Hi Jos
Gilles was kind enough to put "my test information" on his site.
Your information is absolutely incorrect.
If you reach the auto-ignition temperature, that is the temperature that
the substance will auto ignite.
Your experience and subsequent conclusion that since fuel squirted in your
car and didn't ignite, thus that must be the worst case scenario, is not
in fact the case.
First off what was the percentage of power your motor was making and for
how long? I know if I drive my Volvo Turbo Wagon at 75MPH on flat ground
and if I pull right over the exhaust manifold is just barely glowing. If I
tote my balloon trailer and set manifold pressure to 29.92 inches, lets
say I am making 45% power, yikes if I pull over I can easily read from the
glow of the manifold that is way beyond red hot! If you take a 914 that is
tooting at 115% power for a minute, I am certain it is a lot hotter than
my 45% powered Volvo and I can say without hesitation if you spew fuel on
it it will auto ignite. My gut feeling is 65% power on a 914 is plenty to
heat turbo/manifold to auto-ignition.
As far as my preference for non aluminium fittings FWF, it is the same
preference as local DAR and IA aeroplane mechanics. They have seen plenty
of fittings fail. Remember that the fittings are the interface between a
stationary airframe and a wiggling motor. Fatigue cracking is a lot more
common than you may think according to their experience.
Yes a carb and other motor items are aluminium, but the stresses imposed
are often reasonable. In addition to fatigue cracking, aluminium will fail
far easier than steel if you stress. Give a try of an aluminium and also a
steel barb fitting stressed to failure and you will see what I mean.
Your motor can wiggle around an awful lot if prop gets out of balance, or
if fuel distribution is compromised or a cylinder fails to fire properly
for whatever reason, or if you put a trauma to your aeroplane.
Ron Parigoris
BTW I just went out with my Volvo Turbo Wagon, climbed up a 1/4 mile long
hill that is bout 200 feet high with about 34 inches MP, pulled over on a
side street, and poured a half a soda cap filled with fuel on the manifold
with motor off, instant ignition! My test on Gilles site was with 100LL,
this one was with 92 octane mogas.
|