Dual pattern cams...Black Magic or Legit?

[Buddy Rawls]

“The significant issue here is that the lobe gymnastics do not fix the problem of differing power delivery from different cylinders. The OP accurately identified the phenomenon as resulting from varying cylinder-to-cylinder inlet manifold passage flow dynamics. If the problem is optimizing and normalizing cylinder power, the solution is absolutely not multi-profile cams“

The whole purpose of the original post was questioning what is special regarding the 4 pattern cams. The design basically uses differing valve events for the inner cylinders and for the end cylinders. The question was posed, Is it snake oil or legitimate? Flow differences from cylinder to cylinder when used on an open plenum intake that different port lengths (and flow and velocities) is where valve events that match the cylinders flow parameters do their work. But the valve events have to be right.

Your statement about lobe gymnastics not being able to fix flow problems is where we differ. As an engine modeler, I developed my valve event calculations in the 90’s and have been doing custom cams for 25 yrs. The doors (valve events and ramp rates) into and out of the cylinder are critically important. And the valve events and ramp rates are critically linked to the the flow parameters. Valve events can crutch short comings (restrictions, high velocities, or poor flow regions) as well as truncate the activity of over abundant huge cross-sections and low velocities. A camshaft is not a globally characterized component, although everyone tries to make it work like that. Given same cid geometry, the behavior of 270 degrees duration (for example) on large cross section inlet ports is drastically different than on a small cross section high velocity scenario. The exhaust positioning requirements vary greatly between the two as well.

Applying this to the multi patterned camshafts, in a situation of different flow parameters might look like: Cylinder A needs valve events that calculate to 270 deg seat duration on the intake on a 108 centerline. The exhaust might be 273 deg on a 113 centerline. Cylinder B with different flow might need 272 on a 107.5 intake and 273 on 112. These are a simplified look at the sort of differences that valve events tailored cylinder to cylinder might look like. Grinding such a cam would be a pita. Using an OTS 4 pattern cam, that may or may not match the needs of the motor’s flows is no diff event than any incorrect cam, except it has some good buzzwords along with it. Wrong is wrong. Correct is correct, and it can be thought of like a bell curve. Perfection with the airflow has some tolerance for sure.

Totally equal cross-sections and lengths exhibit very similar, if not equal flow parameters. And small differences can be perfected by the A/F delivery. But this does not change air flow thru the motor. This is utilizing what flow characteristics the cylinders have and optimizing A/F.

To me, it seems like you look at the A/F as the equalizer and power maker. I look at the engine flow parameters (controlled by the valve events) as the power maker, with A/F being a tuning tool to optimize thru the range.