>The air pump feeds air through the check valve then through a
>single pipe (which is now copper on mine), to the base of the exhaust
>manifold. There is no visible diverter valve so I am not sure how that
>could be the problem.
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>From what I read on the subject a while back (not specific to Spitfires)
but when used this way (no gulp, anti-afterburn, diverter valve, or
whatever the manufacturer calls it), the calculated back pressure in the
exhaust system is what does the metering (and one reason that many smog
requirements don't allow ANY changes to the exhaust system). Very simply
put, the system is designed with a certain back pressure. During times of
negative pressure in the exhaust, air is drawn through the check valve,
from the air pump through the air rail system, into the exhaust manifold at
a specifically located inlet, and during positive pressure cycles it is
prevented from entering via the check valve which only allows flow one way
(the pressure in the exhaust manifold is higher than the pressure of the
air pump). In effect doing almost the same thing as the diverter valve, but
not as efficiently (from the standpoint of engine efficiency). It
certainly would be cheaper to mfg and maintain, but most certainly is not
the optimum condition for maximum power - This would also be one reason
besides the obvious (but rather small) power requirement of running the air
pump itself, that when you remove this particular equipment, and stick on a
less restrictive muffler you notice a power increase - Everything smog
related that was "added on" after the fact so-to-speak, is usually
inter-related, and changing one item can often times have disastrous
effects on everything else. If you know how the system is suppose to work,
then you have a much better chance of modifying the equipment without
affecting the operation of rest of the system-if that is your desire. I am
not advocating modifying anything, just showing what the results can be of
just arbitrarily removing and plugging things up.
Solving the original problem. . .well. . .that's the kicker isn't it.
Possibly the check valve may be bad among other things. If anything in the
system was changed from stock operating parameters, your back to square one-
Barry Schwartz (San Diego) bschwart@pacbell.net
72 FI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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