Nick P.

GM has made efficient cars for years, but you're too stubborn to want to believe it. And trust me GM's vehicles are a lot more attractive than Honda's and Toyota's are. Malibu and Aura versus Camry and Accord? SKY and Solstice versus ??? Full size trucks from GM versus the ugly Toyotas? It's no contest.

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yes, GM has made small efficient cars -- but the styling suggested that it's just a stopgap car that you can drive until you can afford one of GM's "real" vehicles.

Contrast the Cobalt with, say, the Mini Cooper or the Prius and you'll see what I'm getting at. The Mini Cooper, VW Jetta , and the Prius have enough features and character to compete directly with larger vehicles for a certain buyer. Both the Jetta and Mini cooper will attract the kind of buyer who wants a zippy little car that's still practical enough to be a daily driver. The Prius attracts technology buyers and environmentalists with the hybrid drivetrain and its spaceship looks. Compared to that, what does the Cobalt offer?

Another data point would be the Ford Focus. Look at the pre-2008 ford Focus... I drove a rental 2001 Ford Focus for two weeks in 2001 (after my 1989 Ford Tempo had been rear-ended), and I wasn't convinced that it was any better than my old beater with either looks, performance, or features. Compare that to the 2008-2009 Ford Focus -- it's probably the same car, but some subtle changes to the styling make them look like a car that you don't have to be poor to drive, and I've been seeing an awful lot of them on the road. The Focus is likely to be even more competitive after the Euro Focus will be sold in the US in a year or two.

So, yes, GM has made efficient cars over the last 5 years or so -- but they didn't target them at buyers who have a choice about what car to buy. So, those of us who want a small car just because we like them are very likely to end up driving a foreign car. I hope this will change with the Volt and the Cruze, but time will tell.

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"SKY and Solstice versus ??? "

EXACTLY. How much development did they pour into that car only to find what everyone else already knew, there is no market for it.

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UH2L:

> comparable effiiciency

The efficiency will not be comparable because HCCI shaves of 18% while hybridization manages 27-30%.


> to heavy, complex hybrid powertrains.

I think some education about hybrid drivetrains may help. You'll realize that these are the SIMPLEST drivetrains in the market now. Hybrid Synergy Drive requires:
- neither an automated (dual) clutch nor a lockable torque converter
- neither a complex gearbox with multiple mechanically/hydraulically actuated gearmesh and multiplate wet clutches as in case of dual clutch gearboxes or automatics

Hybrid Synergy Drive also employs possibly the simplest engine in the market yet one of the most efficient one as far as brake specific fuel consumption is concerned. These Atkinson cycle powerplants require no turbocharging, no direct injection, no variable valve timing, no additional exhaust treatment components.

What HSD adds are components with no moving parts (a battery, an inverter) and electric motors that are rather simple things, aren't they?


> Malibu and Aura versus Camry and Accord? SKY
> and Solstice versus ??? Full size trucks from GM
> versus the ugly Toyotas? It's no contest.

It's cool to share opinions but I rather prefer facts.


> Speaking of GM and fuel efficiency, I drove my mom's
> 2004 Saab 9-3 Linear 2.0 t 5-spd automatic, and with
> less than 10 mph diagonal winds and a 300 ft elevation
> drop over 28 trip

It's even cooler you drove something somewhere or maybe you didn't but the real life observed fuel economy of this car is 24-26 mpg.

People get it. Edmunds got it. EPA rating is 21 mpg.

http://www.edmunds.com/insideline/do/Drives/FullTests/articleId=79822/pageId=36085
http://fueleconomy.gov/mpg/MPG.do?action=mpgData&vehicleID=19656&browser=true&details=on

The car does 0-60 in 8.1 sec. Brilliant, the Camry Hybrid is 0.5 slower and people get 36.5 mpg out of it. Do you have anything to add as far as fuel economy is concerned?

http://fueleconomy.gov/mpg/MPG.do?action=browseList2&make=Toyota&model=Camry%20Hybrid

Oh, I nearly forgot. Nissan Altima Hybrid with the HSD tuned for performance does 0-60 in 7.5 sec and returns 34 mpg.

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@downtoearth:

"> comparable effiiciency

The efficiency will not be comparable because HCCI shaves of 18% while hybridization manages 27-30%."

Dude, keep drinking that Kool-Aid. Where'd you get those numbers? 27-30% saved? Seriously...?

Combined Fuel Economy (according to EPA)
Lexus GS350 - 10.7L/100km
Lexus GS450h - 10.2L/100km

That's less than 5%.

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Kevin:

> Dude, keep drinking that Kool-Aid. Where'd you get those numbers?

> Combined Fuel Economy (according to EPA)
> Lexus GS350 - 10.7L/100km
> Lexus GS450h - 10.2L/100km

Why are you comparing a performance oriented hybrid vs its ordinary rival without considering the performance?

From Lexus.com:
GS350 0-60 = 5.7 sec
GS450h 0-60 = 5.2 sec

Doesn't sound like much but here's the better thing:

" but for all that it sprinted to 60 mph in 5.5 seconds and covered the quarter-mile in 14.1 seconds at 103 mph. This was a shade quicker than the M45, as well as the GS430, and more important, the 450h posted the best 30-to-50 and 50-to-70 times in the group, performance that made it impressive in back-road passing maneuvers."

Source: http://www.caranddriver.com/reviews/comparison_test/sedans/2007_bmw_550i_vs_infiniti_m45_lexus_gs450h_m_b_e550_comparison_test+page-2.html

So the GS450h can top some V8 (!) sedans in terms of 0-60 acceleration and tops all the compared V8 ones (Infiniti M45, BMW 550i, Mercedes E550) in terms of passing/in gear acceleration.

Funny you failed to mention that.


> 27-30% saved? Seriously...?

Yes. Let's prove it.

Nissan Altima Hybrid:
0-60 in 7.5 sec
EPA Comb = 34mpg = 6.91 l/100km
EPA used shared (28+8 samples)= 34mpg = 6.91 l/100km

VW Passat 2.0 TFSI:
0-60 in 7.7 sec
EPA Comb = 23 mpg = 10.22 l/100km (48% more than Altima)
EPA user shared (4 samples) = 25.3 mpg = 9.29 l/100km (34.4% more than Altima)

I took two cars that offer the same performance, the same size, the same body type and shape, the same drivetrain type (FWD automatic) and took even real life estimates to ensure a realistic comparison.

I also picked the most efficient ordinary gasoline setup - a downscaled engine with a turbocharger and a direct injection.

I can continue on and on with the Camry vs Camry Hybrid, the Prius vs Corolla but in no other case so many aspects will be matched. For instance the Camry Hybrid is significantly faster than a 4-banger one but slower than a V6-one. Prius on the other hand employs additional means of saving fuel (tires, shape) and is also a big larger than a Corolla.

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This 8-speed would have to have an increased spread to make it up to that speed at the lower HCCI rpms, and then the car would have to be making sufficient horsepower to get up to that speed. Since HCCI is RPM limited, not speed limited, and knowing how far my own car tops out at in its highest gear with a bigger torque-ier engine around 2500-2600 rpm (just above 90 mph with the torque converter locked in 4th), it probably just does not have the horsepower to hit 100 mph. This is assuming similar Cd and max torque around 180 lbs-ft at 3000 rpm (just over 100 hp).

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Then again, I could be wrong if HCCI can run well above 3000 rpm (think up to 4k) and the gearing was just right. But that might compromise real-world efficiency.

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If it's heavily constrained by RPMs this is one of those cases where a CVT would make a really big impact in keeping in the right rev range.

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mike:

> Why one versus the other? How about one of these in a hybrid?
> Best of both worlds? 15% more MPGs than an avg hybrid... Not bad.

Mike, the thing is hybrids already employ an efficiency boosting technology in their gasoline engines which is much cheaper than HCCI and works only a tad worsel. It's called an Atkinson cycle.

Results are very significant. The Toyota Prius engine peak thermal efficiency is 37% as observed by the Argonne National Lab: http://www.transportation.anl.gov/pdfs/HV/2.pdf

Now if we assume gasoline energy density being 46 MJ/kg = 12,78 kWh/kg this will equal to 211 grams of fuel to produce 1kWh of energy, as break specific fuel consumption is measured.

How good it is?

Well, very good. The best result for a comparable Volkswagen DIESEL engine is 201g/kWh: http://www.vw-industrial-engines.com/industrial-engines/models/diesel-engines/tdi-20-463-mc/index.html?L=1

Other engines get 211, 214 g/kWh.

And these are pump-unit injector diesels which are more efficient as common rail ones when comparable injection pressure is at stake.

Now a good gasoline engine returns maybe 240g/kWh peak. Slash it by 15% and you'll get some 204g/kWh. A tiny improvement with a lot of cash invested since Atkinson engines are ruthlessly simple and durable while HCCI ones will likely be opposite of this.

Naturally, this reasoning is superficial, one need to consider the shape of entire efficiency map and efficiency drops in various rev/torque areas but the first sings suggest that planting a HCCI engine in a hybrid will bring miniscule benefits.

Question is - can you marry the HCCI principle with the Atkinson cycle. Maybe this would help.

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Excellent posts downtoearth. A lot of people do not realize Prius gas engine is as fuel efficient as Diesel, even with the ~15% less energy in the fuel. They are comparable on the highway but there is no contest to HSD in the city.

There were further BSFC improvements made in the 2010 Prius with 1.8 liter ICE. See: http://priuschat.com/forums/members/ken1784-albums-2010-prius-picture1281-bsfc.jpg

It looks like the 1.8 liter latest generation of Atkinson cycle engine is approaching 40% efficiency.

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HCCI is actually very well adapted to range extender duty, where the rev range doesn't matter. I wouldn't be too surprised if an HCCI engine is offered on the Chevy Volt someday (provided GM lasts long enough).

A CVT is another way to reduce the range of required engine speeds, but the ratio range would be limited. A transmission with 6 or more ratios is probably close enough already. I just hope that GM can extend HCCI operation up to 75 mph, because no one goes 60 on the highway unless they want to impede the flow of traffic.

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Yes, downtoearth, it should be possible to combine Atkinson/Miller cycle with HCCI. The key feature of the Atkinson cycle is that the power stroke is longer than the compression stroke, that enables engines so equipped to extract more power from the hot burned gasses. HCCI improves thermodynamic efficiency. Combining the two will still give higher thermodynamic efficiency, plus extract more energy, resulting in higher efficiency than either of those techniques alone.

It can also be hybridized for even better fuel economy, all three economizing techniques are compatable.

Of course, there are major technical challenges in HCCI, as the compression ignition process is similar to the process that causes knocking and engine damage in high performance engines running on low octane fuel (BTW, that means that HCCI engines requires low octane fuel and won't run well on premium!)

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