Building a Flow bench, was: Measuring air flow

[Bernd Felsche]

ECMnut at aol.com tapped away at the keyboard with:

> I gave this some thought also.  
> Maybe a stolen blender motor?
> Wouldn't you also need to 
> setup an oil pump for the turbo?

If you're looking at comparable flow rates, you need a powerful
motor and a comparably-efficient means of moving air. Back in 1979,
I built a flow rig that used a large Rootes blower off a Nissan
truck, driven by a 10hp electric motor. A 200-litre drum was used as
a (tunable) flow damper.

A fractional-hp motor probably isn't going to do the job of
providing both the volume of air and the required pressure.
Remember; it's mass air flow in which you're interested. Calculate
the power required to accelerate a stationary air mass to the
required velocity through the meter.  If downstream of the meter is
near-atmospheric, power requirements will still be moderate.

I worked out that the inlet noise damper in my car required at least
300W to operate at maximum (rated) engine power, without taking into
account flow inefficiencies. That's why the thing has been sitting
on the shelf for the past 7 years.

Consider the pumping losses in your average engine. Although you
won't have to suck air through tiny valve openings and (perhaps
badly-tuned) inlets, there's quite a bit of power lost in breathing.

Consider also the power that your average turbo consumes to give you
one atmosphere of boost.

-- 
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