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.
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).
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.