Dual pattern cams...Black Magic or Legit?

[eschaider]

I think the reason this type of camshaft helps in a true race application is it allows the four middle cylinders to run at AFRs that more closely approximate the four corner cylinders, thereby providing a better AFR or lambda behavior on track. That may (I don't know) translate into better race mileage because those cylinders no longer run as rich as before.

One of the immutable facts, or as I like to call them, universal truths, is that a cylinder with a compromised (doesn't matter how it happened) air inlet will always produce less power than the same cylinder with an optimized air inlet, other metrics being equal — always there are no exceptions.

Now someone is going to say, "yeah, but what if I give it a squirt of nitrous?" The moment you do that (or anything similar), the whole game changes. More importantly, the racing association rules prohibit it, and the PITA rules of street car design, building, and operation significantly discourage it — so we shouldn't go there either.

If the cylinder ingests less air because the inlet is compromised compared to the other inlets that cylinder will produce less power. As luck would have it, it takes 10 lbs of air per minute (in round numbers) to make 100 FWHP. If the compromised port can only process 9 lbs of air per minute, it will only make 90 FWHP no more, no matter what, nitrous style enhancements excluded.

If stretching or reducing cam duration can move that additional air to bring that cylinder back to 10 lbs of air per minute, then that begs the question, why did you not further optimize the cam profile for the cylinders with the good ports and make even more power — this is after all a race engine reaching for optimum power. The answer is it is not possible (those universal truths things again). You might be able to clean up the AFR and improve fuel consumption but that is about it. The cylinders hampered by less effective runner architecture will continue to be wimpy powerwise.

You can not tune horsepower back into a cylinder that is being choked off for air. It is impossible without using something like nitrous to add the additional oxygen necessary to burn the fuel.