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2012 Chevrolet Impala

Written by PFM Staff

From the outside, the new 2012 Chevy Impala 9C1 and 9C3 police sedans are almost identical to the 2006-2011 Impala. But, what you don’t see is a much more powerful engine; a more economical and higher performance transaxle and final drive ratio combination; the bigger front brakes (and brake cooling ducts); a higher output alternator; the larger 17-inch wheels (with low profile Goodyear tires); and a police-calibrated stability control.

Over a 15-day period, we put almost 2500 miles on a 2012 police Impala 9C3 in combinations of urban calls for service, rural traffic enforcement and interstate driving. Forget what you know about the old Impala – the 2012 Impala is a whole new animal. In comparison to the old 240 hp 3.9L Impala, the performance from the new 302 hp 3.6L High Feature V6 is stunning. After all, the new 3.6L V6 Impala has the same horsepower as the 303 hp 5.3L V8 Impala SS (2006-2009) – and two more trans gears!

The new Impala is more than a second faster to 60 mph (7.5 sec) and more than four seconds faster to 100 mph (18.7 sec). The new engine also pushes the Impala to a 10 mph higher top end – an incredible 149 mph. The new Impala is 300 pounds heavier than the old Impala, which makes the improved acceleration, braking and cornering all the more remarkable.

6-Speed Trans
 
A 6-speed transaxle is new for 2012, replacing the aging 4-speed. The 6-speed does two seemingly opposite things at the same time. First, it improves acceleration. There are more gears of the properly matched ratio for the best engine performance at all vehicle speeds. Second, the 6-speed improves fuel economy. The 6-speed has two overdrive ratios instead of one.

Part of the vastly improved acceleration, of course, comes from the 70 hp stronger 3.6L HFV6 engine. However, part of it also comes from the better matched gear ratios only made possible from the 6-speed. No loss in fuel economy from a much more powerful engine? The 6-speed trans, coupled with a much lower final drive ratio (from 3.19 to 2.44) is most of the reason why.

Bigger Brakes

With a more powerful engine – and this HFV6 is a lot more powerful – the police Impala needs stronger brakes. The “whoa” has to keep up with the “go.” The most direct solution to increasing stopping power is to increase brake rotor mass. One of the most effective ways to do that is to increase the rotor diameter. The front rotors are almost an inch larger (12.7-inches) and just slightly thicker. The rear rotors are the same diameter but also slightly thicker. The overall brake upgrade is an increase in total swept area of 7%, which is a major improvement.

The final upgrade to the brakes is from a racing trick as old as NASCAR – front air ducts. The new front fascia, with the grille mesh from the Impala SS, has brake ducts to allow cool, outside air to get right into the front rotors and calipers. The result of all these brake changes is a half car-length shorter stopping distance (132.6 feet) from 60 mph with pursuit-hot brakes.

Maintenance heads-up: the front brakes on the 2012 police Impala are police-specific! The 2012 retail Impala uses the same front brakes as the 2006-2011 Impala. This is yet another way the 2012 police Impala is different from the retail version.

Larger Wheels

Larger diameter front rotors require larger diameter wheels. The older 16-inch steel wheels have been bumped to 17-inches. The front rotor change also means the old 16-inch Impala wheels will not fit over the new Impala’s front brakes. OK…the old 16-inch wheels will fit on the rear of the new Impala – but don’t do it! The differences in section width and aspect ratio between a 60-series, 16-inch tire on the rear and a 55-series, 17-inch tire on the front will result in a tendency to oversteer. Don’t try to outsmart the stability control.

A larger wheel also means a new pursuit-capable tire had to be developed. With universal acclaim, the Pirelli P6 Four Seasons has been replaced by the Goodyear Eagle RS-A. Increasing the wheel diameter lowers the sidewall, so a 55-series tire replaces the 60-series tire. That change alone increases steering responsiveness. The new Impala is more nimble and much quicker to respond to accident avoidance maneuvers and sudden lane changes.

Police-spec StabiliTrak

The last of the hidden improvements to the 2012 police Impala is StabiliTrak, GM’s version of electronic stability control. The Impala 9C1/9C3 now comes standard with stability control. Required by federal law, StabiliTrak has been standard on the retail Impala since 2008.

The “default” mode for StabiliTrak on the police Impala – the setting when the ignition key is turned on – has the same parameters as used in the retail Impala.

Push the StabiliTrak button once, and it is in "performance mode." Like the performance mode in the Caprice PPV and Tahoe PPV, this mode is tuned for pursuit driving, and is not available on the retail Impala.

Push and hold the button for 5 seconds and the traction control feature is turned off and the StabiliTrak parameters are opened up even more, just like can be done on the retail Impala. This doesn’t turn StabiliTrak OFF, instead, it opens up the parameters for delayed engagement of the electronic controls.

The entire time we spent in the police Impala on patrol, we drove in default mode – even during dedicated traffic enforcement and many hard U-turns followed by heavy acceleration. We found the default mode to be just fine even for very aggressive traffic work.
 
Upfitting

As for upfitting the new Impala, the interior and interior dimensions are virtually unchanged. The emergency and communications gear taken out of the 2006-2011 Impala will fit the 2012 Impala…prisoner partitions, push bumpers, center consoles. The front seat and rear seat dimensions are unchanged from the outgoing Impala. The trunk volume is identical. The big change for upfitters on the 2012 Impala 9C1 is an upgrade from a 150 amp alternator to a 170 amp alternator.

Track and Road

A much more powerful engine, a wider selection of trans gears, bigger brakes, lower profile tires and a police-calibrated stability control all add up to a much faster sedan around the road course. The 3.6L HFV6 Impala is more than three seconds faster around a 2-mile road racing course than the old 3.9L V6 Impala. That is a whopping 21 car-lengths ahead of the 3.9L Impala.

You don’t have to be on a race track or EVOC course to feel this performance. You see it right away in the normal “brake, U-turn and accelerate” of traffic enforcement. Same for entrance and exit ramps. Same for merge into traffic. Same for tight but fast maneuvers in a heavily urban scenario.

Gas Mileage Unchanged

While the 3.6L HFV6 powertrain has almost 70 hp more than the outgoing 3.9L V6, the new engine and 6-speed trans combination is also slightly more fuel efficient. As a result, while both engines have the same EPA City rating (17 mpg), the new drivetrain has a 4 mpg higher Highway estimate (28 mpg). The EPA Combined rating for these engines is 20 mpg (3.9L V6) and 21 mpg (3.6L HFV6).

In practical terms, your officers will get exactly the same fuel economy from the new Impala as the old Impala – from a MUCH higher performance sedan. For rural and highway use, the 3.6L Impala is a high-speed hot rod…a blast to drive. It has great acceleration, responsive high-speed handling and excellent brakes. For urban and suburban use, the new Impala has lots of low end torque, and is quite nimble. Short of making the Impala a bit roomier on the inside, the 2012 police Impala is better in every way that counts. Think Impala SS…really.

(SIDEBAR)

3.6L SIDI HFV6 (LFX)

 

The newest Chevy police engine is their 3.6L High Feature V6, HFV6. This is a seriously different engine from their otherwise credible High Value 3.9L V6 engine used in the 2006-2011 police Impalas. The High Value V6 engine dates back to 2004. These were the first cam-in-block, pushrod, overhead valve (OHV) engines to feature Variable Valve Timing. That was a huge technology breakthrough. The 3.9L V6 used in the 2006-2011 police Impala 9C1varied between 230 and 240 hp and between 235 and 240 lb-ft. of torque.

 

VVT changes the timing between the cams and the crank. VVT advances the timing at low engine rpm for the most torque and retards the timing at high engine speeds for the most horsepower. For 2007, the High Value V6 was upgraded to Active Fuel Management, GM’s version of cylinder deactivation, formerly known as Displacement on Demand. Under engine light loads, three of the six cylinders are shut off from fuel and air, improving fuel economy. For 2008, this High Valve V6 became a flex fuel engine, rated to run on E85.

 

High Feature V6

While the 3.9L V6 was an overhead valve (OHV) engine, the new 3.6L HFV6 is a double overhead cam (DOHC) engine. The HFV6 family of engines is the result of a joint effort between Cadillac engineers in Detroit, Holden engineers in Australia, and Opel engineers in Germany. This 3.6L V6 is produced in Flint, MI, Port Melbourne, Australia and St. Catherines, Canada. The HFV6 is a new family of engine, however, this is not the first year for the 3.6L HFV6. In fact, it was introduced on the 2004 Cadillac CTS.

 

Significantly, the 3.6L HFV6 has been used in the Holden Commodore and Holden Statesman since 2004. The 2011 Chevy Caprice PPV is produced at the same Holden plant in New South Wales as the Commodore and Statesman. The Aussie cops have already put lots of patrol miles on the 3.6L HFV6 in their big sedans long before its 2012 debut in the Chevy Caprice PPV and Impala 9C1. In fact, some police fleet managers may have already seen the 3.6L HFV6. This has been used in the Chevy Malibu since 2008.

 

Lower horsepower versions of the HFV6 have variable cam timing on only the intake cam. The higher horsepower versions – like the one in the 2012 Caprice PPV and Impala 9C1 – have variable cam (valve) timing on both the intake and exhaust cams. The cams can be rotated between 15 degrees advanced (ahead) of Top Dead Center 45 degrees retarded (behind) TDC.

 

The first version of the 3.6L HFV6 engine with double overhead cams and variable valve timing was a capable, if pedestrian, engine. In LY7 (retail) trim, this 3.6L V6 produced 255 to 264 hp compared to the LGD (police) version of the 3.9L V6 at 233 hp. What put this HFV6 on the map was direct injection (DI).

 

Direct Injection

Spark Ignition Direct Injection (SIDI) pushed the 3.6L HFV6 to between 302 hp (Cadillac STS) and 312 hp (Chevy Camaro). This 3.6L SIDI V6 in the police Caprice and police Impala produces 301 hp and 302 hp, respectively.

 

Compared to standard engines of the same displacement, direct injection produces 15% more horsepower, 8% more torque and 3% better fuel economy. Direct injection is a clear improvement over standard fuel injection.

 

With direct injection, gasoline from a common rail fuel line, under extremely high pressure, is injected directly into the combustion chamber. With multi-port fuel injection, gas is injected into the intake manifold or cylinder port. The more precise control over the fuel from direct injection allows much higher compression and means a more complete burn-more power, more torque, better fuel economy, fewer emissions.

 

Direct injection is not new. The first production gasoline direct injected engine (Mitsubishi) appeared in 1996. GM’s first direct injected engine was the 2004 2.2L I4 used in the German Opel and British Vauxhall. The first domestic GM direct injected engine was the 2.0L I4 in the 2005 Pontiac Solstice. The LLT 3.6L HFV6 was upgraded to direct injection for the 2008 Cadillac CTS and STS. The point? The same basic 3.6L HFV6 used in the 2012 police Caprice and police Impala has already been a retail engine for four years.

 

Police 3.6L HFV6

For 2012, General Motors tweaked the 3.6L HFV6 a bit. The (essentially) Gen3 version is 20 pounds lighter thanks to a redesigned cylinder head, which now includes an integrated exhaust manifold. The intake manifold, fuel injectors, intake valves and fuel pump have also been upgraded on this four year old engine. The intake port has been redesigned for better flow, the intake valves are now larger and the intake cams have a longer duration opening for the valves. The more air in, the more power.

 

The Holden Commodore, which is essentially the police Caprice, has had this 3.6L SIDI HFV6 since the 2010 model year. Holden (GM of Australia) is the “performance” division of GM Australia, much like Pontiac had the “we build excitement” reputation in the U.S. That Holden engineers took the lead in SIDI engine development is a very good thing.

 

This LFX 3.6L HFV6 is used in the 2012 police Caprice, police Impala, Cadillac CTS and SRX and Chevy Camaro. The 2012 LFX V6 is about 10 to 15 hp more powerful than the earlier LLT 3.6L HFV6. In addition to more power, and just slightly more torque, the new LFX-version of the 3.6L HFV6 produces its peak torque at a lower rpm than the LLT version. Torque wins drag races, and DOHC engines typically need to rev up a lot before they hit peak torque.

 

Overall? The 302 hp 3.6L HFV6 in the police Impala makes it a LOT faster than the outgoing 3.9L V6, while giving better mileage under highway conditions. And the 301 hp 3.6L HFV6 in the police Caprice makes it a LOT faster than the 250 hp 4.6L Ford CVPI, in a sedan of the same size, along with better fuel economy. Finally, the 3.6L SIDI HFV6 is not a “new” engine; this is not its “first” year. In direct injection (SIDI) form, this 3.6L engine has been in the Caprice-like Holden Commodore used by the Aussie police for two years.





Published in Police Fleet Manager, Jan/Feb 2012

Rating : 8.0


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