CIS airflow meter limits HP? (Martin Pajak)

[Bruce Bell]

OK, How about some simple numbers.

The airflow plate on every (5 cyl.) Audi I've seen is 80 mm in Dia. This
plate moves within a cone in the air meter. so flow must come from the area
between the plate and the wall of the cone. I'm going to guess there is
around 10 mm clearance between the plate and the cone wall after the plate
has risen within the cone. I'll  leave it to someone else to get an actual
measure as I'm much too lazy to pull the boot tonight. So, we now have a
circle (cone dia.) of .06847 square ft. and from that we subtract the area
of the plate at .05411 sf. and we find a flow area of .0143 sf.

Looking at Master Corky, page 61, where he suggests max velocity not to
exceed is 450 fps we have a velocity number and 450 * .0143 * 60 sec = 386.1
cfm or enough for about 257 hp. Now, anyone who has looked at enough of
those cones knows very well that they come in different shapes. so if we
increase my assumed 10 mm by just two more for a total of 12 then we have a
flow are of .01744 sf. or enough to flow 470.9 cam or about 313 hp.

The question is, how much flow area is there... never mind I just got off my
a** and measured the Urq. 80 mm sensor plate 13 mm clearance on short side
and ~23 mm on the big side for an average of 18 mm for the flow area around
the circumference of the plate. This computes to 731.2 cfm or ~486 hp.  If
you drop the velocity to a conservative 300 fps there is still nearly 500
cfm or enough to easily clear 325 hp.

I'll leave the issue of enough fuel to someone else...

Bruce