This Wegner Spec engine, used...
This Wegner Spec engine, used in selected NASCAR Series, is based on the General Motors LS engine platform. Comp Cams is aggressively pursuing development of a variable valve timing package for this engine family.
In order to set a stage for what follows, let's first revisit some of the fundamentals involved in how valve timing relates to power output. And to further clarify how "power" is defined in the context of this story, let's simply say horsepower is a mathematical function of torque which, in essence, is closely related to volumetric efficiency. Increase volumetric efficiency at any point in an engine's rpm span, and at least the potential for a torque gain will result.
Relative to how valve timing plays into volumetric efficiency, let's further say the designed ability of a camshaft to "time" intake and exhaust valve events (particularly as they relate to piston/crankshaft position) is key to achieving proper volumetric efficiencies. For example, when a given piston is at or near maximum downward speed during an inlet cycle, you'd like for intake valve event to support a high level of volumetric efficiency. And, in a similar fashion, other piston motion patterns should be accompanied by valve action that helps optimize cylinder evacuation during the exhaust cycle.
The cam phaser kit is supplied...
The cam phaser kit is supplied (as provided for the Ford applications) complete with special tools for disassembly of the stock components and phaser limiter plates and detailed instructions for re-assembly and a guidance on subsequent engine tuning.
Historically and largely because camshafts are characterized by a "fixed" design, we've only been able to advance or retard their installed orientation to an engine's crankshaft. We were limited to the amount of "variability" achievable, relative to where in the rpm range valve timing plays into volumetric efficiency. Simply stated, we "advance" cams to enhance lower rpm torque output and "retard" them (both in relationship to the crankshaft or piston position) for higher rpm output. Ideally, at least from one perspective and outside the realm of a fully-computerized valve train with true valve timing variability, it is plausible to provide some means for advancing and retarding the camshaft during engine operation.
By the employment of "cam phasers," it's possible to find a middle ground between either advancing or retarding a cam. What this means is that while advancing and retarding a given camshaft won't necessarily boost (or even shift) peak torque values, it's now possible to increase torque below and above this point. In essence, the overall torque curve becomes "flatter" (or wider) over a broader range of engine speed. (See graphical illustrations of torque curves with and without phased camshafts on the next page.)
These specially-engineered components are designed to limit the amount of camshaft positioning (phasing) available, thereby allowing for more "creativity" in producing cams that take advantage of this technology, providing torque gains above and below peak torque rpm.
Actually, as an outgrowth of Ford's introduction of computer-controlled cam gears on its '05 modular, Three-Valve engines for Mustangs, Comp has used this technology platform for further improvements. Ford's approach allows the cams in these engines to include a range from 20-60 degrees retard during part-throttle operation, thereby reducing friction horsepower and enhancing fuel economy. Based on the use of their computer-controlled camshaft phasers and regardless of engine speed, this approach enables camshaft positioning for optimal power throughout the rpm range. The net result is an extended power range.
Using a specific routing of engine oil through cylinder heads and camshafts, the on-board computer regulates a pair of solenoids which, in turn, control the phasing of the camshafts. The span of control can be as much as 60 degrees of camshaft retard. As you would expect, the extent and precision to when the cams undergo a phase change is a function of the software written into this portion of the onboard computer. Stated another way, there appears be a way to provide valve timing (camshaft design) that takes further advantage of this technology, enabling a window for exploring this concept in other engines and applications.
As produced by Ford, their "stock" phasers provide such a wide range of camshaft retard (up to 60 degrees, as stated), there are limitations based on the amount of available piston-to-valve clearance. As a result, there are corresponding limits that are placed on what can be done with non-stock camshafts, certainly in the areas of net valve lift and valve overlap periods. Also keep in mind that Ford is faced with certain compromises, including exhaust emissions and Federal fuel economy mandates, which further restrict the extent to which they can focus on power output. Such is not the case when you apply this technology to engines in a racing environment.