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Silverado Hybrid…Emergency Power
From cruising speed, you lift off the gas pedal and either coast to a slower speed or apply the brakes to stop. Either way, when the vehicle slows to 13 mph, the engine automatically shuts off. You still have power steering. You still have power brakes. Then almost faster than you can react, as you lift off the brakes and go for the gas pedal, the engine quickly and silently starts. The operation is seamless. And you save every drop of gasoline normally used during idling.
As a rule, the gasoline engine in the Silverado Hybrid shuts off every time you come to a stop sign, every time you stop for a stop and go light, and every time you slow to turn a corner. The engine shuts off at every stop, regardless of reason. Any time the vehicle slows below 13 mph and the transmission is in Drive or Third, the engine shuts off.
Many Definitions for Hybrid
The term “hybrid” means a lot of things! Basically, it means a combination, i.e., a hybrid, of a traditional gasoline powered engine and some other drivetrain feature, in this case, literally any other drivetrain feature.
As a generalization, two kinds of hybrid electric vehicles exist. One is the parallel system, where both drivetrains work at the same time. This has come to be called a “full” hybrid. The other is the series configuration, where each system works separately, one or the other. This has come to be called the “mild” hybrid.
Loosely defined, the Ford Escape Hybrid is a “full” hybrid. That battery pack combines with a massive electric motor to actually move the vehicle up to 25 mph under normal driving conditions. That hybrid system also shuts off the engine at a stop and instantly restarts it as heavy acceleration is needed or as speeds increase above 25 mph. The Escape Hybrid can be powered by the gasoline engine only, the electric motor only, or both at the same time.
Loosely defined, the Silverado Hybrid is a “mild” hybrid. The hybrid battery pack does not provide any propulsion for the truck. The hybrid feature simply shuts the engine off at a stop and then rapidly restarts the engine. The other hybrid aspects of the Silverado Hybrid also include electro-hydraulic power steering, electro-hydraulic power brakes and an HVAC system that instantly shifts from compressor use to fan-driven recirculated air.
To avoid any confusion whatsoever, the Silverado Hybrid is NOT an electric vehicle. It never needs to be “plugged in.” The mild hybrid system does NOT power the truck forward at lower speeds like some full hybrids. The mild hybrid system does NOT provide extra power for passing like some full hybrid vehicles with small gasoline engines. The Silverado Hybrid has a 295 hp V-8 for launches and passing! The Silverado Hybrid can be driven without using the hybrid function but the hybrid equipment cannot drive the truck if the gasoline engine fails.
The Silverado Hybrid does not use an electric motor to drive the truck at all. The Escape Hybrid does use an electric motor for some propulsion. That is the main difference between mild and full hybrid technology, at least in today’s terms.
The “mild” hybrid option for the Silverado provides only slightly better fuel economy but costs significantly less than “full” hybrid options. The full hybrid option adds about $3,500 to the Ford SUV. In contrast, the mild hybrid option adds $1,500 to the GM pickup.
How It Works
Instead of using a conventional starter motor and alternator, the Silverado Hybrid uses a 14-kilowatt electric motor (starter generator). This provides extremely fast and totally quiet cranking power for automatic engine starts. This Flywheel Alternator Starter (FAS) system is integrated with the flywheel and torque converter inside the transmission bell housing. This is controlled by the Starter Generator Control Module (SGCM), which is located on the passenger’s side firewall under the hood. The SGCM is definitely self-contained: It has its own recirculating cooling system complete with a separate radiator, fan, cooling pump and surge tank.
The Silverado Hybrid has two separate battery systems. One is the traditional 12-volt battery, mounted under the hood. This powers many engine and body electrical demands, but not all. The other is a 42-volt battery pack, which is three 12-volt batteries mounted under the rear seat. This powers the starting system and is tied into the Auxiliary Power Outlets (APO).
If the 42-volt battery runs down, and thus the vehicle will not crank, it can be jumped with a standard 12-volt vehicle...but the initial jump charge before cranking may take 20 minutes.
The hydro-boost brakes on all Silverados (and Tahoes) get their boost from the power steering. An electric power steering pump on the Silverado Hybrid provides power steering and power brakes regardless of whether or not the engine is running.
Manual and Automatic Hybrid Override
The hybrid technology includes an automatic override feature. This causes the engine to either keep running while the vehicle is stopped, or causes the engine to start all by itself. For example, this will happen when the ambient temperature is above 95 degrees F and the HVAC is in Auto mode trying to keep the cabin cool, i.e., the A/C compressor needs to run. With the A/C in other modes, the vehicle will recirculate the cabin air, but the engine will not start.
The engine will remain running when the climate control is in the defrost mode since the load on the alternator is so high. The engine will also start or remain running when the battery pack charge is low, when the Tow/Haul button is engaged, when the transaxle is in 4LO, and any time any door is open while the vehicle is in Park.
The engine will also start or continue running when the engine is not yet warmed up, when it is necessary to maintain the 120-volt APO operation, when the shift lever is in Neutral, Reverse, Second or First, and finally when the brake pedal is released when the gear selector is in Drive or Third.
The hybrid function can be manually overridden, stopping all auto start/auto stop features. Simply press the Tow/Haul button located on the end of the column shift selector. The hybrid function defaults to the ON mode, so turning the ignition off and then on again enables the auto stop hybrid features. So does pressing the Tow/Haul button a second time.
You do NOT have to remember when the engine automatically starts and stops. Just let it do what it was engineered to do. In that regard, the drivetrain on the Silverado Hybrid is totally seamless.
It starts so quickly and runs so quietly, you need a tachometer to tell if the engine is running or not. Just get it, start the truck, drop it into gear, and go. The engine will auto shut off when it can and will auto start when it needs to. Ignore it. You do your job. It will do its job.
Auxiliary Power Outlets
The REAL advantage of the Silverado Hybrid is not improved gas mileage. Instead, it is ready access to portable electricity. The Silverado Hybrid is a combination pickup truck and mobile generator. THAT is what makes this truck important to law enforcement and all other emergency service providers.
Introduced in 2004, General Motors sent three dozen Silverado Hybrid trucks to Florida in response to Hurricanes Bonnie and Charley. The hybrid trucks provide 120-volt AC electricity, which can be a very precious commodity.
The Silverado Hybrid is equipped with four 120-volt/20-amp electrical auxiliary power outlets. Two are near the rear seat floor inside the cab and two are located on the side of the bed near the tailgate. These outlets provide electricity to run some tools and household appliances directly from the vehicle, while driving or when parked.
The 120-volt circuit may not be able to operate some motor-driven equipment and appliances with high initial (start-up) currents such as air compressors, table saws and fan motors. On the other hand, it will operate some of these, and virtually all non-motor driven devices, i.e., flood lights. If the hybrid equipment cannot start the device in five seconds, it will stop the attempt, and display a message in the Driver Information Center on the dash.
The Silverado Hybrid will provide 120 volts of power for 32 hours non-stop before the need to fill the gas tank. The APO has a low-fuel shutoff feature. The unattended vehicle will run for five minutes after a Fuel Level Low visual and audible alert. Then both the APO system and the engine automatically shut off before the tank is run empty.
Here is a real twist...the electricity comes from a “clean” generator. That engine’s exhaust goes through the full catalytic converter system and has less emissions than other gas and diesel-powered generators.
The Auxiliary Power Outlets (APO) can be used in two modes. The APO controls are on the dash. In Normal mode, the APO can be used while driving, i.e., when the vehicle is moving. This is a patrol officer’s dream come true...brew coffee while en route to a call. In Normal mode, the APO will work with the transmission in any gear. In Continuous mode, the vehicle can be parked, the ignition key removed, and the vehicle locked. The hybrid system will continue to provide 120 volts of household electricity.
The hybrid components carry an eight-year, 100,000-mile warranty.
We put 600 miles on the Silverado Hybrid during this evaluation. We carefully recorded the gas mileage under different driving conditions. Since this evaluation started to be all about gas mileage, as soon as we picked up the vehicle we set the proper tire pressures. The truck had 12,000 miles on the odometer, so it was well beyond breaking in. Finally, during the entire evaluation, we ran the 4x4 pickup in 2WD.
The 2WD Silverado Hybrid has EPA ratings of 18 mpg City and 21 mpg Highway. The 4x4 hybrid truck has EPA ratings of 17 mpg City and 19 mpg Highway. In a mix of 55 mph suburban and 35 mpg urban driving, we averaged 15.1 mpg. In a mix of 55 to 70 mph rural and interstate driving, we averaged 17.5 mpg. In rush hour, gridlock traffic we averaged 18.8 mpg.
The overall average during our 600 miles and week with the truck was 17.2 mpg.
Another credible automotive reviewer put 750 miles on the Silverado Hybrid in mixed driving from stop-and-go to interstates and achieved an average of 16.8 mpg. Taken together, we hit the EPA City rating right on the head. A comparable, non-hybrid Silverado 4x4 Extended Cab achieves between 14.9 and 15.1 mpg, actual.
Exactly how much gas does the Silverado Hybrid save? Under most cases, the hybrid function eliminates all idle time. According to both Chevrolet and Ford, a typical V-8 uses about ½ gallon of gasoline per idle hour. Depending on the municipal price for gasoline, the savings is about $1.00 per full hour of idling. It may take a lot of stop signs and stop lights, at a few seconds of idling each, to add up to a full hour of idling, i.e., to add up to $1.00 saved.
According to GM Fleet press releases, “Fuel economy is improved as much as 10% over standard gasoline engines.” The GM Web site is firmer, in stating that the hybrid system “delivers 10% to 12% improved fuel economy.” Depending on your driving routes, in fact, the Silverado Hybrid may also show no improvement whatsoever in gas mileage compared to a standard Silverado.
The resulting gas mileage from the hybrid pickup is extremely and entirely dependent on the driving route, i.e., not driving style so much as driving route. In urban driving with uneven traffic patterns but without a lot of complete stops, the Silverado Hybrid does not get to show off its hybrid technology. If you don’t come to frequent stops, or frequently slow to less than 13 mph, your mileage will be exactly the same as any 5.3L V-8 Silverado 4x4 Extended Cab.
Even if a 10% mileage improvement in realized, that is only 1.7 mpg. That is nice, but is unlikely to pay back the hybrid upcharge. And, you may not see any improvement in mileage. You could achieve equal mileage improvements by proper tire inflation, scheduled air filter replacements and driving just 5 mph slower.
GM Fleet, however, argues that a 10% increase in fuel economy from a high volume vehicle that gets 16 mpg is more beneficial (fuel-wise) than a 10% increase in a 30 mpg niche vehicle. Good point.
In rural and non-stop driving, the Silverado Hybrid uses none of the hybrid technology. In heavy urban traffic with frequent stop lights and especially, stop-and-go rush hour traffic, the Silverado Hybrid comes into its own. However, and here is the point, that is the only driving situation where the hybrid powertrain has a clear advantage. If the way you use the police pickup does not mirror gridlock traffic patterns in an urban patrol scenario, you may be disappointed with the improved gas mileage from the hybrid option.
The engine in the Silverado Hybrid appears to stop and start with a mind of its own. This takes a little getting used to. It will start and idle indefinitely in Park and Neutral...no gas savings there. If you put the transmission in gear, the truck will give you five seconds to go, otherwise the engine will shut off.
The engine shuts off when the vehicle slows below 13 mph, whether or not your foot is on the brake. With your foot on the brake, and the truck in Drive, as soon as you release brake pressure, the engine starts. If you reapply the brake, the engine shuts off after five seconds.
The Silverado Hybrid does not have a police-oriented suspension, of course. Even for a 4x4, the springs, shocks and sway bars are pretty soft. The pickup has lots of body roll and understeer when driven aggressively. The truck was not designed nor intended for high-speed, emergency or pursuit driving, of course, so don’t drive it that way!
In normal driving, the ride is very comfortable for a 4x4. Of course, the cab has gobs of headroom, legroom, shoulder room and hip room. The Extended Cab feature has plenty of space for police gear even though limited access to the battery pack under the seat is needed.
The Silverado Hybrid has two little driving quirks...beside the engine turning on and off whenever it wants to. First, the engine shuts off in Drive at a stoplight, of course, and it starts as the brake pedal is released. However, on an incline, the truck will roll downhill in the second or two between brake-off, engine-on and torque converter-engaged. This was not a major issue during our evaluation, but then we didn’t drive the truck in San Francisco.
Second, as the truck slows down and the engine speed gets around 1000 rpm, the truck does “something” that the driver can feel. That something is regenerative braking, which charges the battery pack. The regenerative braking feels a little like the vehicle has downshifted and is being slowed by engine braking. The hybrid system is taking energy from the moving vehicle, turning that into electric energy and storing that in the 42-volt battery system. It is an unusual sensation, but you get used to it quickly.
No Compromise Pickup
The Silverado Hybrid does not compromise acceleration, towing capability or hauling utility. It drives like the 5.3L V-8 pickup that it is and hauls whatever will fit in the standard bed, with room for three in the rear seat. You don’t give up any of the usefulness of a pickup to get the hybrid feature.
The hybrid drivetrain is available on 2WD and 4x4, Chevrolet and GMC, Extended Cab Short Box pickups. The battery pack is located under the rear seat, so an Extended Cab is required. All these are powered by the 295 hp, 5.3L V-8 and bolted to a 4L60E 4-speed auto overdrive trans. Three different axle ratios are available. Our test truck was the Chevy 4x4 with standard 3.42 rear gears. The Silverado Hybrid has emission certification levels of Federal Tier 2, Bin 8 (CFF LEV) and California SULEV.
The hybrid option was available to fleet operations in mid-2004, and in limited quantities to retail customers in CA, WA, OR, AK, NV and FL for the 2005 model year. This hybrid option is now widely available as a 2006 model. A full hybrid version of the Tahoe is planned for 2007. That promises to yield a 25% improvement in fuel economy.
The strongest feature of the Silverado Hybrid is the ability to act as a mobile electrical generator in a location where no outlets are available, or in the event of a power outage for any reason. And this full-size, V-8 powered, 4x4 truck will get you to those locations when needed. Each police fleet should have one of these...as should each post, barracks, troop or precinct. Forget the possibility of a small gasoline savings. Go for the mobile electrical power.
Published in Police Fleet Manager, Mar/Apr 2006
Rating : Not Yet Rated
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