will take the hit, and the cost will flow towards stock-holders, which in general tend to be unions, 401k plans and such. How much of your 401k are you willing to lose due to that cost? How much of your parents' 401k/union pensions is OK to forfeit?

That sounds like an argument for never punishing corporations for anything, which is clearly unworkable. Pension and 401k plans are typically diversified across a broad range of stocks, so they won't be heavily impacted by a single company's stock price dropping. On the other hand, executives and board members, who are actually responsible for the company's actions, will typically have a large amount of that company'…

That's not how I meant it, but I can see how that's a fair reading of what I said. I don't like that people jump onto ideas very quickly without thinking through the ramifications. I don't think a lot of people realize how wide-reaching effects from quick knee-jerk reactions can be, and how much they can actually have effects beyond the first-order ones.

Re: Study: Some car models consuming around 50% more fuel than official results

#292

Post by eveningcoffee »

MagnumOpus wrote: post #241
eveningcoffee wrote: post #185

Earlier quoted context omitted.

The thing is that this report does actually not provide any data about fuel consumption - only about CO2 emissions. What they do is wild speculation and possibly a smear campaign because people care more about the fuel economy (their own money) than CO2 emissions. It is interesting that this (some) data is provided but how it is presented does not make it look very credible.

What are you on about? For any given type of fuel, fuel consumption is related exactly 1:1 proportionately to CO2 emission (as carbon particulate and CO emissions are microscopically small these days). That is basic chemistry - where else would the fuel go? Therefore any claim about CO2 emissions equates to a claim about fuel consumption.

Yes, it should be.

The problem is that these findings do not reflect my anecdotal experience.

I have two recent measurements. About 500 km round trip and small trips inside the city.

This is accordingly about 17% and 21% increase (and it was in the same region for the older model of the same car).

Sorry, I did not include the make and model of the car because I do not want to leak too much personal information but it is nowhere close to the claimed difference.

Even more the round trip was mostly on the highway and included small city part (let say about 20 km). This differs from the official test cycle.

Also the city traffic includes high elevation differences and very bad slow traffic with constant stopping.

Also the car was more occupied in both cases (official tests consider about 70 kg driver and 7 kg luggage).

This means that in more fair test the results should be even more close to the official numbers.

So what could explain this?

I do not know as we do not see the fuel economy numbers.

Perhaps during the official tests the car is actually stationary and can not take enough air and the burning is not that efficient but a good exhaust filter hides this problem?

What is also strange is the difference between BMW 3rd series and 5th series because both use the same engines (and also some Renault models do use BMW engines but it do not know about Megane).

I calculated the fuel consumption and CO2 ratio for several models and it is about the same (as expected).

I also calculated weight to CO2 ratio for similar engines over few series and this gave also very similar results. As the different series look quite similar these days then I would assume that they also have quite similar aerodynamics.

Re: Study: Some car models consuming around 50% more fuel than official results

#293

Post by rconti »

ptaipale wrote: post #279
rconti wrote: post #268

Earlier quoted context omitted.

Yeah, mileage computers in cars are known for being a bit optimistic. It's not hard to beat the EPA highway number for your car. Put it on the highway, cruise at 65mph, done. The EPA test cycle doesn't even exceed 55mph, but it has quite a bit of slowing and speeding up, so you can beat it with a consistent cruise a good bit over their 55mph number.

A partial reason for this is that the speedometers have to be optimistic by law (depending on jurisdiction, but I think this is the case most everywhere. When your speedometer shows 100 km/h, it is permitted that true speed is 90 km/h, but it is not permitted that the true speed is 101 km/h. And the same variance applies to odometer, of course. Things like tyre wear and pressure have a noticeable impact on what both…

This is true -- my understanding is that Germany actually requires they never read low EVEN IF FITTED WITH THE WRONG SIZE TIRES which is sort of insane.

That said, I believe the odometers are typically bang on, which would mean the mileage calculation should be accurate. Or could be, if they wanted it to be.

Re: Study: Some car models consuming around 50% more fuel than official results

#294

Post by semi-extrinsic »

rnovak wrote: post #270
joe_the_user wrote: post #261

Earlier quoted context omitted.

The whole controversy is over manufacturers reporting false numbers, i.e. lying. No, actually it isn't. The controversy is over manufacturers tuning their vehicles' engine behavior to give economy for the tests and for the tests only. By your criteria, that's not a problem but VW has already been bitten really hard by the revelation that they did this. ...You would have to prove that an improvement at throttle positi…

I'm not sure what your definition of alter is, but for me to alter means to lie . They weren't simply optimizing for test conditions, they were outright lying during test conditions. that's what the EPA is saying is against the law. Here's the thing, and this is my main point: If the EPAs test conditions reflected normal driving habits, there would be zero difference between Manufacturer reported numbers and real wor…

So I threw together a histogram [1] of car CO2 emissions as reported by manufacturers for 1200+ model/engine combos. It's not exactly uniformly distributed, to say the least, there is a strong peak at 99 g/km etc. Now that's maybe not conclusive evidence that they are lying, but it's certainly suspicious.

[1] http://asmunder.github.io/2015/09/A-histogram-of-CO2-emissio...

Re: Study: Some car models consuming around 50% more fuel than official results

#295

Post by mzs »

zardo wrote: post #231
awjr wrote: post #107

Ok let's be real here, if we put the "pollution" taxes onto fuel and not on the design of the car, this problem, in effect, goes away. There is still the issue that high efficiency, usually means running the engine at high temperatures which generates far more NOx gases. We should be taxing the amount of fuel used.

That works for CO2, because there is no technology to mitigate CO2 release from combustion. But that isn't the case for particulate matter, carbon monoxide, or nitrogen oxides. You can't put a NOx tax on diesel because the amount of NOx you produce from burning a given quantity of diesel will vary by two orders of magnitude depending on the pollution controls.

Just one clarification, CO2 recapture is a thing, for example in coal power plants built after 2014 in US. But yeah for car, really impractical.

Re: Study: Some car models consuming around 50% more fuel than official results

#296

Post by briantrice »

mikeash wrote: post #204
cLeEOGPw wrote: post #65

Earlier quoted context omitted.

> except electric Why? You have just been shown corporate cheat on tests. Why you would ever assume this has something to do with fuel type? I expect Tesla cheat as much as MB or BMW in their "range" test. And if you believe otherwise you are just someone who doesn't learn from his experience.

Tesla's range numbers for the Model S assume about 300Wh/mile average consumption. My average consumption so far over not quite 8,000 miles is 315Wh/mile. It's hard to cheat in an electric car. Few people care about efficiency directly, but most electric car drivers care deeply about range , and range is just battery capacity multiplied by efficiency. If Tesla were cheating so they could lie about efficiency, Tesla o…

I have definitely found that electric vehicle companies advertise very sound and realistic figures for their mileage.

My personal case is a Zero motorcycle, but I've heard confirmation from owners of other kinds; the range it gets is more or less exactly what they state for the test conditions (straight level ground, no winds, etc etc). Mine did in fact improve when I adjusted the aerodynamics, but that's another topic.

Re: Study: Some car models consuming around 50% more fuel than official results

#297

Post by happyscrappy »

zardo wrote: post #226
happyscrappy wrote: post #85

Earlier quoted context omitted.

Actually the VWs that were emitting 40x pollution in the US were only 10x of the Euro regs.

Eu has stricter PM limits, the US has stricter NOx limits.

http://www.hybridcars.com/will-america-avoid-europes-clean-d...

Re: Study: Some car models consuming around 50% more fuel than official results

#298

Post by mzs »

andor wrote: post #148

Carmakers, not drivers, are the cause of the problem as obsolete official test results are being manipulated. Then why does this report compare NEDC numbers with user-submitted real-world consumption? Since car manufacturers have increased power output while keeping NEDC consumption relatively constant, rather than the other way around, you need to drive very carefully to get close to the official numbers. It should…

Thank you for the link. I was hoping it would include more detail about the cars. For example which engines and do they have start-stop. About the only thing I saw mentioned but not well accounted for was the automatic gearbox difference.

I have a car with 2.5L turbo engine and I can get from 13.5-28MPG from a tank of gas depending on a number of factors, mainly on how I drive, but also what fuel, how loaded-up the car is, and tires. I suspect that automatics with turbo or supercharged engines with start-stop have the greatest difference in real world v test performance. And yes that is because of how people drive compared to the test.

Re: Study: Some car models consuming around 50% more fuel than official results

#299

Post by rconti »

tremon wrote: post #152
Zelphyr wrote: post #102

Earlier quoted context omitted.

Care to share some of those tips?

This is by no means an exhaustive list, nor an authoritative one. Would love to hear other's thoughts on these: - When accelerating, try not to over-extend the throttle. If the engine is at 2k rpm, you get just as much acceleration from 30% throttle as 100%, at half the fuel cost. - Release the throttle well before you reach a traffic light/stop sign. Deceleration by engine will cause a smoother stop and gives the tr…

> - When accelerating, try not to over-extend the throttle. If the engine is at 2k rpm, you get just as much acceleration from 30% throttle as 100%, at half the fuel cost.

Well, that's obviously not true.

Re: Study: Some car models consuming around 50% more fuel than official results

#300

Post by Theodores »

nkurz wrote: post #273
Theodores wrote: post #232

Earlier quoted context omitted.

I cannot imagine a cyclist imagining this to be true! Obviously aerodynamics play a part, however the cyclist's 'engine is cut' on the downhill and on big cross country roads no brakes need be used on the descents. When the 'engine' is on it goes at a certain not-quite-racing amount whether up hill or on the flat. But place a hill in the way of A to B and vastly more 'fuel' is used than A to B 'going the flat way'.

Consider a different visualization: what if instead of a hill, you were crossing a valley? Starting at the top of the hill, you coast down and make it most of the way up the other side. Are you certain this will take more energy than pedaling the whole way across the flat? What if you can start by coasting 90% of the distance with zero expenditure of energy? What if it was 95%? Now assume that your chain is extremely…

Even a rusty chain is ridiculously efficient - in the high 90%'s. An ICE and drive chain is pitiful in comparison, so let's substitute the chain for a missing rear axle nut so that, when pedalling, the wheel pulls to one side and creates tangible frictional losses.

I grew up in a very hilly area plus I have done a few continental rides where hills can be graded nicely and go on for 10 - 20 miles with little change of gradient. The hope to coast up the other side of the valley never really works out as well as one might hope, with a road that goes down a big hill you are invariably pedalling on the lower reaches of the down hill part, even if you were doing a good 30+ mph at the top. This can be due to the valley heating during the day giving a prevailing headwind due to air expanding.

Meanwhile, in the steep hills I grew up in, you can get a measured 40+ mph, conservative guessing (I would be boasting if I mentioned top measured speeds as they can be quite incredible but 40 mph is the town limits speed and it is cool to exceed it on a bike). Clearly this speed scrubs off with aerodynamics not being favourable. So you really do not blissfully roll up the other side, roller-coaster style.

On a daily basis I go over an arched bridge that does have a hill leading in to it. So you can coast down the hill, up over the arch and on down the other side. The fun is to not pedal over the bridge, to be in 'roller-coaster' mode. This feels good, and easy, but there is a psychological factor going on here. One's brain is distracted by the 'roller coaster' (or traffic) and not really noticing how much of a slog things are.

Essentially the only way things could work out anywhere near how you imagine is if there is no atmosphere. The cost of speed is aero and you just do not get the free ride up the other side of the valley, period.

If it was quicker/more efficient to go up and down hills we wouldn't have land speed records be they by bicycle or rocket car set on dead-flat courses, would we?

With the sibling reply regarding undulating paths, that is part 'mind trick' as it is mentally stimulating going up and down like that. It is just an illusion...

However, I can in part rescue your line of thinking on this - muscle groups... I actually like hills and you can use your arms, legs and plenty of muscles in between to 'conquer' a hill. On the flat you are more likely to just spin (unless sprinting). Maybe if you factor in the baseline power your body needs for pumping blood around, maybe that could make things 'possible'.

But the more I think about it - no... Look at motorways and trucks. Trucks are more efficient than cars even if they have lots of wheels and no obvious aerodynamic considerations. Lorry drivers do not choose the undulating 'A road next to the motorway when one is available. They stay on the motorway doing their most efficient speed (as that is how to make a profit). Hills that any car or lorry could go up are cut through with motorways, to make things as flat as possible.

Post reply on HN