Non-hybrid cars that give Good Fuel Economy (highway)

The 2014 BMW 328d (diesel) technically meets the emission requirements for SULEV based on official CARB certification data (even though it's "only" certified ULEV). Evaporative emissions are a non-issue with diesel, a requirement for PZEV. PZEV has an extended useful life of 150,000 miles (120,000 miles for SULEV), but doing a linear extrapolation of the emissions deterioration from 50,000 miles to 120,000 miles, the 328d would still meet the PZEV emission standards out to 150,000 miles.

PZEV will be going away as an emissions category with full implementation of LEV III anyway. SULEV20 will be the new lowest emission category, and the 328d would meet even that based on the linear extrapolation previously mentioned.

 

The catch is, shutting of the engine while driving like a hybrid does, compromises the emissions. Those diesel systems depend on it running all the time. Many currently also require exhuast treatment, like urea spray. That's not the case for any gas hybrid.

Also, keep in mind that going from 120,000 miles to 150,000 miles cannot be extrapolated. Those extra 30,000 miles must be accomplished with a dirty & aged emission system. That's why reducing sulfur has been so important.

 

If I'm not mistaken, the 328d has stop/start?

 

Believe so. The Audi 3.0 TDI has it too.

 

There's a huge difference between being capable and actually delivering.

Cost is a major deterrent.

 

Since the low fuel demands of idling are when lean fuel mixes will be common, a start/stop system likely improve a diesels emissions.

 

Cost is the reason many makes, including Toyota, certify vehicles for more polluting bins in federal states.

 

Except that the only diesel I can find that you've said significantly beats the Prius for highway fuel economy is the new gen Polo 1.2 TDI Bluemotion. Which beats it primarily by being smaller, lighter, and slower rather than necessarily more efficient. VW does claim 2.8L/100km highway in their press release, but the UK/VCA extra-urban rating is 3.1L/100km. Still impressive, and better than both the Prius's 3.9L/100km and the more appropriately sized Yaris hybrid's 3.5L/100km. That gives the Polo about 11% better fuel economy (at least for highway) than the Yaris hybrid, but essentially the same btu efficiency / carbon efficiency / cost per mile (again highway only). And that's still with the Yaris Hybrid being significantly quicker to 100km/h (11.8s vs. 13.9s), indicating surplus power / additional potential opportunity for improvement in highway efficiency if that was the design optimization goal. If the Polo had a hybrid drive system added, it might at least make up the substantial gap in city fuel consumption (4.2 vs. 3.1L/100kM) making the two vehicles about equivalent on an overall combined (not just highway) fuel cost, carbon output, and btu efficiency basis. Of course the Polo TDI already costs the same as the Yaris hybrid, so one would assume there would be some additional upfront cost associated with adding the hybrid system to it.

So once again, it seems to me that what on the surface might look like indicators of the potential advantage of a hybrid diesel when analyzed just show once again how the Toyota HSD/Atkinson system has already claimed most if not all of the efficiency gains that might be expected from switching to a diesel engine.

We'll really never know until some one builds an actual production model, but I just don't see the evidence for the great improvement so many expect from a hybrid diesel.

Rob

 

Isn't the Peugeot 3008 hybrid more powerful, bigger, and more efficient than a Prius? Seems like there are still gains to be had.

Cars such as the Civic 1.6 i-DTEC or Golf 1.6 TDI Bluemotion Technology are 3.3L/100km on the extra-urban cycle and actually even beat the Prius on combined mpg as well. And looks like they are about £2k cheaper too. Maybe a hybrid drive system could improve the urban consumption and push the overall mpg even higher.

 

Just how are you getting to this estimate?

I hope it doesn't come from wrongfully comparing car models cars offering diesel vs. old-fashioned Otto-cycle gasoline powertrains.

 

Thanks for pointing out the 3008, definitely need to read up on that one!

 

A single test load condition on a laboratory test stand doesn't transport me from my source to my destination. I need a legal passenger car working over a whole driving trip cycle, experiencing many different load conditions.

The quote to which I responded appeared to much more broadly compare diesel vs. gasoline, then used the Beetle as an example. But that gasoline Beetle is hindered by an old technology gasoline powertrain, not a newer technology gasoline system such as found in Prius and numerous other modern vehicles.

Your diesel-gasoline comparison should have explicitly stated that is was excluding the best gasoline systems on the market.

But 94 g-CO2/km is not better than a number of gasoline non-Honda vehicles in the same market.

 

Ok, so here's a first look at the info I can find on the Peugeot 3008 diesel hybrid.

First reaction, looks kind of amazing on paper. Looks similar in size to Prius v, acceleration looks impressive, claimed mileage seem pretty phenomenal for size / weight. Only downside I see is price, at 27-28k quid, its about 6k quid more than a Prius, and about 8k quid more than the non-hybrid 3008 diesel. Reviews mostly seem to say its pretty good, but hard to justify at the price. I've also yet to find a review that got better than an average of mid-40s mpg Imp, which a number of them noted was the about same they got on the non-hybrid 1.6L diesel 3008.

From UK/VCA for 3008 (Prius Prius+)
Urban Cold: 3.1L/100km (3.9L/100km 3.8L/100km)
Extra Urban: 3.6L/100km (3.7L/100km 4.2L/100km)
Combined: 3.4L/100km (3.9L/100km 4.1L/100km)
C02: 88gm/km (89gm/km 96gm/km))

So far looks pretty good. Similar on highway (better than +/v), considerably better in city, lower combined consumption, similar combined CO2 output. Not bad considering it is bigger than the Prius, more like Prius+ and quicker than either. I am a little puzzled by the Prius's urban rating on the VCA though. Seems a bit fishy that its worse than extra-urban, and worse than Prius+ (v) Urban.

Interestingly, the Argonne National Labs got hold of a 3008 diesel hybrid to test on US Driving Cycles. Since they have also tested the Gen 3 Prius on the same cycles, we can do a pretty good direct compare. The only confusing variable is they seemed to determine that the manufacturer supplied rolling and aero loads were optimistic, so there are two set of numbers.

Cycle: 3008 Manf Loads (3008 ARL Est Loads) 2010 Prius
Urban (UDDS) Cold Start: 53mpg (Not Provided) 63mpg
Urban (UDDS) Hot Start: 59mpg (49mpg) 70mpg
Highway: 65mpg (53mpg) 67mpg
US06: 40mpg (36mpg) 44mpg

For one reason or another, the 3008 seems to fare much worse relative to the Prius on the US driving cycles. For urban, 19-43% higher fuel consumption depending on whose load numbers you use, Highway similar to 26% higher consumption, US06 10-22% higher consumption. Even if we assign at 10% penalty to the Prius numbers to approximate the Prius v, the 3008 still wouldn't look that great. Granted this is still not really an apples to apples comparison, the 3008 is effectively AWD by using the electric drive on the rear wheels for one thing.

It was also interesting that they found the 3008 mpgs dropped off rapidly in either hot or cold conditions. UDDS cold start was 30mpg at -7C, 31mpg at 35C and hot start 46mpg at -7C, 40mpg at 35C all using the manufacturer supplied loading conditions that result in higher mpgs.

It may be that the 3008 is better optimized for the European driving cycle tests, and the Prius is optimized for the US driving cycle tests, but I would call this one at best inconclusive.

3008 Test Report: http://www4.eere.energy.gov/vehiclesandfuels/resources/merit-review/sites/default/files/vss031_rask_2013_o.pdf

Prius Test Report: http://www.ipd.anl.gov/anlpubs/2010/06/67317.pdf

 

I'm reading the Urban Cold as a cold start. These test cycles aren't long, and that would easily explain the difference between it and a warmed up Extra-Urban result. The newer v/+ may incorporate some tweaks that allow faster ICE warm up. The 7 seat + also uses a lithium battery.

Also keep in mind that the US tests under report diesel mpg when compared to user reported numbers. In a study leading up to the the test changes in 2008, the EPA reported the average under reporting was 18% compared to the new, adjusted window sticker numbers. Hybrids' reported numbers were close, but still slightly under, the sticker numbers.

An efficient engine without technology to speed up warm up time could explain the poorer cold numbers. Perhaps cooling for the battery is limited in regards to the hot numbers.

A strong possibility. I wonder if a difference would be present between an American, Asian, and European market Prius. There are operating differences in the PPI.

 

Why didn't you get 75+ mpg in the Prius at that speed? Much less practice with HSD than with IMA?

With your driving situation -- 99% slow highway that is ideal for IMA, essentially no city where it falls well short of HSD, no need for the much larger cargo capacity that comes with the 13% heavier / 6% larger aerodynamic cross section of the Prius, and willingness to use a (no longer available) stick shift instead of automatic -- your needs fit extremely well to the Civic's strengths. If it had been available as a hatchbatch, I probably would jumped to it from my Accord Hatchback several years earlier.

But for most people who must drive in city traffic, your Otto HCH is a less ideal fit, no match for an Atkinson Prius. While the EPA Highway ratings are close, the more commonly useful Combined ratings show a much larger gap.

Back to my earlier post -- How are you estimating the mpg of your theoretical diesel-hybrid Prius?

 

Well, here's one example. This particular study comparing otto/atkinson/diesel cycles in the context of the original toyota prius ths and honda civic ima found that in this application the improvement in combined driving cycle fuel economy was 13% switching from Otto to Diesel, and 16% switching from Otto to Atkinson.

http://www.researchgate.net/profile/Theo_Hofman/publication/228965631_A_fundamental_case_study_on_the_Prius_and_IMA_drivetrain_concepts/file/72e7e5215bd1e018be.pdf

Rob

 

For what it's worth, Argonne National Laboratory's GREET model assumes a 40% increase in fuel mileage for gasoline-hybrid and 60% increase (gasoline equivalent) for diesel-hybrid over the baseline gasser. That's over 14% increase for the DHEV over the GHEV on an energy-equivalent basis, which would result in about 31% increase in fuel mileage taking the higher energy content of diesel fuel into account (GREET1_2013 assumes E10 gasoline).

Not sure if the ICE in the GHEV is assumed to be Atkinson cycle.