Back flow?(don't tell me this belongs on a sewer!)

[talltom]

-----------------------------
> 
> From: RABBITT_Andrew at mv8.orbeng.com.au
> Date: Mon, 5 Aug 1996 08:02:16 est
> Subject: re: AFMs
> 
> >>Is it a MASS FLOW measurement?
> 
> NO, vortex shedding frequency is a function of flow velocity,
> therefore it's only volume flow metering.  The pressure and temp.
> sensors are only to do the corrections, which alledgedly leads to
> messy lookup tables and calculations in the OEM ECU. (yuk!)
> 
> >>Does a problem occur at low (read idle) flow rates (of resolution)?
> 
> I shouldn't think so, it should be just a matter of sizing the vortex
> shedder and minimum flow velocity appropriately. (my opinion only)
> 
> >>All this stems from me being a little nervous about using Bosch
> hotwires in a high vibration offroad application.
> 
> If you're worried about vibration on a hotwire, try using the bosch
> hot-film sensor (HFM-2) as fitted to many late model BMW's and
> probably many other European cars.  Take a look at the latest 540i
> (4.4L V8) which should be good for your application
> 
> Also, the Hitachi bypass meter fitted to most fords (EEC iv) is an
> analogue output, not frequency.
> 
> Also, for everyone's info, Bosch has recently started production on a
> hot-film meter capable of measuring back-flow (properly!)  A neat
> piece of design using micro-machined silicon technology.
> 
> Andrew Rabbitt
> Orbital Engine Company

Hang the hell on here! Are you saying what I think you're saying?
This thing can measure air flow in either direction, relatively
accurately? If this the case, did anybody else see all those 
arguments about wild cams up and fly out the window like I just did?