The Coyote engine relies on variable cam control to help it make power, and improve drivability. Ever since this engine was released however, there have been many who have “locked out” the VCT (variable cam timing) system in order to run aftermarket cams. As the engine has aged, and manufacturers have learned more about it, many are finding that locking out the cams is not always the best strategy.
The Coyote VCT system works by moving high pressure oil into a camshaft phaser, allowing the camshaft to be advanced or retarded during engine operation. Oil flow to the phaser is controlled by VCT solenoids, and commanded by the computer. The lockout devices often used for blocking the VCT typically limit the movement of the phaser, thus locking out its operation. Initially, when VCT was introduced on the 3-valve 4.6 and later on the 4-valve Coyote, there were few if any aftermarket engine management systems capable of controlling the Ford VCT system, especially when it came to controlling 4 camshafts.
AEM’s Infinity system was one of the first on the market that could control the Coyote’s VCT system. We used it last year on our Carb Coyote Cobra Jet build, and showed how effective it is when we made right at 2 hp per cubic inch, utilizing the VCT system, and tuning the engine with Infinity. This system is quickly becoming a favorite of a variety of racers and enthusiasts with hardcore builds, who need a powerful tuning element.
Some argue that the VCT system is just one more element of complexity from both a mechanical, and a tuning standpoint, and is not really necessary to overall Coyote engine performance. While, in extremely high RPM applications the VCT system is less effective, as we showed in our Carb Coyote Cobra Jet series, in the RPM range where these engines spend most of their time it’s vital.
AEM recently set out to show just how much power Coyote owners may be leaving on the table without the use of VCT. To do that, they tested a stock Coyote engine without VCT control, then began adding VCT first to the intake, then to the exhaust cams.
The testing conducted by AEM proves how vital the VCT system is. With no VCT, the Coyote engine peaks out at 6,500 RPM making 423.1 hp. With the intake only VCT, the engine only picks up 5.8 peak horsepower jumping to 428.9 hp at the same 6,500 RPM. With the exhaust VCT also activated, the engine puts out 465.4 hp at 6,500 RPM. This is where carefully studying the dyno information is valuable. A total gain at peak RPM of 42.3 hp might not sound like its worth the trouble of the VCT, but closer inspection shows a much bigger story. At 3,900 RPM the engine is making 109.3 hp more with the VCT activated than it was without.
The story is very similar, and perhaps even more dramatic in terms of torque. With no VCT the engine made 368.6 lb-ft at 5,400 RPM. With the intake VCT active, that torque jumps to a peak of 412.2 lb-ft, and the peak drops down to 4,400 RPM, torque stays above 400 lb-ft until nearly 5,400 RPM. Activating the VCT on the exhaust cam shows another substantial spike in peak torque output, taking total peak torque to 454.4 lb-ft at 4,400 RPM. That’s a gain of 85.8 lb-ft, at peak.
Once again with torque, the graph proves out how valuable the VCT is for torque as well. Take a look at the torque graph at 3,700 RPM. At that point we can see that with VCT, the Coyote engine is making another 149.9 lb-ft than without. Even at the horsepower peak of 6,500 RPM, torque with VCT active is still outrunning torque with it deactivated, with the engine making over 375 lb-ft at 6,500 RPM. The non VCT setup never outmatches the VCT activated setup for torque or horsepower, especially below peak where it matters the most.
This is the type of research we enjoy looking at, and we’re glad AEM took the time and effort to conduct it. These numbers, and this information should be something every enthusiast with a Coyote engine keep in mind when setting up camshafts for their engine, and tuning electronic tuning methods.