Not all hybrids are born equal!

[Brian Ellis]

The fuel consumption of hybrid cars are often just as bad, or even worse, than many conventional cars. The following is a list of hybrids and their approximate 33/33/33 highway/rural/city aggregate consumption (derived from a number of sources) in litres/100 km : EPA air pollution score (based on emissions quality, not on volume)

Toyota Prius 5.4 : 8
Honda Civic Hybrid 5.6 : 9

Nissan Altima Hybrid 7.1 : NA
Toyota Camry Hybrid 7.1 : 8
Ford Escape Hybrid FWD 8.1 : 8
Ford Escape Hybrid 4WD 8.9 : 8
Mercury Mariner 4WD 8.9 : 8
Honda Accord Hybrid 8.9 : 9 (discontinued)
Saturn Aura Hybrid 8.9 : NA

Lexus RX 400h 2WD/4WD 9.2 : 8
Toyota Highlander Hybrid 2WD/4WD 9.3 : 8
Saturn Vue Hybrid 9.4 : 6
Lexus GS 450h 10.5 : 8

Chevrolet Silverado Classic 15 Hybrid 2WD 14.2 : 3
GMC Sierra Classic 15 Hybrid 2WD 14.2 : 3
Chevrolet Silverado Classic 15 Hybrid 4WD 15.0 : 3
GMC Sierra Classic 15 Hybrid 4WD 15.0 : 3


As expected, the Prius and Civic are way ahead and the big pick-ups are worst, from the point of view of consumption, each in a class of their own. I wonder why the two Honda's in the list are less polluting than all the Toyotas and Lexus + a few others and why the pick-ups are very much worse, according to the US EPA?

The colour coding is arbitrarily chosen by me: green = <6 l/100 km, blue = <9 l/100 km, black = <11 l/100 km and red = >14 l/100 km (none fitted in orange <14 l/100 km).

[Dr Mordrid]

All parallel hybrids?

If so it shows the fallacy of having two distinct drive lines with the electric 'helping' the IC instead of vice versa as in serial hybrids.

Interesting news item: Chrysler LLC (now private) just started ENVI, an electric car division, and stole Jim Press from Toyota to oversee sales, marketing and product strategy. Press was President of Toyota Motor North America and the first non-Japanese member of Toyota’s board of directors. He is widely regarded as being largely responsible for Toyota's gains in the US market since taking over.

Sounds like the ENVI schedule will be very aggressive;

Chrysler says the ENVI initiative will research and build new products from the ground up that will be sold under the Chrysler, Dodge and Jeep nameplates — rather than retrofit existing models as hybrids. A Chrysler spokesman said speed to market will be a priority.

Chrysler chief Thomas LaSorda called ENVI "a start-up with an entrepreneurial environment" rather than a pure research organization, and said the unit will be expected to "develop appropriate solutions quickly."

One way to do that would be to hook up with an outfit like TM4 (part of the Hydro-Quebec group) who makes the electric car motors (including wheel motors), small IC generators & control systems necessary for series hybrids.

TM4 is already working with several other manufacturers.

[LvR]

EPA air pollution score (based on emissions quality, not on volume)

IMO there must surely be a "volume" (of polluted air produced) factor involved there.

I cannot see how/why the design of modern big capacity fuel burning engines would necessarily be more than double as bad (green/efficient) as smaller capacity designs.

[Brian Ellis]

OK, I have some thoughts about GM's "hybrids". Firstly, the Silverado and Sierra are not really hybrids at all, as there is no energy given to the wheels except from the ICE: no electrical assistance. The whole engine/exhaust/transmission etc. is a prehistoric design. The only change from the non-hybrid models is the fact that the engine stops when the car stops and starts again as soon as the foot is lifted off the brake pedal. The only fuel saving is therefore in urban traffic and is minimal. The engine design is probably basically >15 years old and is built for ruggedness, not for the environment. This is my explanation for the low figures cited, but I may be wrong, as I can't second-guess the EPA's reasoning.

The other below-par model is the GM Saturn Vue. I haven't been able to suss out the origins of the engine; I suspect it comes from an oldish European car, possibly the Opel Omega, because GM's own prediction is very low production figures for this model and a new engine design would seem unlikely. The 2.4 l version was made from 1997 to 2003 and the later models were considered very good for performance and economy. It also met Europe's tight pollution standards. Certainly, it has nothing in common with the engine of the non-hybrid Vue.

[Dr Mordrid]

The 2-mode hybrids (AKA: Advanced Hybrid System 2 or AHS2) used in the larger GM vehicles and the Vue hybrid have 2 electric motors in the transmission to provide boosting and regenerative braking. This was developed by GM, Daimler-Chrysler and BMW as a means to get some hybrid functionality into existing models ASAP. 2-mode tranny cutaway image at the bottom of this posg. Note the 2 large motor windings surrounding the rest of the works.

The 2-modes operate along these lines;

In summary, the four fixed gears overlay two ECVT modes for a total of six operating functions:

* Input-split ECVT mode, or continuously variable Mode 1, operates from vehicle launch through the second fixed gear ratio.

* Compound-split ECVT mode, or continuously variable Mode 2, operates after the second fixed gear ratio.

* First fixed-gear ratio with both electric motors available to boost the internal combustion engine or capture and store energy from regenerative braking, deceleration and coasting.

* Second fixed-gear ratio with one electric motor available for boost/braking,

* Third fixed-gear ratio with two electric motors available for boost/braking.

* Fourth fixed-gear ratio with one electric motor available for boost/braking.

The Volt system is far, far different being a vehicle designed to run 100% of the time in electric mode with assistance being provided by the ICE in the form of charging the batteries. Since this is a minor job it can be done by a tiny (1.3l 3 cyl) turbocharged gas or diesel motor using a very limited RPM range of operation.

The 2007 Vue Greeen Line plug-in hybrid's engine is the GM Family II 170 hp (127 kW) 2.4 L Ecotec DOHC-phaser engine, which is based on the 4 banger used in the 70's Opel Ascona B and Opel Kadett D. Since then its evolved gaining DOHC, EFI and other improvements. Until the Vue the main users haver been Holden and GM do Brasil.

A Gen-II Vue hybrid is slated for 2008 will be based on the Opel Antara.