Here is a short history of the little engine that saved Ford. Overhead cam design moved the "cam", the mechanisms that drives the valve and pistons within the cylinder heads, above the combustion chambers, instead of below. While the mechanism is somewhat more complex, it makes the combustion more efficient by injecting more directly, and the overall reciprocating portions of the engine is less and thus less vibration is generated. Double Overhead Cam uses two separate cams per bank of cylinders, one for intake and one for exhaust. The original Duratec was a 2.5L V6, now known as Duratec 25. Introduce in 1994 for the 1995 Mondeo, it is a 2544 cc 60 degree V6. For a V6, it is a very small one, esp. Ford, but it is a very high tech engine for the time. It has double overhead cam (DOHC) and 4 valves per cylinder, generating 160 HP. For a V6, it can go to quite high RPMs: 6750 RPM is the redline. It was used in the first generation Ford Mondeo (i.e. Ford Contour / Mercury Mystique in the US), and later, Jaguar X-Type (based on Ford Mondeo) and Mercury Cougar (coupe based on Mondeo platform).
Later the SVT version of the engine was improved to 200 hp without any sort of forced induction, or boring out the cylinders, or otherwise play with the dimensions. It was only available in the Ford Contour SVT, sometimes touted as "poor man's BMW M3". Mazda also use the same engine, but slightly smaller displacement (2.49L) in order to avoid the Japanese 2.5L tax. Variable Valve Timing, often abbreviated as VVT is a technology that allows the lift, duration, or timing of the valves to be adjusted while the engine is in operation. It could only affect the intake valves, or both intake and exhaust valves. It improves efficiency of combustion. The 3.0L version of Duratec is the same engine as the 2.5L version, but have a larger bore, so the displacement is now 2944 cc. Regular version produces 201 HP, and was used in Taurus / Sable / Escape. An upscale version for Lincoln LS and Jaguar S-Type produce 232 HP. In 2004, a slightly modified version of Duratec 3.0L was used in the Five Hundred, which later was revised into the new Ford Taurus.
In 2006, the new Ford Fusion / Mercury Milan / Lincoln Zephyr got a revised version of Duratec 3.0L V6, now with variable valve timing. Latest version of this engine now produces 240 HP. Two other minor revisions of this engine was produced for European markets. In 2006, Ford introduced a new engine series under codename Cyclone, but marketed as Duratec. It is produced in the Lima, Ohio in the Ford engine plant there. Mazda uses the same engine under MZI name. The Duratec 3.7 is the 3.5 but bored out slightly to make it 3721 cc. This results in 273hp output. For 2010, Ford introduced a version of this engine for the Mustang, with Twin Independent Variable Cam Timing (both intake and exhaust) or Ti-VCT, resulting in 305 hp and still achieving 31 mpg highway. The redline is 7000 RPM. The first vehicle to use this was the 2011 Mustang, replacing the ancient "Cologne" V6 (which was produced since the 1960s!) The new Duratec 3.7 virtually matches the V8 engine output of 2010 Mustang.
Also, 305 HP was what Mustang Cobra SVT V8 made in 1995, the hottest version of Mustang then available. Now it's the output of the base engine. The "EcoBoost" engine is a twin-turbo version of Duratec 3.5 engine, used in the new Ford Taurus SHO (see below) and may be available in some top-of-line vehicles. Both Duratec 35 and Duratec 37 are used in many Ford and Mazda vehicles, from Mazda CX-9 crossover to Ford F-150, as well as Ford Flex, Ford Edge and other vehicles. EcoBoost V6 engine is a twin-turbocharged version of Duratec 35, used in the new Ford Taurus SHO, Lincoln MKS, MKT, and Ford Flex, and new for 2011, Ford F-150 pickup. Originally it was dubbed "TwinForce", in a Lincoln prototype, but the name was later changed to EcoBoost. The EcoBoost V6 used 2 Garrett T15 turbochargers that generate up to 12 PSI of boost, making it use up to 25% more air than normal, and direct gasoline fuel injection into the cylinder instead of any premixing. As a result, it generates 365 HP with regular unleaded gas, and still delivers 25 mpg highway.
The EcoBoost concept is to provide the power of a much larger engine, such as a 6.0L V8, without consuming more fuel. The concept was successful that the engine received "Ward's Top 10 Engines 2010", and the concept is being pushed out to other Ford Duratec engines as well. EcoBoost I4 has already been demonstrated. For more information on EcoBoost engines, see wikipedia: Ecoboost. In an "interference engine" the cylinder head can hit the valves while the valve is "open" because the valves "pop" into the cylinder. In normal operation, this would never happen because the the cams would keep everything synchronized. However, should a catastrophic failure of the chain that keeps the cams synchronized occur, or if the camshaft breaks, the result is destroyed valves and complete engine failure. Many smaller engines use "interference design" as it is more efficient and achieves higher compression. The original Ford SHO has a specially built Ford/Yamaha V6 for the power.
