Diesels emit 14.4% more CO2 per gallon, which partially offsets their mpg advantage. I think that was the point. Europe apparently goes by CO2/km rather than mpg (er, L/100km).

As far as the hybrid gasoline vs. non-hybrid diesel argument, for equivalent price and performance cars, the diesel would likely have a slight edge in fuel mileage on the highway, probably no advantage in CO2 emissions. They hybrid would still have a huge advantage in city driving.

Personally, I'd prefer hybrid gasoline to diesel. I would hate to see diesels get as popular in the US as they are in Europe, where at every fuel pump at the gas station you have to stand on surfaces soaked in diesel fuel (the stuff doesn't evaporate). Yuck.
Also morally against engines that don't rev above 5500rpm :P

Why don't they have diesel hybrids? Seems that a diesel Prius could make some Hwy mpg gains.

Diesels cost more money than gas engines, hybrids cost more money than non-hybrids, diesel + hybrid would be more expensive than diesel or gas-hybrid, and way more than a gasoline non-hybrid of similar size/performance. You'd get kick-ass mileage, but the price would be a problem.

What components of a diesel engine make them more expensive to manufacture?

Is it an economy of scale thing, where they're more expensive to produce because the manufacturers are producing fewer of them? Is there a component or a few components that are essentially different from their petrol counterparts and raise the price?

-Justin

Injection system is quite different.

But we're not using only volume. We're using the volume of fuel per miles driven. Using those two factors, it's simple to compare different fuels. Energy content isn't even a factor and either is price. If I go 70 miles on one gallon of gasoline and I go 70 miles on one gallon of diesel, then that's a direct comparison that is completely relevant. If someone wants to make the argument that one fuel costs more than another or one fuel has more energy content than another, then that's a different argument. But to say that going 70 miles per gallon of fuel A is different than going 70 miles per gallon of fuel B is just ridiculous.

Premium and Regular also have the same energy content. There's been a movement in Europe to use Liters per 100 km which makes more sense as MPG reaches the point of diminishing returns. The difference between 40 MPG and 50 MPG is only 1/2 gallon more to go 100 miles, 2.5 gallons vs 2 gallons, respectively. Meanwhile the difference between 20-25MPG is 1 more gallon per 100 miles, 5 gallons vs 4 gallons respectively.

We're not just using one liquid fuel anymore though and manufacturers are having to explain different levels of fuel economy using the shitty MPGGE (Miles Per Gallon of Gasoline Equivalent) which is ridiculous. Think about it, the Leaf gets 98 MPGe but it can't even go 98 miles! And it's not ridiculous to recognize that there is a significant difference between Gasoline and Diesel. Ignoring that fact is just being ignorant.

The EPA doesn't even test most vehicles. They don't have the budget to do it. They just take the manufactures estimates and use them.

For some of the crying about the media in this thread, its good to see manufacturers called on BS'ing these numbers. It's the only thing that is going to make the EPA go back and actually test the car to see if the OEM is cheating or not.

I don't care about diesel....it doesn't have any relevance in my life. And the quote below is an ignorant statement, because 70mpg is 70 mpg, it doesn't matter which fuels you're talking about. Sorry that you can't grasp that simple concept.

Originally Posted by serialk11r http://www.ft86club.com/forums/third...s/viewpost.gif
Diesel fuel has higher energy per unit volume anyways, so 70mpg is not the same as 70mpg on gasoline.

Im with white shadow here..

MPG is MPG.. If we are not talking in a context where economy, CO2, NOx, "energy density", etc are factors its really simple.You put a gallon of some liquid in a tank and you meassure how many miles you get... No need to make it harder than it is.

In EU we use l/km. But lately with the growing focus on CO2 per km that is a number that is more used on paper when looking at new cars.

EU target for the average new car is 85g CO2 per km in 2020.
In a diesel engine that would be 73.33 MPG
In a petrol engine that would be 64.19 MPG

Thanks! That + diesel prices (vs petrol) in US really explains why petrol is the preferred choice.

But when looking at US emissions on petrol engines I certainly don't consider them strict. People on this forum consider the FR-S to be fuel efficient. In EU its considered bad.

Its also important to not only measure EU based on overall "standards". Because in many cases its up to each country how they adjust taxes.. (several countries does not have extra taxes on cars) In Norway CO2 taxes on the GT86 is 12500 USD (which is only 1 out of 4 type of registration taxes on top of 25% VAT). In comparison, a car with 110g CO2 would get zero CO2 taxes. And a car with 90g CO2 would get -2800 USD in taxes (would still be a lot of registration taxes in total).
That is strict!

Having 35000 USD in taxes on a GT86 and only like 3600 on a VW UP!.
That is stict!

Many of the typical cars in the US have so high emission outputs that they would never sell here. But than again, our tax system in Norway is quite stupid.. But also quite effective to get emissions down..

We're talking about technology and efficiency though. Diesel engine getting 70 mpg does not mean it's as efficient as gas engine getting 70mpg. That was the point. Not so hard to understand. Diesel you get more range, but gasoline you just use a bigger fuel tank. Gasoline is lighter anyways.

So traditionally the components all have to be stronger to withstand the higher pressures and higher specific torque, and there's no option to use cheap port injection. By bringing compression ratio down manufacturers are making them cheaper to build, but emissions equipment is making up for any cost saving many times over, just ask any diesel pickup owner.

Typical European opinion...emissions is not the same as fuel efficiency. Your cars are more fuel efficient, but they put more toxins/pollutants into the air. CO2 emissions is just a fancy word for fuel economy. The FRS puts out less toxic emissions per mile than most of the cars sold over there, even as it's burning more fuel.

150mg NOx/km is kind of a joke, sorry. Let's put that in perspective. If your car is emitting 150g CO2/km, 150mg NOx is 150ppm (in a gasoline engine). http://www.clubxb.com/forums/showthread.php?t=44856
This guy's car is not in the best shape, he is emitting over 100ppm NOx, well below what the EU says a brand new car in 2012 is allowed to emit from the factory. The average tested NOx emissions for his car is just 16ppm, and smog tests are only required on 4 year and older vehicles so no car rolling into a test center is as clean as it was from the factory. Of course, the smog test is a bit different from the actual certification, where they run the engine under higher loads at times which increases emissions. This is clearly just to accomodate your giant diesel fleet, everyone else has stricter NOx standards, and the US has the strictest by far. We pay for that in the form of reduced fuel economy and power.

The European standard is still expressed in distance per volume. They just made the distance a constant. If you want to break out the calculator, you can easily convert between the two units.

What you're saying is that it's better to express my height in centimeters instead of feet because then my height will be a bigger number so I'll be taller.

-Justin

One of the big differences (and I would guess this varies by country) is taxes and other penalties based on engine displacement. There are no restrictions on that over here.

A teenager can get his license and drive off in a 5000 pound SUV with a 6.2l V8 the same day. Our licensing is also a joke - which makes that teen even a bit more scary.

The 86 doesn't get great gas mileage. It's just that it's acceptable mileage for the fun the car delivers. You can drive it like a complete idiot and still get 20mpg, which isn't terrible. A lot of sporty cars fall WAY short of their estimated mileage when you start giving them the boot.

-Justin

Thanks for clarifying some with your post..

Do you have some numbers for the part I quoted?
Besides NOx, what do you consider toxic emissions that is worth to make notice of. How would you rate the importance of them compared to CO2 and NOx?

The only number I have on new cars are CO2 and NOx. (181g per km and 16mg per km for GT86. I assume US numbers are basically the same)
I would consider CO2 to be bad and NOx is better than the average car when looking at GT86.
But then again.. NOx levels are really up and down here.. Mostly in the 10-40mg per km range as far as I have seen.
M135I with manual is rated at 13mg of NOx per km, which is low.
M135I with automatic is rated at 161mg of NOx. Which is insanely high!

I think you'd have to ask a toxicology specialist or something like that to get a well informed view on how bad NOx emissions are for public health and whatever. In the US the regulators seem to think NOx is the end of the world, whereas in Japan they don't care as much. I'm not convinced that losing 5-10% fuel economy is worth cutting NOx down this much, but maybe there are some health studies that suggest otherwise.

In my opinion NOx in the US is overemphasized because a pre-emissions-regulated diesel puts out far far more NOx than any gasoline engine, and semi trucks consume a huge proportion of our transportation fuel and surely spit out much many many times more NOx than all the gasoline cars combined, though these trucks don't drive in heavily populated areas as much as passenger cars do. Still, one semi truck rolling down the freeway probably is putting out the NOx that a hundred gasoline cars puts out, so how different is it if gasoline cars are allowed to use 20:1 AFR lean burn and emit 5 times more NOx? I see a lot of diesel trucks on the road.

NOx is the toughest toxic emission to take care of because you need a perfect stoichiometric mix to ensure the catalyst is not being "poisoned" by oxygen.

I am also not convinced that CO2 emissions in themselves are important, but I think that fuel efficiency is an important matter. The way cars are rated in the US for fuel efficiency is really stupid, I don't know how the EU system works so I can't comment on that. I also can't comment on the discrepancies in the example you gave.

You seem to be well informed on the subject in general at least. :)

In Norway the higher focus on CO2 made the sales of diesel cars "explode" some years ago. 4/5 out of 5 new cars sold cars ran on diesel. In recent years the air quality in the two larges cities have gotten much higher NOx levels (More diesel cars in combination with more people driving and generally more traffic) That becomes a problem in the winter. There have been many discussion about what to do about it. Even discussions about banning diesel cars from two of the "large" cities when NOx levels are at its highest. NOx is difinitlely a concern, but government are too slow to change taxes into the right direction. Seems like there is a shift towards petrol again now..

Dont know how EU and US fuel ratings compare. But I know many cars use around 10% more than claimed. There is talk about a better system in 2020, but im not into any details...

You're close, the actual height is still the same but now the numbers are more accurate. Eg. instead of saying I'm 5' 11" and being "close enough" I could say 182 cm and be more accurate. Which is pretty accurate. The higher we go with fuel efficiency the less important each MPG is so the greater need to be more accurate. Now being off 2-3 MPG is not a big deal but it's possible in the future than a small error would mean 5-10 MPG.

If I AM exactly 5' 11" tall, then converting that measurement to another unit doesn't add any accuracy.

In any case, we're a nation that doesn't yet understand the meter. I wouldn't expect to see quick adoption of a new unit of measure.

-Justin

3 pages arguing about MPG in the UK and nobody mentioned the Imperial Gallon?!

The UK uses the Imperial Gallon which is essentially 25% larger than the US Gallon. Thus any of these awesome MPG figures you're seeing in cars from the UK, just knock off 25% and that's the USA equivalent.

There's a lot of hype of how efficient diesels are because often we hear of these diesels in Europe getting incredible mileage (like on shows like Top Gear for example) but folks forget to "do the math". Diesels are efficient and make great torque (which results in low rpms and cars with longer gears) and good mileage. The USA VW Jetta TDI averaged something like 40-45mpg on the freeway on the US gallon with a diesel. That's pretty groovy for full size sedan with torque.

Imperial gallon is 20% bigger than US, not 25%. And to correct UK mpg, you wouldn't knock it down by that percentage, you knock it down by a factor of (1/1.2) = .833, or -16.7%.

I don't know if earlier posts were referring to imperial gallons, but RaceR's post on page 2 specifically refers to US mpg. The crazy mileage figures he and others have reported of course have zero to do with real-world mileage, though!

Regarding diesels and torque, turbocharge a gasoline engine and it will have a ton of torque, too. 2.0 TDI makes 236 lb-ft, 2.3 turbo in the Mazdaspeed3 makes 280. 236*2.3/2.0 = 271, so in this case the gasoline engine is making more torque per liter.

One reason diesels are tall-geared because they *have* to be, they simply can't rev as high as gasoline engines. Another is that turbo diesel cars tend to be designed for maximum mileage. Of course the tall gearing negates a lot of the mythical torque advantage.

I wonder what a tall-geared, low-revving turboed 2.0 gasoline engine, designed/engineered for maximum mileage, would get for mileage vs. a 2.0 TDI in the same car? No doubt, the diesel should get better mileage, as there's ~15% more energy per volume in diesel. Would it get better enough mileage to have lower CO2/mile emissions?

Yea you make good points, the tall diesel gearing is because they simply have pathetic peak power and rev range, so they need taller gears by default.

For a low rev turbo 2.0 gas engine with clever valvetrain, look no further than the BMW N20. Though maybe worse gas mileage than 2.0 TDI equipped cars, the gas mileage is still fantastic, and the engine has 250hp+ whereas the TDI has less horsepower than my 1.8L long stroke low rev Corolla motor in some trims. If they made it a 1.5L and reduced the boost, they could still match the highest powered 2.0 TDI for power and the engine would probably weigh half as much, and the fuel economy numbers might be even higher.

We can't all be blessed with your good fortune. :rolleyes:

The metric system is on it's way here. I learned it in elementary school and I use it now and then, when I can. Plus it's 10x easier than the English system. :D

All my numbers/post was converted to US MPG.
As far as I know (I may be wrong). All EU countries except UK uses kilometers and liters.
Cars are usually measured in L/100km.

I use this site for converting numbers.
http://www.unitjuggler.com/convert-f...km-to-mpg.html

What about those horse powerz? :P

74.57 kW/L doesn't sound as cool as 100 horsepower /L. Maybe the standard will go up to 100kW/L :D

The BMW's rwd invokes an efficiency penalty of ~4% due to ring/pinion (changing power output 90 degrees = inherently lossy). Of course IMO it's MORE than worth it for rwd! But even at the same weight, the BMW would have an efficiency disadvantage.

There is going to be turbo 1.5 liter gasoline turbo hybrid Jetta. With 30 more hp total than the TDI, it's supposed to get 45mpg combined, 32% better than the TDI. CO2/mile should be 2/3 that of the TDI.

Turbodiesel vs. turbo gasoline hybrid fuel mileage, in the same car => hybrid wins, BIG time.

It would be interesting if they made a non-hybrid version at 140hp, that would give a direct comparison between diesel and gasoline.

US vs EU fuel efficiency numbers - paper rating comparison
 

US BMW 328I Sedan/manual 23 /34 mpg (24/36mpg automatic)
US: CO2?? , NOx??

EU BMW 328I Sedan/manual 8,5 Urban/5,1 Extra-urban/6,4 combined L/100km
EU:149g CO2 and 23mg NOx per km (Automatic is @ 147g CO2 and 12mg NOx per km)
-149g CO2 per km equals 6,4l/100km. So EU g CO2 per km is the combined fuel number.

-EU l/100km converted into US MPG: 27.67 Urban/46,12 Extra-urban/36.75 combined
(EU numbers converted into US MPG for the automatic version:29/46/37)

I did not find the US NOx number, so that is one factor that could make US milage worse (if tuned for lower NOx and higher CO2). But seems like EU numbers generally are higher (in terms of MPG).

If anyone have US NOx numbers, please share.

EU fuel mileage ratings seem to be higher generally, yes.

I think the thing with diesel vs. gasoline is that especially in the absence of emissions controls, diesel engines have acceptable heat release rate and high expansion/compression ratio. Because they do not have to premix the fuel, the low rpm efficiency is a bit better (but gas engines with low lift cams or TGVs or something make this better) since there are no combustion stability issues. Diesel engines have lower specific output, so they need a higher displacement to be useful, and at higher displacement they are more efficient at lower speeds, but passenger diesels aren't necessarily bigger.

On the downside, they have higher frictional losses because they depend on high pressure and temperature to ignite the fuel, and they have lower heat release rates than gasoline engines.

Toyota thinks they can get over 40% thermal efficiency using direct injection + Atkinson cycle + EGR. If they allowed lean burn at 1.1 lambda the way big diesel engines are essentially not emissions regulated, I suspect they could bring that up maybe 5% more, and 42% thermal efficiency is actually better than a lot of diesels. If they used a bigger engine say a 2.5L 4 cylinder, I bet they could bump that up to 43%.

The diesel cycle in theory is worse than the Otto cycle (you can consider the "Atkinson cycle" version of both too), but in practice it's been able to do better since combustion is harder to control with premixed charge and spark ignition, and even if they could burn very lean it's hard to ignite a premixed ultra-lean fuel mixture.

I think that if someone really wanted to, they could build a "diesel style" gas engine with NOx trap, extremely long stroke, higher than usual compression ratio, stratified charge direct injection (along with port injectors) enabling very lean mixes, and say a 2 stage variable duration cam for different load ranges, both low lift, they could end up with a gas engine that has a rev limit below 6000rpm, works great down to 700rpm or something stupid low like that, and low fuel consumption. What would happen is that it would end up costing just as much as a diesel (probably more than a diesel actually) and have crap specific power just like a diesel.

sports cars and efficiency are opposites, needs to stay that way
look what power you get from an efficient subaru? I'd have spent more money with the dealer if they offered a more powerful motor, screw MPG

For me, sports cars should be, above all, small and LIGHTWEIGHT. For reasonably-priced real-world sports cars, add zero-lift/zero-downforce and minimum drag. Should add up to great fuel efficiency.

For several years the highest measured fuel economy in the back of Road & Track magazine was the 1st-gen Lotus Elise, at 35mpg.

True sports cars should be reasonably fuel-efficient.

Oversized/overwrought/overweight sportified luxobarges weighing over 3300 lb. and touted as "sports cars" should be replaced by smaller, more minimalist TRUE sports cars.

http://i1.kym-cdn.com/photos/images/...Suspicious.png

http://www.astonmartinw.com/wp-conte...artin-dbs2.jpg

Exactly, a supercharged Lotus Elise is no slouch by any measure and can sip fuel almost as conservatively as a Prius if need be. A lot of effort is going towards developing effective regenerative braking, but people tend to forget that at 40% wheel to storage to wheel efficiency or lower, a 2 ton luxobarge hybrid is still wasting more energy on deceleration than a typical compact car.

Maybe the Elise is a bit of an extreme car, but a couple of carpets, some trim, and even an airbag or two is not that heavy in the grand scheme of things.

Take the Elise, put in a 2ZZ or 4AG like supercharged engine with modern combustion chamber/fuel delivery and friction/parasitic load reduction, give it an extra gear and some aerodynamic tweaks, it'll literally be as fast as some supercars (top speed will be somewhat lower of course) while getting Prius fuel economy numbers. Heck, MR2 Spyders with Europe spec gearboxes can get almost 40mpg mixed without any tricks, and that's with a 15 year old engine.

That's why I said UK, not EU. Thus the Imperial Gallon. And I wasn't calling you out specifically fyi, or anyone for that matter just pointing out a common and glaring misconception about reported MPG ratings.

Anyone who's ever watched Top Gear or Fifth Gear or any British car show for that matter, knows that I'm on about.

Oh God I hope not!!

The best sports cars for me have been the efficient ones. Efficient use of materials for saving weight, efficient use of technology to reduce pollution, efficient use of engine tech to improve daily driving while still delivering performance on track (Vtec, VVTI etc). Not to mention the other developments in efficiency that improved sports cars like: improved brake compounds, improved efficiency in lubricants for better protection, longer change intervals and less lubrication and improvement in efficient suspension designs just to name a few... The list goes on and on and on about how Sports cars have only become as good as they are because of a focus on improving effeciency.

As for fuel economy

I find it myopic that these two ideas must be held separate. In fact, so does every race car engineer. The whole point in building a more competitive car is building a more efficient car, from power to aero to weight. Colin Chapman would definitely disagree as well as would every engineer up and down the 24 of LeMans grid, especially the developers of the Delta Wing.

Why are people in the Supercharger threads asking about a clutched compressor? So they can still retain OEM MPG efficiency for daily driving. The demand for power and efficiency is out there, so why wouldn't supply be?

Ask and S2000 owner they wouldn't mind a taller 6th gear for better fuel economy...

I think the idea of holding efficiency and sporting as two competing and exclusive thoughts is like saying, one should only be attracted to women are either Hot or Smart but not both because that would be ridiculous. Well it isn't ridiculous, it's awesome. Just as having a fun sports car that can still get terrific mileage is awesome.

Have you looked at the SkyActive D yet? They developed the lowest compression diesel for any production car to date so the engine will rev higher and perform like a petrol engine in regards to sportiness and power delivery while still providing the efficiency of a diesel. Uh, yes please.

:thanks:

On a different note, I tipped this story to AutoBlog, Carscoop, and Motor Authority and none of they chose to post it on their sites.

Silence! :bellyroll: Kilowatts sounds way cooler than horsepower even though the number is lower. Unless you're a fan of horses. :P

Autoblog has now covered it but without any credit given for the tip.
http://www.autoblog.com/2012/12/06/c...x-h/#continued

Hopefully it gets looked into.