Factory Pro Velocity Stacks work primarily by increasing the engine's dynamic compression - kind of like milling the cylinder head or slightly higher compression pistons over a range of desired rpm ranges. Increasing compression doesn't require big fuel changes.
Dynamic compression is different from cranking compression. Dynamic compression is essentially cranking compression + extra air that gets trapped in the combustion chamber as a result of proper intake tract (velocity stack) length, intake cam closing and also the effects of the exhaust systems in a RUNNING engine.
Dynamic compression effects are also related to rpm ranges - as intake ram charging; commonly occurs strongest over a 3000 to 3500 rpm range. (usually....)
Can you get less dynamic compression than cranking compression under running conditions? Yes. If the resonant frequencies of the intake or exhaust systems are wrong, the systems can yank air back out of the combustion chamber before the intake valve closes (and you'd call that a "flat spot) |
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