Thanks John; when I build a tester for myself, I think I'll include
a provision to allow varying the orifice diameter unless I can find
out that there is some "standard". Hmmmm, maybe I'll borrow a
"Snap-On" and measure the orifice.
> From: R. John Lye
> >I've seen a diagram, I see that the air supply pressure bleeds
> >through a small orifice on the way to the engine cylinder and that
> >the pressure of the "supply" is compared to the pressure of the
> >cylinder to arrive at the percent of leakdown but:
> Yup, that's about it.
> >won't the orifice size affect the amount of air available to
> Sorta - if there's little to no leak, a larger orifice will just
> allow the system to stabilize faster. If there's a big leak, a
> larger orifice will make it easier to hear where its coming from
> <grin>. What you need to keep in mind is that you're measuring
> pressures, not volumes of air.
> >Is it just arbitrary?
> Its not arbitrary, but it is relative; that is, the pressure in
> the cylinder has some relation to the pressure in the supply
> side which is determined by the relative sizes of the orifice
> in the tester and the size of the leak.