GM Chevrolet Introduces 2-Mode Hybrid Silverado; Launches Fuel Solutions
15 November 2007
|The Silverado 2-Mode hybrid pickup.|
At the Los Angeles Auto Show, Chevrolet rolled out the Chevrolet Fuel Solutions initiative designed to aggressively promote the fuel-saving technologies available in the brand’s current and future lineups. An accompanying parade of vehicles included a gasoline-powered subcompact (Aveo); a hydrogen fuel cell crossover (Equinox fuel cell electric vehicle); extended-range electric vehicle (Volt); and three hybrids.
The event included the world premiere of the Chevrolet Silverado Hybrid pickup truck, which will go on sale in North America later next year as a 2009 model. Chevrolet also revealed the all-new Malibu Hybrid sedan, arriving in North American dealerships this month.
Chevrolet also announced a historic partnership with the Walt Disney Company in which 10 Chevrolet Equinox Fuel Cell vehicles will be deployed as shuttles at Disney properties in California.
The 2-mode Silverado. The hybrid Silverado combines the 2-mode Electrically variable Transmission (EVT) with the 6.0L Gen IV V8 engine with Active Fuel Management (GM’s cylinder deactivation) and an Energy Storage System.
The all-new EVT is an assemblage of two 60 kW electric motors, three planetary gearsets and four traditional hydraulic wet clutches. This arrangement allows continuously variable operation, as well as providing four fixed gear ratios (with operation comparable to that of a standard electronically controlled automatic transmission).
The design was selected because of the operational characteristics of electric motors, which are very efficient when turning at low speeds, but much less efficient as motor rpm increases. Current hybrid passenger vehicles run their electric motors almost continuously throughout the entire drive cycle, which can be very inefficient under high loads and at highway speeds. The opposite is true with GM’s EVT, which can activate any of its four hydraulic clutches to allow power to be transferred via the fixed-gear ratios whenever high load conditions are experienced.
A Hybrid Optimizing System (HOS) constantly receives torque-based data from the powertrain and other vehicle systems, and then determines the most efficient means of propelling the vehicle—either via electric power, gasoline engine power or a combination of the two. The EVT is like having two transmissions in one – continuously variable drive for light-load conditions and fixed-ratio drive for high-load situations.
All functions of the EVT are controlled by the HOS, which constantly searches for the optimal transmission operation (using either variable or fixed ratios) to meet current operating conditions. The HOS also bases its decisions on allowing the Vortec 6.0L V-8 to take full advantage of its Active Fuel Management system and, because of an equivalent 30-horsepower (22 kW) boost of electric power, remain in V-4 mode as long as possible for maximum fuel economy. This is the basis of the Silverado Hybrid’s 25% improvement in combined city/highway fuel economy.
Unlike other hybrid systems, this new GM system occasionally shuts down the electric motors, allowing the EVT to function as a conventional automatic transmission. Typically, this fixed-ratio operation occurs at highway speeds or when hauling heavy loads, and can actually be more efficient than operating in electric-gasoline hybrid mode under the same conditions. This is because under high-load situations, when the fixed gears are in use, the electric motors can be used to generate electricity—or, if needed, they can be called on to supply additional torque for improved performance.
Energy Storage System. Providing power to the EVT’s two electric motors is a 300-volt nickel-metal hydride Energy Storage System (ESS). This battery pack is located under the second-row seat, where it takes up virtually no additional space and does not interfere with second- or third-row ingress/egress.
The primary function of the ESS is to provide power (300 volts) to the EVT via the Traction Power Inverter Module (TPIM) and to store captured energy produced during regenerative braking. The ESS can also be charged, when necessary, by the gasoline engine via one of the two electric motors when operated in generator mode.
In addition to supplying power to the EVT, the ESS also provides power to the air conditioning compressor and the Accessory Power Module (APM), which converts the high-voltage supply to 42 volts for the electric power steering system, and 12 volts for the vehicle battery and other 12-volt electrical accessories.
Battery pack durability and reliability is maintained via optimized charge and discharge cycles, as well as a dedicated cooling system that draws air from the passenger compartment. As part of the vehicle’s emission control system, the ESS is warranted for eight years/100,000 miles.
The ESS also has numerous safety features that prevent over-charging, over-heating, unintended access to high-voltage components and infiltration from liquid spills.
Regenerative braking. During braking, the Silverado Hybrid uses one or both of the EVT’s traction motors as a generator, converting the braking energy to electrical energy for storage in the ESS for future use to propel the vehicle.
The regenerative brakes are used along with the standard hydraulic brakes to slow the vehicle and/or bring it to a stop. Depending on the amount of braking force required, the hydraulic brakes may not even be used, such as during mild deceleration when slowing to allow space for merging traffic near a highway on-ramp.
When additional braking is called for, based on a change in the position of and/or the force applied to the brake pedal emulator, the hydraulic braking system will be called on to assist the generator(s) in slowing or stopping the vehicle. The anti-lock braking system (ABS)/Electronic Stability Control (ESC) modulator used on the Silverado Hybrid has been adapted to allow this interaction between the hydraulic brakes and the regenerative braking system.
The use of cooperative control between the regenerative braking system and the hydraulic brakes results in excellent braking control and maximum energy recovery. The system also provides feedback in the form of brake pedal resistance, which gives the driver the same feel as would be experienced with a normal hydraulic braking system.
Regenerative braking has the additional benefit of extending the life of the friction materials used in the hydraulic braking system, as well as improving braking performance in the form of shorter stopping distances.
6.0L V-8 engine. The Silverado Hybrid’s 6.0L V-8 engine is unique. It features Active Fuel Management and late-intake valve closing (modified Atkinson-cycle combustion process) for reduced pumping losses and better overall fuel economy.
The engine uses flat-top pistons, cylinder heads borrowed from GM’s 5.3L high-output V-8 and a 10.8:1 compression ratio, producing 332 horsepower (248 kW) at 5,100 rpm and 367 lb-ft of torque (497 Nm) at 4,100 rpm. It runs on regular unleaded fuel.
A key contributor to the Silverado Hybrid’s fuel economy is the gasoline engine’s Auto Stop mode. Once the vehicle reaches 0 mph, depending on the current state of the battery charge, the gasoline engine can automatically shut down. By leaving the engine off and allowing the vehicle to move only under electric power, such as during heavy stop-and-go traffic, fuel consumption is greatly reduced.
However, when extra power is required, such as for wide-open-throttle acceleration from a standing stop, the Vortec 6.0L V-8 is seamlessly restarted so it can deliver the necessary power and torque. In this case, the engine is restarted effortlessly from the Auto Stop mode using the EVT’s powerful internal electric motors; there is no traditional starter motor.
Fuel economy figures for the Silverado Hybrid are not finalized, but GM projects 40% greater city fuel economy and a 25% improvement in overall fuel economy over the full gasoline version. The 2008 Silverado with 6.0-liter engine is EPA rated at 13 mpg city, 18 mpg highway, 15 mpg combined.
Complexity always scares me, so I hope GM did its homework on this. I guess to that end, it is a little consoling to see the finicky engineers at Mercedes and BMW, (and that's meant as a compliment) signed on to this concept. Next hurdle is to make it affordable for the majority of the pick-up buying populace.
Posted by: Schmeltz | 15 November 2007 at 08:46 AM
Nice to see some analysis regarding the value of each of the components installed and how they contribute to fuel savings as well as operation of the vehicle.
For those who need hauling capabilities this is a winner.
Posted by: Ed | 15 November 2007 at 09:11 AM
A 25% improvement for a vehicle like this is very significant. Guess GM is finally getting serious about efficiency. Wonder how much over the regular version it is.
Posted by: Cervus | 15 November 2007 at 09:12 AM
If it is using the same 6.0L V8 from Yukon and Tahoe hybrid, the emission of this hybrid will be higher than the "gas-only" version.
Folks, this is the first time in hybrid history that the hybrid version has higher emission than the "gas-only" model.
Posted by: usbseawolf2000 | 15 November 2007 at 09:25 AM
We can't buy this truck with anything smaller than an 8cyl 6liter? Thanks but no thanks.
Posted by: Mick | 15 November 2007 at 09:42 AM
Sorry Cervus I don't see that. The E-85 might be slightly cleaner - but NOBODY actually uses E-85 and lifecycle wise it is not cleaner. I plan to serious look at the new silverado, espically since my escape hybrid is getting older and i like the features of the silverado (electric A/C finally). I just doubt GM will actually MAKE any of them. GM is great on hype, but they seem very poor at getting the product on the street. The Tahoe and Yukon are still not out there yet.
Posted by: Chris | 15 November 2007 at 11:06 AM
Or you could just buy a Civic. Yes a regular one, no hybrid.
Posted by: Robert Schwartz | 15 November 2007 at 11:10 AM
hm, what a load of pr. check out this gem:
«Unlike other hybrid systems, this new GM system occasionally shuts down the electric motors, allowing the EVT to function as a conventional automatic transmission»
where did they find such systems? none of toyota's hybrids run the electric motor(s) continuously.
Posted by: lensovet | 15 November 2007 at 11:13 AM
UNBELIEVABLE!! Who the hell is going to buy this?
No one is going to trade in a Prius for this, or even a Ford Escape. Joe Nascar ain't buying it. My guess is GM will sell a few hundred of these to government agencies that have been mandated to be Greenwashed.
Posted by: DS | 15 November 2007 at 11:22 AM
Seriously. I don't understand the hatred I see here. I thought that this is something folks here wanted to see. We have a major automaker making significant efficiency improvements for its large trucks and SUVs.
I guess it's the vehicles themselves that some people hate, no matter how efficient they could get.
Posted by: Cervus | 15 November 2007 at 11:37 AM
Seriously. I don't understand the hatred I see here. I thought that this is something folks here wanted to see. I guess it's the vehicles themselves that some people hate, no matter how efficient they could get.
I think you need to relook at your own responses to certain things before you start passing judgment on others.
Posted by: | 15 November 2007 at 11:40 AM
The 2008 Silverado with 6.0-liter engine is EPA rated at 13 mpg city, 18 mpg highway, 15 mpg combined.
OUCH. That's gotta be painful at the pump.
Posted by: BMW_4_ever | 15 November 2007 at 12:10 PM
Like it or not, your groceries don't get delivered to the grocery store via prius. This technology should eventually wind up in all sorts of GM commercial vehicles and will save tons and tons of fuel and emissions. GM sells lots and lots of commercial vehicles and I think they are not part of CAFE standards. Think longer term before you compare this truck to a prius and bash GM!
Posted by: | 15 November 2007 at 12:55 PM
At 15mpg combined, 15k miles per year, that comes out to 1,000 gallons of gasoline.
Final MPG for this vehicle hasn't been finalized, but looking at the Chevy Tahoe Hybrid, EPA combined is 21mpg. 714 gallons of gasoline, for a savings of 286 gallons.
By comparison, my Corolla gets 35mpg. It would use 439 gallons over the same year. In order to save the same amount of fuel, mileage would have to more than double.
With consumer preferences the way they are, I think it's better to make efficiency gains at the bottom. A 25% improvement when you're only getting 15mpg combined will have a huge impact on overall fuel consumption.
Posted by: Cervus | 15 November 2007 at 12:56 PM
Like it or not, your groceries don't get delivered to the grocery store via prius.
Winner: Dumb Comment of the Day
Posted by: DCOTD Jury | 15 November 2007 at 01:37 PM
A lot of the discussion here points to something I've been saying for a while--we need to distinguish between people who buy pickup trucks simply because they want one and those who buy one because they truly need one.
We all know people who work in an office and have no special need for a truck yet own one anyway. And we all likely know people (like my brother-in-law) who can't run a business without such vehicles.
My preference is to heavily tax the discretionary use of such vehicles by the former group (high yearly registration fees, perhaps), to push those drivers to more reasonable vehicles, and let the normal cost-cutting in response to rising gasoline prices provide most or all of the impetus for commercial users to buy the most efficient truck possible.
Posted by: Lou Grinzo | 15 November 2007 at 01:47 PM
FINALLY a hybrid that could reasonably be used as a service vehicle!!!
Now, GM, put this in the Express van @ $30k and I'll buy 4!!!
Reguarding : " Like it or not, your groceries don't get delivered to the grocery store via prius." ... I would rephrase this... the refrigeration that keeps your food safe to eat is not repaired and maintained by equipment carried in a Prius, nor is your home A/C, plumbing, or electrical, or any other service industry, fixed by somone carrying things in a Prius, it simply won't hold what's needed.
When a company spends $10,000 a year in fuel per vehicle at current prices, these vehicles are going to become very attractive.
The real winner of the dumb comment of the day: "No one is going to trade in a Prius for this..."
Posted by: Ash | 15 November 2007 at 01:47 PM
Posted by: DS | 15 November 2007 at 01:54 PM
"none of Toyotas hybrids run the electic motor continuously"
This is not correct, the Prius uses one of it's motors as an input into the plantary gear set of the transmission to change the gear ratio.
Posted by: Tim Russell | 15 November 2007 at 01:57 PM
The 6.0L used here is essentially the same engine as used in gas-only variants, but modified to implement an Atkinson cycle. That is why they didn't use the 4.8 or 5.3L engines, which were also considered.
Plus, the 6.0L carries a higher margin so it's easier to play hide the salami with the high cost of the two-mode hybrid system.
Posted by: Rafael Seidl | 15 November 2007 at 02:07 PM
Look pretty damn good for a 6.0 litre ICE. The 25% mileage improvement does show a concerted effort to address fuel efficiency in large vehicles. Thing about hatred is - it's hard to stop once it gets started.
Posted by: gr | 15 November 2007 at 02:27 PM
"Like it or not, your groceries don't get delivered to the grocery store via prius."
They don't get delivered in pick up trucks either. Some groceries DO get delivered in these though.
Posted by: domenick | 15 November 2007 at 04:12 PM
Posted by: DCOTD Jury | Nov 15, 2007 1:37:37 PM
My preference is to heavily tax the discretionary use of such vehicles by the former group (high yearly registration fees, perhaps), to push those drivers to more reasonable vehicles, and let the normal cost-cutting in response to rising gasoline prices provide most or all of the impetus for commercial users to buy the most efficient truck possible. .[/Quote]
How would you distinguish legitimate truck users from those who really don’t need a truck? I’m all ears.
I hope you plan to introduce incentives to make Al Gore fly commercial and make Snowmobiles, Jet-Skis, Power Boats, Houses over 2500 square feet, Second homes of any sort, etc., etc. so expensive only Bill Gates and Warren Buffet can afford them. I don’t want to live in your world where I have to drive a vehicle you deem to be “reasonable” for me. I’ll decide what vehicles, houses, and toys are reasonable for me!!
Posted by: Yukaburbahoe | 15 November 2007 at 06:25 PM
Enough of the criticism of GM because at least GM has made a large hybrid pickup truck for sale in America. So how come nobody mentioned the lack of any Dorf, Cerberus, Nissan and Toyota's hybrid pickup trucks?
Posted by: gary | 15 November 2007 at 06:40 PM
Your responce was perfect. No need to re-evaluate.
As you state - no level of improvement of this type of vehicle is going to make some of these people happy. For some, any article about GM is sure to prompt hate mail from some of the regulars here. Sad.
Posted by: Steve | 15 November 2007 at 06:51 PM