Building a Flow bench, was: Measuring air flow

[Eric Aos]

Take a look here for two how-to's on flowbenches.
http://www.spiritone.com/~eoa/Cars/Flow_Bench/Flow_Bench.htm

The furnace blower fan doesn't have enough vacuum (I tried one once). Get
the fans from http://www.grainger.com/ , you can order the same ones that
are used in a shop vac.

I've been thinking of a couple of MAP sensors and a PIC to calculate the
airflow across an orifice.

Eric Aos

> I'm not sure he's looking for WOT calibration, instead
> relying on the finer
> accuracy of the area most of us drive in.  However, this puts
> another piece
> into a puzzle for me:  I'd like to build a flow bench but
> I've never seen
> one in the flesh.  I had it all figured out except for two
> things - the fans
> and the flow measuring device.  The flow measuring device
> could be as simple
> as a known orifice and a manometer, but a discarded AFM might
> work too.
> Assuming these can flow 200 or 250 hp worth of air, that will
> be TONS more
> than I plan on measuring through each intake/exhaust port.
>
> I've got two residential furnace fans with motors kicking
> around - I don't
> know how much air they flow or how much water column they'll
> produce, but my
> 3 month old furnace filter gets pretty handily sucked against
> the side of
> the housing...  Aftermarket standard to flow bench testing is
> 28" h20, or 1
> psi.  Manufacturer's is 25", and lots of smaller shops use
> 10".  There are
> charts to compare flow rates from 10" to 28" depressions, but
> since I'll be
> looking at a similar port over and over again, what it
> ACTUALLY flows by
> aftermarket standards is of little importance to me, so long
> as it flows
> better than it did.
>
> The bench will be designed for vacuum, not pressure, and I
> guess that's okay
> with some creative mounting and measuring tactics.  There is
> a commercially
> available measuring device that uses a shop-vac as it's
> vacuum source, and
> it measures the observed airflow versus the observed depression and
> calculates the airflow at 28" - it's $600 USD.  One day at
> the porter's
> table might cost that much.  If anyone has any suggestions,
> I'd love to hear
> them.  Also, Bruce mentioned that the values for LT MAF
> sensor were in the
> archives - the only archives I can find are the monthly
> discussions and I'm
> loathe to look through THERE.  Anyone have somewhere they can
> point me?
>
> Thanks.
> Matt
>

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