Ford Hybrids Not Achieving EPA MPG Ratings: Report

[RaceR]

Originally Posted by serialk11r

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.

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...

[Allch Chcar]

Originally Posted by Justin.b

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

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.

[Justin.b]

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

[rice_classic]

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.

[ZDan]

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?

[serialk11r]

Originally Posted by ZDan

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.

[Allch Chcar]

Originally Posted by Justin.b

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

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

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.

[RaceR]

Originally Posted by rice_classic

3 pages arguing about MPG in the UK and nobody mentioned the Imperial Gallon?![/B]

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

[serialk11r]

Originally Posted by Allch Chcar

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

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.

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

[ZDan]

Originally Posted by serialk11r

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.

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.

[RaceR]

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.

[serialk11r]

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.

[gmookher]

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

[ZDan]

Originally Posted by gmookher

sports cars and efficiency are opposites, needs to stay that way

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.