[Supras] AFM (hot wire type)

[berniek at technicaldevelop.com]

Roberto:

    The hot wire meter is not used on MkIII Supras but is used by 
others, primarily Nissan and GM although there are adaptations of the GM 
type for Supras (Rockey Fox is installing one).  To a large extent, they 
are (were?) self cleaning.  I had an '84 300ZX bought new which had 
one.  Every time you shut the engine off, it energized the wire to red 
heat for two seconds  to burn off any contamination.  We have a last 
generation Maxima which has one, and I do understand that they can be 
troublesome, although the one in my ZX was not.  They work by putting 
enough power into the wire to keep it at the same electrical resistance 
despite cooling from airflow, and the measure of airflow is how much 
power is put in.  There is also a fixed power variant in industrial 
applications, but I do not believe it is used in automotive work.  
Technically it is call a "hot wire anemometer". 


    If the wire is dirty, airflow will read low.  There are procedures 
for cleaning the wire with denatured alcohol, which should not be 
detrimental.  I've seen a product like or identical to the one you 
referred to.  It should be OK to use.  The wire is made of high 
temperature corrosion resistant alloy, perhaps nichrome.  I would not be 
afraid to do it, but would do the cleaning with care.


       BernieK