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

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

#261

Post by joe_the_user »

rnovak wrote: post #247
kbenson wrote: post #235

Earlier quoted context omitted.

It's irrelevant because unless both a) people changed their driving habits on average over that time frame to cause more emissions and b) that change was primarily limited to drivers of GM vehicles, then driver habits do nothing to explain the data. > So drawing the conclusion that manufacturers are "lying" from the discrepancies between those two data sets is ridiculous. Perhaps you should pay attention to actually…

The whole controversy is over manufacturers reporting false numbers, i.e. lying. Saying a manufacturer deserves extra scrutiny can absolutely be inferred to be an accusation of them reporting false numbers, i.e. lying. My reading comprehension isn't at fault here. Secondly, it's still irrelevant. You would have to prove that an improvement at throttle position 0.10 over 5 years equates directly to an improvement at t…

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 position 0.10 over 5 years equates directly to an improvement at throttle position 0.40....

The EPA has essentially said that if this isn't a least somewhat true, the manufacturers are breaking the law.

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

#262

Post by snuxoll »

number_six wrote: post #225
tremon wrote: post #152

Earlier quoted context omitted.

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…

I have a CVT transmission and while I'm sure it is very smart I still feel like I could do better with a manual. I don;t like my car vey much, but it is too practical and cheap to change.

> I have a CVT transmission and while I'm sure it is very smart I still feel like I could do better with a manual. I don;t like my car vey much, but it is too practical and cheap to change.

Is it a actual Continuously Variable Transmission (CVT) or an automatic transmission? There's nothing 'smart' in a CVT since there's gears to shift between, and it's highly unlikely you're going to do 'better' under normal driving since the point of a CVT is to allow the engine to run at ideal RPM's no matter the speed.

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

#263

Post by rnovak »

kbenson wrote: post #259
rnovak wrote: post #247

Earlier quoted context omitted.

The whole controversy is over manufacturers reporting false numbers, i.e. lying. Saying a manufacturer deserves extra scrutiny can absolutely be inferred to be an accusation of them reporting false numbers, i.e. lying. My reading comprehension isn't at fault here. Secondly, it's still irrelevant. You would have to prove that an improvement at throttle position 0.10 over 5 years equates directly to an improvement at t…

> Saying a manufacturer deserves extra scrutiny can absolutely be inferred to be an accusation of them reporting false numbers, i.e. lying. > My reading comprehension isn't at fault here Except that I very clearly said "I can't discount the possibility of something else is going on, such as an influx of a different type of car for GM over that period, I haven't read yet how they normalized the study and accounted for…

> You ignored clear text from me saying that it didn't necessarily indicate GM was at fault. What am I supposed to infer from that?

I didn't ignore anything.

I said the source of data is not irrelevant. That's my entire argument.

And I was specifically refuting your thesis that the source of data is irrelevant.

and, "as to the matter at hand", yes, driver habits can account entirely for the discrepancy in numbers. Flawed data can account for it. Poor sampling can as well.

The report seems to have come from a self reporting site in the EU. Are you asserting that a US car manufacturer has sold a uniform distribution of make/model/engine cars across the globe?

Are you also asserting that this site is getting a proper randomized sample of the car-buying population, such that they don't all have a similar complaint? In my experience, the people who report such things are one of two cases 1) Extremely Satisfied, or the much more common 2) Extremely Dissatisfied.

Are you then also asserting that if GM optimizes for test conditions, which they believe to be similar to normal driving habits, that their engines would be optimized to perform well under conditions that people actually drive in? That's just sloppy. That's like comparing data from your Dev environment to that from Production, I believe there have been a few academic articles to refute that as well.

But, ultimately, are you asserting that we should just accept the source of data as a source of truth, and never question whether or not that it's valid? Should I just go buy a bunch of tabloids and take that as my "new news", since.....the source is irrelevant, right?

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

#264

Post by eveningcoffee »

marze wrote: post #209
eveningcoffee wrote: post #168

Earlier quoted context omitted.

If you read carefully then the report actually does not provide any data about fuel economy. While they speak about fuel consumption and even speculate with numbers, this is not backed up by the data. Report contains only data about CO2 emissions.

Uh, it is the same. Fixed amount of carbon in a gallon of fuel, all will be emitted.

If you assume perfect burning then all carbon burned will turn into CO2. Therefore more CO2 may actually mean more efficient burning and smaller fuel usage (for the same amount of power i.e. less CO, less other particulate matter).

This could happen for example when the engine could not take enough air to burn efficiently (for example because it is stationary).

Unless we have also fuel consumption we could not know which case we are dealing with when we only see CO2 emissions.

For example when the test only measures (and prioritises) CO2 emissions, injection software may decide to use more fuel in inefficient manner to reduce the CO2 emission and then use exhaust filter to capture the extra particulate matter. Well, it is only a wild speculation, but it could be.

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

#265

Post by rconti »

equa wrote: post #88

This is not good, but it is much different from the NOx cheat because consumers can easily measure MPG themselves, and do. For that matter it's commonly noted in car magazines that U.S. EPA MPG ratings are lower the E.U. ratings for the same car & drivetrain; I'm not sure the 50% number in the OP would be so high relative to U.S. tests. It also speaks to the responsibility of the auto press for the NOx issue. They ro…

Yeah, the European cycle has been known to be a joke for quite some time. The US results are actually quite achievable. Their highway cycle max speed is very low (I think it assumes you don't exceed 55mph), but there's so much slowing and accelerating, even on the highway cycle, that you can easily obtain US highway numbers on an open road if you keep it to say 65 or even 70.

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

#267

Post by rconti »

ck2 wrote: post #62

Didn't I read somewhere or maybe it was John Oliver on Last Week Tonight that corporations in the USA report their own MPG to the government on an "honor system" because congress won't fund proper testing by the government. So much for government protecting the people from corporations and their sole quest for profit.

They do, but the EPA also spot tests cars, and the system works pretty well. They recently fined Hyundai for not matching their quoted numbers. The EPA test cycle is not particularly representative of real-world driving, but it's far better than the European tests are, which easily allow you to game the system. Seems like the system works quite well here in the US, even if you might quibble with their idea of a city and highway drive cycle.

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

#268

Post by rconti »

larrys wrote: post #215

Here is one. My Porsche has a display which tells you the MPG. However the car display is consistently between 1 and 2 mpg better than what I calculate after filling the tank and doing the math. And I repeat it's consistently worse than the display which calculates the mgp per tankful which is probably what most people rely on. I've been meaning to bring this up with the dealer but haven't so far. This is in addition…

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.

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

#269

Post by WalterBright »

mturmon wrote: post #249
aianus wrote: post #210

Earlier quoted context omitted.

> Modern cars do better in rolling hills than on perfectly flat land, since they can cut fuel entirely on the downhill This is physically impossible. Even if the car was perfectly efficient at overcoming the force of gravity on the uphill portions (which it is not), you cannot do better than flat terrain (unless by hilly you mean 'net downhill').

I think you should reconsider "physically impossible". Sure, in some idealized situations, the statement you're responding to would be wrong, grievously wrong. But the actual situation has two novel features: (1) the engine uses up power just by being on; (2) you must maintain a minimum speed in order not to block traffic. If you put these constraints in, you can see that it's possible for a pulsed-acceleration strat…

I read years ago that pulsing was the most efficient strategy. Engines have very different efficiencies at different rpms and power settings. The idea with pulsing is to try to operate it at its most efficient rpm and throttle setting, which of course rarely corresponds to the speed over flat ground you'd like to be travelling at. Hence pulsing.

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

#270

Post by rnovak »

joe_the_user wrote: post #261
rnovak wrote: post #247

Earlier quoted context omitted.

The whole controversy is over manufacturers reporting false numbers, i.e. lying. Saying a manufacturer deserves extra scrutiny can absolutely be inferred to be an accusation of them reporting false numbers, i.e. lying. My reading comprehension isn't at fault here. Secondly, it's still irrelevant. You would have to prove that an improvement at throttle position 0.10 over 5 years equates directly to an improvement at t…

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 world reported numbers.

If the EPAs test is completely different from normal driving, then it stands to reason that there is no inherent correlation between manufacturer numbers and reported numbers.

IDK if you've ever been through an emissions test (like the ones GM actually goes through), but they're a complete joke as to simulating real world behavior.

Edit:Format

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