Good article, Grant. Yes, dynamic CR is extremely critical. Because that is what is determining actual cylinder pressure. Static CR gives you a way to compare apples to apples, but once the camshaft profile is introduced into the equation, you're comparing apples to oranges.
As camshaft profiles move increasingly larger, particularly with later closing intake valves, cylinder pressure will be reduced by default. As cylinder pressure goes away, the ability to convert fuel to heat will correspondingly decrease. Less heat = less power. The only way to increase cylinder pressure is to raise static CR.
If you go the other way and try to run a lot of static CR with a fairly small and tame cam profile, cylinder pressure will be way too high.
Your blower combination is a beast of a different color, but with a naturally-aspirated motor, cranking compression numbers will generally be fairly close, no matter if it is a car on a dealership floor, a drag car or an oval track car. You would think a drag car with 16:1+ static CR would have really high numbers, but the big camshaft pulls cylinder pressures back. The car sitting in the showroom has very low static CR, but the camshaft gets the intake valve closed early, which lets the engine build more cylinder pressure.
Back a century or two ago, we were at the race track and tuning a pig. We had a fairly new combination with a different camshaft profile than we normally ran. To top it off, we were running more altitude that we normally ran. And we were lost. Out came the trusty compression tester and we started rolling the cam around, trying to find the highest compression numbers. And can you imagine, the car actually started running.
A lot of cam manufacturers will end up with a late-closing intake valve. They're trying to use the exhaust pulse wave to help with cylinder fill, for one. Second, they're dealing with a larger valve than on the exhaust side. Bigger valves mean more mass. More mass means inertia. So they will try to be lazy about bringing the intake valve back to the seat, to keep it from bouncing. Late closing intake valves mean the pistons are already moving up in the cylinder. And for every degree of rotation the intake valve is still open, that is more cylinder pressure being sacrificed. Ever seen an motor that had sooty intake ports? That motor was an excellent example of a poor camshaft/static CR mix.
As for your E3 plugs, I would drop them in the nearest trash bin and go back to a regular plug. The whole E3 advertising campaign is reminiscent of the old Split-Fire plugs, defined in three words. Snake. Oil. Medicine.
There is one, only one, no more than one and I repeat, just one way to make power with a spark plug. Run enough ignition system to allow you to open up the plug gaps. Full stop. Once you have a plug of the correct heat range to live in the given cylinder, you can run a Champion, AC, Autolite and never see spit's difference between any of them. On the dyno, or at the racetrack. But you can open up the plug gap and expose more of the plug's flame kernel to the fuel-filled cylinder. The E3 plug goes directly back against that fact, as they end up caging the kernel with additional side electrodes.
In most instances, we needed to index spark plugs in the race motors to get the side electrode clear of the piston dome. But when we would get the side electrodes up at the top of the chamber, that also exposed the flame kernel as much as possible. If you can open up the plug gap a bit, you create a larger kernel.
We made up a test block we could thread 8 spark plugs into and used as many different plugs as possible. We would stick a distributor into the machine, put a cap and plug wires on it and run the wires to the plugs in our test block. Shut out the lights in the room and start the machine. The brightest light in the block is the best plug you can use, because it will have the largest kernel and the best shot at creating a good flame front. Anyone remember when the Bosch platinum plugs were the bee's knees? They had tiny, needle-like, center electrodes and the flame kernel was just as tiny. And, as you might imagine, they didn't perform nearly as well as regular plugs.
I always preferred to use Champion plugs, because of the cad-plated shells. It makes the plug much easier to read for heat, as the heat ring will be more evident. All the fancy business with magnifying lights will get you close when you're looking for 'pepper' on the porcelain, but once you've checked that, the outside of the shell is what you want to be looking at. As a matter of fact, if the ignition system is hot enough to do a good job, trying to read the plugs for color goes out the window, because they will all look white.
Plugs on a street motor are extremely hard to read, because you end up with so much idle time. You can have a plug take on a lot of color at idle and never clean up enough to show you what conditions are like under power. But then you always get the Einsteins that sit at a light, revving the motor, just "to keep the plugs clean". :rofl:
