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So what's your site? ... What have you got to lose?

Zakkie links to http://www.carfolio.com/ on his /. profile page. I'm personally completely uninterested in the topic, but it looks like a real site as opposed to a content farm.

He's probably worried about losing his anonymity, knowing that /. is the most likely place on the net to have us all check his whois and reverse DNS records just for fun, etc.

I was commenting on the story, because it impacted me quite directly. Those who wanted to see my site could easily have done what you did :)

So what's your site? ... What have you got to lose?

Zakkie links to http://www.carfolio.com/ on his /. profile page. I'm personally completely uninterested in the topic, but it looks like a real site as opposed to a content farm.

He's probably worried about losing his anonymity, knowing that /. is the most likely place on the net to have us all check his whois and reverse DNS records just for fun, etc.

Are you a (one man) content farm? You're pretty vague about what kind of data you provide.

As it turns out, the World Wide Web (WWW) has these things called "hyperlinks." If you click the GP's name it "hyperlinks" to his profile, which helpfully "hyperlinks" to his website. Neat, huh?

That is how manufacturers measure their fuel consumption numbers, isn't it ?

Yes. The US uses the FTP75 for city, US06 for highway, and a weighted average of the two for combined. Europe uses the NEDC. Japan uses the laughable 10-15.

There is lots of critics here about it, because it doesn't reflects the reality. The numbers are really low, and most users gets their consumption quite higher. Read something about EPA cycle being much more accurate and real.

The US's numbers *used* to be significantly off. They revised the system several years ago to what it is at present, which actually does a very good job. Individuals vary, but if you look at reported averages instead of anecdotes, with the new numbers, it's pretty reflective of average US driving habits. The NEDC is in part lower energy because of typical European driving habits, but it's also dated; Europeans use a bit more energy than it says they do on average today. The NEDC averages about 15% less energy than US combined. The Japanese 10-15 doesn't accurately describe how *anyone* drives ;) It's about 15% less energy than the NEDC. That's why, when hybrids first started coming out, we heard of all of these ridiculous mpg claims for them coming over from Japan (hybrids do exceptionally well on the 10-15).

And yes, I know that it is just a mixture of carbohydrates with very different characteristics.

I assume this is a language issue: hydrocarbons, not carbohydrates. :) Carbohydrates are what you consume when you eat bread, potatoes, pasta, etc.

Citroen C3 1.4HDi diesel versus 1.4i petrol. 2001 models

Diesel ref, petrol ref.

CO2 g/100km: 110 (diesel), 148 (petrol) (34.5% better for diesel)
0-100km/s: 15.4 (diesel), 14.2 (petrol) (8.5% better for petrol)

Scaling the CO2 to account for engine output differences: 26%

That's a pretty exceptional case; normally there's not that much of a difference (the diesel has a turbo and the gasoline doesn't, by the way). For an exceptional case in the other direction:

2011 BMW X5 xDrive35d: 6.4 (0-60), 19 mpg (cty), 26 (hwy), 22 (cmb)
2011 BMW X5 xDrive35i: 0-60: 6.9 (0-60), 17 (cty), 25 (hwy), 20 (cmb)

0-60s from The Car Connection, mpg from fueleconomy.gov. So in this case, the disel is no better than the gasoline *before* adjusting for fuel density, and is worse after. But in general, diesels *are* more efficient. Just not as efficient as your example.

I was using the numbers of standard 320d, not 320dED. ED is lot less powerful (aprox 20hp) and 10kg lighter

I assumed you'd want to compare their most efficient model (*shrug*). All of my comparison figures were for it.

I'm not sure what do you think. Yes engine is smaller, but car is also lot slower.

Not "a lot" slower (at least compared to the model I was doing comparisons with, which is the only one that my above numbers are thus valid for). The thing is, with electric and hybrids, any extra power you add from the electric side, it costs you nothing in terms of efficiency. It can actually improve efficiency. For example, the Tesla Roadster gained about a dozen miles range when it went from Powertrain 1.0 to Powertrain 1.5, a higher power one. It's a totally different paradigm. The gasoline engine needs to only, at a minimum, be able to provide for "average" consumption in "typical" peak operating conditions.

And I forgot another think. Prius don't have gearbox, just clever differential like planet gearing. And I assume this "gearbox" is much lighter then standard transmission.

Another advantage of hybrid tech, yes.

Yes 0-100 numbers are not that different. But in lower speeds the electric engine helps a lot. Once you a

That is how manufacturers measure their fuel consumption numbers, isn't it ?

Yes. The US uses the FTP75 for city, US06 for highway, and a weighted average of the two for combined. Europe uses the NEDC. Japan uses the laughable 10-15.

There is lots of critics here about it, because it doesn't reflects the reality. The numbers are really low, and most users gets their consumption quite higher. Read something about EPA cycle being much more accurate and real.

The US's numbers *used* to be significantly off. They revised the system several years ago to what it is at present, which actually does a very good job. Individuals vary, but if you look at reported averages instead of anecdotes, with the new numbers, it's pretty reflective of average US driving habits. The NEDC is in part lower energy because of typical European driving habits, but it's also dated; Europeans use a bit more energy than it says they do on average today. The NEDC averages about 15% less energy than US combined. The Japanese 10-15 doesn't accurately describe how *anyone* drives ;) It's about 15% less energy than the NEDC. That's why, when hybrids first started coming out, we heard of all of these ridiculous mpg claims for them coming over from Japan (hybrids do exceptionally well on the 10-15).

And yes, I know that it is just a mixture of carbohydrates with very different characteristics.

I assume this is a language issue: hydrocarbons, not carbohydrates. :) Carbohydrates are what you consume when you eat bread, potatoes, pasta, etc.

Citroen C3 1.4HDi diesel versus 1.4i petrol. 2001 models

Diesel ref, petrol ref.

CO2 g/100km: 110 (diesel), 148 (petrol) (34.5% better for diesel)
0-100km/s: 15.4 (diesel), 14.2 (petrol) (8.5% better for petrol)

Scaling the CO2 to account for engine output differences: 26%

That's a pretty exceptional case; normally there's not that much of a difference (the diesel has a turbo and the gasoline doesn't, by the way). For an exceptional case in the other direction:

2011 BMW X5 xDrive35d: 6.4 (0-60), 19 mpg (cty), 26 (hwy), 22 (cmb)
2011 BMW X5 xDrive35i: 0-60: 6.9 (0-60), 17 (cty), 25 (hwy), 20 (cmb)

0-60s from The Car Connection, mpg from fueleconomy.gov. So in this case, the disel is no better than the gasoline *before* adjusting for fuel density, and is worse after. But in general, diesels *are* more efficient. Just not as efficient as your example.

I was using the numbers of standard 320d, not 320dED. ED is lot less powerful (aprox 20hp) and 10kg lighter

I assumed you'd want to compare their most efficient model (*shrug*). All of my comparison figures were for it.

I'm not sure what do you think. Yes engine is smaller, but car is also lot slower.

Not "a lot" slower (at least compared to the model I was doing comparisons with, which is the only one that my above numbers are thus valid for). The thing is, with electric and hybrids, any extra power you add from the electric side, it costs you nothing in terms of efficiency. It can actually improve efficiency. For example, the Tesla Roadster gained about a dozen miles range when it went from Powertrain 1.0 to Powertrain 1.5, a higher power one. It's a totally different paradigm. The gasoline engine needs to only, at a minimum, be able to provide for "average" consumption in "typical" peak operating conditions.

And I forgot another think. Prius don't have gearbox, just clever differential like planet gearing. And I assume this "gearbox" is much lighter then standard transmission.

Another advantage of hybrid tech, yes.

Yes 0-100 numbers are not that different. But in lower speeds the electric engine helps a lot. Once you a

My bad, it is only 44.8%
http://tinyurl.com/39mgjwt

Wrong. Please pay attention to the wording that I highlighted: normal driving. See the highlighting? You're comparing *peak efficiency* to *normal driving*. Check out the graph on the page that you linked. See how much efficiency varies? Beyond that, there's energy thrown away by braking and energy lost to idling. This (very roughly) halves the efficiency in non-hybrids from the peak.

The density of petrol varies around 750kg/m3 diesel around 820kg/m3.
So yes, there is a difference, but it is around 10%

If you had cited Wikipedia, you would have said that they're 18% different, giving a figure of 720kg/m^3 for gasoline and 850kg/m^3 for diesel. But the reality is that neither are right. There is no single density for gasoline or diesel because there is no single fuel called "gasoline" or "diesel". There are all different kinds of blends. They average about 15% difference.

And where the hell the 15% efficiency difference came from ?
I'm quoting your post, using your numbers.

Experience. To be less vague, when you've taken enough gasoline and diesel vehicles of the same model and same acceleration and compared their CO2 outputs and their density-adjusted fuel consumptions, you'll arrive at the same number (give or take ~5%).

For all of the below, I will use this and this for the BMW's stats. I will use this for the 2010 Prius's stats.

And yes, drag areas differs. Prius is smaller. It has also better aerodynamics (0.26 vs 0.27)

I guess I have to explain this one as well. Drag area *includes* the drag coefficient (Cd) (what you refer to as "better aerodynamics"). Drag area is the cross sectional area times the drag coefficient.

Drag areas are what matter, but they're rarely released (automakers prefer to release only the Cd, if that) -- although some release them, and other sites compute them. The BMW 320d EfficientDynamics actually has an official drag area -- 0.59m^2. The Prius does not. So we'll compare dimensions (ignoring length, as length is often a *good* thing).

Width: 68.7"(Prius), 71.5" (BMW)
Height: 58.7" (Prius), 55.4" (BMW)
Ground clearance: 5.5" (Prius), 5.1" (BMW)

If we treat them each as a square, minus the ground clearance, that's 3655 square inches for the Prius and 3,596 square inches for the BMW. So, not taking shape into account, but just dimensions, the BMW actually has a slightly lower cross section. It has a slightly higher drag coefficient. Overall, the drag areas should be approximately equal.

it has low RR eco tires

The Prius comes equipped with Yokohama AVID S33D tires. The BMW uses Michelin EnergySaver tires. Now, rolling drag coefficients are even harder to get than drag areas (and, FYI, are a grossly inaccurate measure anyway). But it's worth mentioning that the EnergySavers are the most efficient tire Michelin makes.

it is front wheel drive so there are (few %) less drive-train losses

True, but the effect is small, as you note.

it is almost 200 kg lighter than bmw (more than 10%)

Prius: 3042 lbs
BMW: 3296 lbs

200 pounds, perhaps, but not kg. Also note that part of the weight of the BMW is due to how heavy diesel engines are compared to gasoline, so this is, at least in part, something that should be credited as an advantage of hybrid tech over diesels, rather than a difference in the comparison vehicles themselves. Batteries are famously heavy, but the Prius pack is very small. Note that aero drag is well dominant in highway cycles over rolling.

it has brake energy