Why would you want to maintain laminar flow on a flowbench? So you could
avoid seeing what the problems are?
In practical terms, most flowbenches don't flow enough with heads that have
reasonably large ports--the pumps aren't big enough. The only reason you
wouldn't use 28 inches is because you can't get that high with the valve
open to any degree. It's only a pound of differential pressure but it takes
a lot of flow to reach that when you're sucking through a big straw. But
your premise was that this is a lot compared to the real flow (or
differential pressure) of the engine (at least I think it was) and that's
not so. At anywhere near the torque peak your engine will be flowing about
ten times that much air. Even at idle it flows more.
So there's two reasons for 28 inches (which is the standard everywhere).
It's reasonably close to the maximum that a practical bench can reach, and
you have to convert differential pressure to flow--unless your flow bench
has a handy computer built in. The math is easier if you can reach (or
convert to) 28 inches.
Of course I remember Jerry Branch had a home built flowbench that used a GMC
Blower connected to a humongous electric motor. As I recall, for some heads
he was using 15 inches of _mercury_
-----Original Message-----
From: owner-fot@Autox.Team.Net [mailto:owner-fot@Autox.Team.Net] On Behalf
Of Randall
Sent: Monday, December 06, 2004 6:54 AM
Cc: fot@Autox.Team.Net
Subject: RE: large runner 1500 (single ZS) manifold needed (longish)
> For fully developed tubulent flow, the flow is proportional to the
> square root of the pressure drop,
But isn't the whole idea to develop laminar flow, not turbulent? At the
point where it changes, there should be a fairly big discontinuity in flow
rate, no?
Avoiding turbulence is the whole reason we try to keep passages straight,
smooth changes in cross-section, etc.
Randall
|