Re: "As The Lug Nut Turns"

[Joe Elliott <jee@domain.elided>]

At 10:37 PM -0400 9/9/01, alfa-digest wrote:
>Date: Sun, 09 Sep 2001 21:02:33 -0400
>From: Bruce Murray <bmurray@domain.elided>
>Subject: Re: "As The Lug Nut Turns"
>
> >Joe Elliott <jee@domain.elided> writes
> >
> >
> >While I fear that I may sound like a stooge, I'm going to take this
> >opportunity to ask people to call heated-wire type airflow meters
> >"heated-wire type airflow meters."  I'm of the opinion that the term "mass
> >airflow sensor" doesn't exist and was made up by the same breed of idiot
> >that works behind the counter at AutoZone.  The term simply does not make
> >sense!  Perhaps "air mass sensor" would be appropriate since, between
> >volume and temperature, that's what an AFM tries to measure, but since
> >there's nothing mass(ive) about the airflow, the term "mass airflow sensor"
> >is entirely nonsensical.  Perhaps that would be an appropriate name for a
> >component on a jet engine, but I'd have nothing to do with an airplane that
> >had anything to do with L-Jetronic or goonies from AutoZone...
> >Anyway, can we agree not to call a heated-wire type airflow meter (or a
> >flap-type airflow meter for that matter) a mass airflow sensor, mass air
> >sensor, or MAS ever again?  If you must, I suppose I could live air mass
> >meter or air mass sensor, but since the real word is Airflow Meter can we
> >stick with that?  I realize this rant makes about as much sense as
> >insisting that Spider be spelled with an "i," but I thought I'd give it a
> >go anyway.
> >
> >Joe Elliott
> >(did I mention that I'm a double-major in mechanical engineering 
>AND English?)
>
>Well I am sorry, but I think Joe is wrong and I for one will continue to
>call is a mass flow sensor.  The heated wire airflow meter DOES measure the
>mass of the airflow passing into the engine. In the ones I am familiar
>with, the hot wire runs at a nominally constant temperature.  The current
>is passed through the wire at a sufficient rate to maintain a constant
>temperature at all air mass flow rates.  As the mass flow (volume X
>density) changes, so does the heat extracted from the wire. A control
>system senses the change of wire temperature and adjusts the current to
>bring the temperature back to nominal.  The amount of current passing
>though the wire is thus a direct indication of the mass flow entering the
>engine.  It is very clever because it gives a linear output with mass flow.
>
>A flap type sensor is not a mass flow sensor but is effectively a dynamic
>head sensor (one half rho vee squared).  A separate temperature sensor is
>needed to establish the value of rho and hence the mass flow.  The flap
>sensor output is non linear with flow and thus it is more complex to deal
>with its output in the ECU.  It is however more rugged which is why it was
>used until they developed ruggedized hot wire meters.

I realize I was going out on a limb with that one, but here's my 
defense--Bruce refers to a "mass flow sensor," which is not actually 
what I objected to.  "Mass flow sensor" or "mass/flow sensor" or even 
"air mass/flow sensor" would be entirely appropriate.  My objection 
was to "mass air sensor" which still makes no sense.  Bruce makes a 
good point though, about the heated wire type AFM giving linear 
output of mass flow, while the flap-type AFM provides separate output 
of temperature and flow.  But I'm still going to ask that since they 
both serve the same purpose that we call them the same thing.  If 
Bruce can convince the whole world to start saying "mass flow 
sensor," I'd be perfectly satisfied.  But the term that's already 
been standardized is "airflow meter."  "Mass air sensor" still makes 
no sense in the context of the English language, so I'm not going to 
use it.  But then I'm the guy that always says "manual gearbox," 
never abbreviating it to one word, as it gives me the creeps to use 
an adjective ("manual") as a noun.  And I say "gearbox" instead of 
"transmission" for similar reasons...

To inject some Alfa content...has anyone every built a forced-induction boxer?

Joe Elliott

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