dynamic compression only starts when the intake valve is closed, later close is less dynamic compression, static compression is based on full closed stroke of movement
Maybe I’m misunderstanding the terminology but I’ve understood with intake or exhaust valves open the compression during a compression test will be zero, even as piston move up. Only when intake and exhaust valves are closed will compression start to build within the cylinder. The point within the cylinder where the piston starts to compress the air is dependant on the valve timing.
During a comp test, I’ve understood that lots of overlap will allow the piston to move further up the piston before both valves close so the volume of air trapped within the cylinder at that point will be less than a standard factory cam without much overlap (which will trap more air volume). So big cam = less air trapped in the cylinder = lower compression.
As such, I’ve understood that compression readings during a compression test may be different for different cams (and everything else being equal).
Is this understanding wrong as I’m not sure who you were replying to.
(I’m not across dynamic compression as I haven’t looked into it in detail, but I’ve understood such needs combustion pressures and a running engine to achieve?
In any case 6% variation is a good outcome.