CIS airflow meter limits HP?

[JShadzi at aol.com]

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[ Picked text/plain from multipart/alternative ]
Bruce, while the simple formulation is an interesting reference point, to
have any real idea of how much the airflow unit can actually flow, we'd have
to not only run some air through it on a flow bench, but also pressurize the
fuel dist to ensure proper control pressure is being enacted.  Also, with the
proper airboot in place, etc.

My BTDT just doesn't support those kind of power levels (though I'd love to
believe it), at one point I was running 5 EFI injectors in addition to the
CIS system, so I was way past the fuel problems.  The fuel issue is EASY, I
wouldn't say the air flow discussion is officially over.

Anyone have acess to a flow bench??

Javad

In a message dated 5/8/2002 10:20:07 PM Pacific Daylight Time,
bbell at surview.com writes:


> 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
>