Tire pressure gauge for ALFA's and ALFA compression readings

["Mike Nakamura" <mike_nakamura@domain.elided>]

While this may apply to other cars, it is intended to be used for ALFA's
only.
 
The sliding stick gauges use a metal spring for force against air
pressure let into one end. 
It's not measuring relative pressure between inside and outside of
Pirelli tires. The spring and sliding stick are attempting to measure
"true" pressure.

See: http://www.howstuffworks.com/pressure-gauge2.htm 


See:
http://www.trucktires.com/library/publications/periodicals/RealAnswers/9
9V4Issue3/ra8.htm 

The bourdon tube is a mechanical device, think of it as a tubular spring
(open on one end, the pressure goes inside). Getagauge.com claims the
bourdon tube gauges are not affected by altitude. The site says (or
implies) that altitude may affect a piston-type gauge.
See: http://www.getagauge.com/faq.cfm#accuracy 

Because both of these gauges use mechanical means to resist the air
pressure let into one end of the gauge, low ambient pressure should have
very little (no practical) impact at 14,000 feet above sea level. 

But this started with a query about ALFA compression a week or so ago,
then went to your reading at 14,000 feet above sea level compared to
compression reading at sea level. I still contend that you'll get a
lower reading at altitude. If you do a compression check at sea level
and have a series of batteries connected to a charger and to the car (to
maintain voltage and amperage) and you crank & crank, you eventually
reach a limit where the reading is "maxed out." Obviously you don't
introduce other variables. Yes the cables will warm, the starter will
get hot and slow, but ignore that for now. There is a "high" reading for
a particular cylinder given a set of circumstances.

Take the same circumstances and cylinder to 14,000 feet above sea level,
do it again; your "maxed out" reading will be lower. 

This may not apply in the Dolomites, but I pretty sure it works on Mt.
Fuji. Oh wait, the Dolomites (about 11,500 feet is tallest peak) are not
up to 14,000 feet and Mt. Fuji is only 12,388 feet high. Guess we'll
have to a tailgate a Ducati with a SUV in bumper to bumper traffic to
the U.S. Rocky Mts. while driving 50 mph in the left lane, wipers off,
dish soap on in order to go to the snow driving school to test our
Dunlop's.

Okay, I'm tired of this; at least I'll quit this thread now. 

Mike Nakamura
Fall City WA USA
mike_nakamura@domain.elided
91 Spider Veloce
94 164 LS
02 Dakota
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