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PROVEN 3.6L SIDI HFV6 (LFX) T he newest Chevy police engine is their 3.6L High Feature V6 HFV6. Tis is a seriously different engine from the 3.9L High Value V6 engine used in the 2006- 2011 police Impalas. While the 3.9L V6 was an overhead valve (OHV) engine producing about 233 hp, the new 3.6L HFV6 is a double-overhead cam (DOHC) engine producing 301 hp in the Caprice. Te 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. Tis 3.6L V6 is produced in Flint, Mich.; Port Melbourne, Australia; and St. Catherines, Canada. Te HFV6 is a new family of engines; 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 also been used in the Holden Commodore and Holden Statesman since 2004. Te Aussie cops have already put lots of patrol miles on the 3.6L HFV6 in their big se- dans long before its 2012 debut in the Chevy Caprice PPV and Impala 9C1. Higher horsepower versions of this 3.6L HFV6 have variable valve timing (VVT) on both the intake and exhaust cams. VVT changes the timing between the cams and the crank depending on the throttle. In the most general terms, VVT advances the timing at low engine rpm for the most torque and retards the timing at high engine speeds for the most horsepower. Te cams can be rotated between 15 degrees advanced (ahead) of Top Dead Center 45 degrees retarded (behind) TDC. Direct Injection What really put this HFV6 on the map was direct injection. Spark Ignition Direct In- jection (SIDI) pushed the 3.6L HFV6 to between 301 hp (Chevy Caprice) and 312 hp (Chevy Camaro). Compared to standard engines of the same displacement, direct injection produces 15 percent more horsepower, 8 percent more torque, and 3 percent 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 injec- tion, gas is injected into the intake manifold or cylin- der port. Te more precise control over the fuel from direct injection allows much higher compression and means a more complete burn, i.e., more power, more torque, better fuel economy, fewer emissions. Police 3.6L HFV6 For 2012, General Motors tweaked the 3.6L HFV6 a bit. Te Gen3 version is 20 pounds lighter thanks to a redesigned cylinder head, which now includes an integrated exhaust manifold. Te intake manifold, fuel injectors, intake valves and fuel pump have also been upgraded on this 4-year-old engine. Te intake port has been redesigned for better flow, the intake valves are now larger, and the intake cams have a lon- ger duration opening for the valves. Te more air in, the more power. Tis 3.6L HFV6 (LFX) is about 10 to 15 hp more powerful than the earlier 3.6L HFV6 (LLT). In addi- tion 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. Finally, the 3.6L SIDI HFV6 is not a "new" engine; this is not its "first" year. Te Holden Commodore, which is the Aussie police Caprice, has had this 3.6L SIDI HFV6 since the 2010 model year. S Half of the better throttle response from the Caprice V6 compared to the Ford CVPI is from the additional 50 hp. The other half is the two additional gears from this excellent 6-speed trans. speeds – low-end, mid-range, high-speed. Why? Te Caprice has 50 hp more than the CVPI and has two more transmission gears. Whether accelerating from a U-turn or accelerating to pass, or accelerating to reach 100+mph speeds, the Caprice does it with less throttle than the CVPI. One area of the Caprice V6 performance especially stands out. Under full throttle, the Ford CVPI has an infamous flat spot be- tween 65 mph and 85 mph. Tanks to the 6-speed in the Caprice (versus the 4-speed S New for 2012, the Caprice gets the same 3.6L "High Feature" V6 used in the Camaro and Cadillac. This Holden (GM of Australia) developed 3.6L engine has already seen two years of police service Down Under. www.pfmmag.com 29