Join Date: Jul 2017
Location: Nobel Ontario Canada
Bullitt Year: 08
Bullitt Color: DHG
Bullitt Serialized Number: 4404
Variable Cam Timing. Performance and lower Emissions
Variable Camshaft Timing was developed by Ford, and first made it's appearance in the late 90's 2.0 Zetec engine. The early versions were either on the Intake cam, (improved performance) or the Exhaust cam, (reduced emissions.) The 2008 Bullit has variable cam timing, but since it is a SOHC, the effects on performance and emissions are a compromise. Variable cam timing traditionally operates with oil pressure driven cam phasing controlled by solenoids and the PCM adjusting for factors such as load and RPM. The disadvantage of early systems was the need for higher oil pressure and the resultant parasitic losses.
With the advent of the Coyote engine Twin independent Variable Camshaft Timing or Ti-VCT came into production. This new system provided the ability to advance or retard both the intake and exhaust cams independently. This provides greatly improved performance and lowered emissions, eliminating the EGR completely. The use of Borg Warner's Cam torque actuation (CTA), which uses torsional energy in the valve train to rotate the camshaft instead of traditional oil pressure driven cam phasing was also introduced.
Basically, there is a center lock position with oil pockets on each side and check valves. The phaser directs ratcheting advance or retard (based on load and RPM and...) and the oil pockets stabilize the movement in only one direction at a time aided by the check valves. So the oil pockets act as limiters but do not move the cam timing. The torsional energy of the cams rotation cause movement, and the phaser returns to center lock position for "cruising" operation. This system operates at lower oil pressures because the oil is not driving the timing changes. And, intake and exhaust cams can change timing independently to optimize performance and emissions. There's lots going on here and it requires a lot of computer power to bring harmony to it's operation.
The result of all this technology has taken the 4.6's horsepower of 315 all the way up to 480 HP in the 2019 Gen 3 Bullit Coyote.
What's next? Just read an interesting article on Microwave ignition, which they claim can add 30% more power and reduce emissions by 80%! Wonder if you'll be able to heat up your lunch as well?
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In my defense, I was left unsupervised.