[Diy_efi] AIR fitting and A/C (off topic)

David Allen davida1
Sun Sep 11 07:06:12 UTC 2005


  The V5 compressor is a variable displacement, pressure-compensated unit.
It has a swashplate that moves and changes the stroke length the pistons
travel for each revolution of the compressor shaft.  It has a compensating
element that senses the low side pressure and varies the swashplate angle to
maintain 28 to 32 PSI evaporator pressure.  It works better, is quieter and
vibrates less than an R4.
  A fixed-displacement compressor must cycle on and off to maintain the
low-side pressure at 28 to 32 PSI (approx- varies w/ systems).   Instead of
cycling, a V5 will increase or decrease the compressors "size" to maintain
the appropriate low-side pressure.  If the heat load on the A/C is
increased, the stroke of the compressor increases to keep the pressure
constant.  If the engine RPM increases, the stroke decreases to keep the
pressure constant.
  Once the A/C is on, the compressor clutch never cycles.  It runs
continuously as long as the A/C is on; assuming the high-pressure safety
switch or the low-refrigerant safety switch don't shut it down. There is no
A/C surge and the clutch lasts for ever! The compressor uses only exactly
the amount of power the refrigeration cycle needs to cool the car.
  A V5 is a well-made unit.  It is all rollerbearing and has its own oil
reservior.  Unlike the R4 and DA6 it is not easily damaged by running low on
refrigerant.  (You know how the R4 units all rattle permanently after
running low on freon one time.)
  The bracket had to be adapted.  I had to add spacers, and a tail bracket
to support the back end of the compressor. It wasn't that bad. It's been so
long ago I can't remember the details! Actually I found a picture on my
website that shows a partial view of the bracket spacer and adapter (see
link below).  The same hoses worked.  The clutch pulley and magnet are the
same between most R4, HR6/ DA6, and V5 compressors. You can interchange them
to get the right combination of serpentine or vee belt, pulley diameter, and
connector style.  I like the smallest pulley available for these units
because it gives the highest compressor RPM at idle.  This A/C is just as
cold at idle as it is moving down the road.
  I know this is off-topic and complicated but a good A/C is very important
in the region where I live!!
  As for the AIR system on my engine? I used the original Nova manifolds and
they never had any AIR lines.  I have no AIR system nor catalyst.  It's a
1972 model car and on top of that Alabama is not an emissions state.  With
TBI, closed-loop AFR control using a 4-wire O2 sensor, and high compression;
this engine is many times cleaner than when the car was new.  Back then it
had a 2-barrel carb, points ignition and 7:1 compression.  Now, it uses half
the fuel it did when new. Lets just say I don't feel guilty removing the AIR
components from the engine.
  When performing a SMOG system removal on a friends early-80's Toronado, we
used brass plugs in the manifolds.  They were available at NAPA but I don't
remember the size.
David


http://home.hiwaay.net/~davida1/custom.htm

> >
> >   With the serpentine belt system, belt alignment can be a pain when
> > modifying.  After replacing the alternator with an oversize unit and
> > retrofitting a V5 variable displacement A/C compressor, it
> > took some playing
> > around to get the belt to run without chirping or running off
> > the waterpump
> > pulley!
>
> Why the new A/C?  fits better or works better?  It doesn't look like it
> would fit into the R4 bracket, did you get a new bracket for that side?
>
> --steve
>
>
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