How can they improve the fuel economy of the next generation Pruis?

I noticed you compared different cars with different engines and with different mileage which makes any comparison of emissions useless since mileage, amount of fuel burned per mile, is the main determinant of emissions.

A 60 mpg Diesel Prius would likely have better emissions than a 50 mpg gas Prius.

Regarding emissions, using CO2.

A Diesel Golf gets 30% better mileage (a 65 mpg Prius) while producing 14% less CO2.

A 65 mpg, 14% less CO2 Prius would be a sweet ride.

 

CO2 emissions are directly related to fuel consumpsion (1 l petrol = 2.33 kg CO2, 1 l diesel = 2.64 kg CO2):
60 mpg diesel car would have 103 g/km
50 mpg petrol car has 110 g/km
a 53 MPG petrol car has same CO2 emisions as 60 MPG diesel car

I think that with $ 2.000 premium you can easily make petrol Prius to get 53 MPG

 

A Google search says diesel has 13.5% more heat energy per volume than petrol, so a 50 mpg Prius emits about 5.75% more CO2 per distance than a 60 MPG diesel.

Other than PS, anybody else feel like spending $10,000 USD for the privilege ? I say $10k, but the current diesel-hybrid that costs $10k more than a current Prius in the UK emits more CO2 per distance.

 

You can't or don't want to get it. Those figures are averages. Have you ever heard about the properties of the average? It's a good estimation of the expected value. So comparing - for example - fuel economy averages is the best way to compare different cars even driven in different circumstances (the more sample data the more accurate estimation).

Diesel Prius never existed and never will, hence this assumption is totally pointless.

 

Not on short urban commutes. Particulate filters clog up.

 

Just to your point, where do these wild ideas of much better diesel fuel economy come from. Here we have the popular ford focus and vw jetta tdi

Compare Side-by-Side
The diesel gets combined 34, the turbo charged direct injected gasoline 33. Both companies went to make these vehicles efficient. Hybrid tech jumps up much more, with a heavier car the c-max getting 47mpg, 17 in the city more than the diesel. YMMV, but diesel is not going to get you 20% in america, pollution control is going to sap some of that extra grunt. I don't see how popping that vw diesel in the prius would get you 60mpg unless many other things happened.

I would look at it this way, diesel tech on a gasoline engine less than $1000 extra - egr, direct injection, turbo charging. Full hybrid $3000. Diesel more than $2000. Going full hybrid diesel would add over $5000 and the fuel savings might be 10%. The big diesel advantage is efficiency at low load, but the hsd runs at high loads.

That is why vw is going a flywheel hybrid - less expensive than hsd along with putting the diesel tech in a gasoline engine. jetta hybrid with gasoline should do 45 mpg combined, 30% better than the jetta diesel. If they had hsd, they might do that instead, but they don't. Either way vw says diesel is just too expensive right now for too little gain in a hybrid. Either way vw would likely pair a turbo to the hybrid instead of atkinson, but I expect toyota to stay normally aspirated. Toyota said in the lab they have only gotten turbo charging in the lab a little more efficient than normal aspiration.

 

Base Prius model costs 111 000 PLN (33 433 USD), while base Yaris Hybrid costs 66 100 PLN (19 909 USD). 23% tax included.

 

How about a non-Hybrid Base Yaris?

Here the 5 door Yaris Automatic is MSRP $16K and the Prius Two is MSRP $25K.

That's $9K for about 15MPG.

 

Totally base Yaris costs 43 900 PLN (13 222 USD) but is much less equipped than Hybrid (no rear-view camera, no air conditioning - even manual, no graphical LCD, no DRLs) and is a 3-door car with 1.0 engine. Hybrid is only available as 5 door.
Comparable version of Yaris is:
Yaris 100 5-door SOL - 54 400 PLN
Multidrive S CVT - 5 000 PLN
Cool package (dual zone A/C) - 1 300 PLN
It gives total: 60 700 PLN (18 283 USD), which means 5 400 PLN (1 626 USD) difference for similiar equipped car with different engine only.
Toyota Motor Poland calculated that lower fuel consumption, lower service costs should sum up to 18 000 PLN (5 420 USD) over 5 years / 100 000km (62 500 miles) of hybrid warranty period. I think that at least half of this is possible to reach.

 

For what it's worth, MB claims the diesel-hybrid version of its E-class produces 26% lower CO2 emissions (23% lower life-cycle) than the straight diesel version (E 300 BlueTEC Hybrid Awarded Environmental Certificate | Hybrid Cars).

Regarding emissions, upstream ("well-to-pump") emissions need to be included in my opinion. Assuming the 60 mpg for a diesel-hybrid version of the Prius is valid, WTP emissions would be as follows based on EPA emission factors:


WTP emissions @ 50 mpg gas (G); 60 mpg diesel (D)...

VOC - 0.114 g/mi (G); 0.016 g/mi (D)
NOx - 0.084 g/mi (G); 0.074 g/mi (D)
CO - 0.028 g/mi (G); 0/025 g/mi (D)
PM2.5 - 0.009 g/mi (G); 0.008 g/mi (D)
SOx - 0.044 g/mi (G); 0.039 g/mi (D)


Also, according to a 2004 Toyota report (http://www.mizuho-ir.co.jp/english/knowledge/report/pdf/wtwghg041130.pdf, Table 2.1.3, page 19), the following is a calculation of upstream CO2e emissions...


12.19 g CO2e/MJ (gasoline); 7.88 g CO2e/MJ (ULSD)
121.89 MJ/gal (gasoline); 134.38 MJ/gal (diesel)
12.19 g CO2e/MJ – 7.88 g CO2/MJ = 4.31 g CO2e/MJ more for gasoline
12.19 g/MJ X 121.89 MJ/gal = 1485.8 g CO2e/gal (gasoline)
7.88 g CO2e/MJ X 134.38 MJ/gal = 1058.9 g CO2e/gal (ULSD)
1485.8 – 1058.9 = 426.9 g CO2e/gal more for gasoline
Per EPA, 8,788 g CO2/gal (gasoline); 10,084 g CO2/gal (diesel)
8788 g/gal + 1485.8 g/gal = 10,274 g WTW CO2 emissions/gal (gasoline)
10,084 g/gal + 1059 g/gal = 11,143 g WTW CO2 emissions/gal (diesel)
11143 ÷ 10274 = 1.085 = 8.5% more CO2e/gal for diesel WTW


Hopefully, the calculations are correct.

 

This (by EPA) 34 mpg Golf Diesel ?

Using 13.54% more heat content/volume of diesel, the Golf has
(((50*1.1354)/34)-1)*100 = ~ 70% more CO2 emissions/distance than a Prius.

You wouldn't be comparing the NEDC test and imperial gallons to EPA and US gallons again, would you ?

 

www.fueleconomy.gov lists mileage and CO2 emissions and lets you compare cars side by side. The 30% better mileage and 13% better CO2 emissions of the Golf Diesel would indicate that a Diesel Prius should get the same 30% mileage boost and 13% decrease in CO2.

 

Funny how people who have an almost religious bias against Diesels will say anything. We had one person claim a Diesel could do not the auto/on/off of a gas engine...I mean really silly stuff. Now we have that the VW, Audi, Merc Diesels can't do urban commutes or their filters will clog.

 

Oh, I see.
You compared a diesel Golf to a petrol Golf, and jump to the conclusion that the same advantage should be seen in a Prius hybrid that uses a diesel ICE instead.

BAD REASONING.

Here are two of the more obvious reasons you cannot make that jump;
1. The ICE in the Prius is not the ICE in the Golf
2. The drivetrain (HSD) in the Prius is not the same as the drivetrain in the Golf

 

US Department of Transportation. FuelEconomy.gov which does nice side by side comparisons of vehicles. If you compare the VW Golf gas/auto with the VW Golf Diesel/auto you get 30% better fuel economy for the Diesel and 13% lower CO2 emissions for the Diesel.

 

NO

He said reliability of the filters suffers if the car is mostly used for short trips. You should quote what you are responding to so that others can see you are mangling posts to fit your trolling.

Fwiw, I spent some time on a diesel forum not too long ago to read about this question. It seems to be common knowledge that short trips do not heat up the exhaust system enough to purge the filter, and over time leads to filter failure.

 

Yes...silly stuff like that. So back to facts per Fuel Economy with Diesels showing 30% better fuel economy and 14% better CO2 emissions, that would be just the kind of boost in performance we'd hope to see in a 2015 Prius.

 

You are still confusing the mythical Otto cycle Prius with the Atkinson cycle Prius.

 

I'm using the US Dept. of Transportation FuelEconomy.gov stats showing Diesel vs. gas comparison in identical cars (VW Golfs) with Diesel providing 30% better fuel economy and 14% better CO2 emissions.

 

...I sort of like Prox's ardent support of a petroleum product...even if it is diesel...actually let's face it we have all wondered if a diesel hybrid makes as much sense as a Prius...maybe not, but I am sure we'd buy it if it gave us 70 MPG. I think it is a valid plank on the Walter Lee's nice list but more in the R&D (speculative) category.