I think your analysis of what the gulp valve does is essentially correct. I
had always thought that it operated in reverse ... that it sensed the fast
throttle closing and diverted the air from the air pump/rail to the air
filter, but it seems more likely, upon reflexion, to do what you suggest.
I'm often (WARNING: philosophical note here) bemused by our struggles to
understand our beasts and reminded, humbly, that though we think these
emissions systems 'kludgy' or 'onerous', they were in fact designed by
engineers, not shade-tree mechanics. In trying to mucker with them in any
way, I think it's useful first to think like an engineer, and consult
something outside of the usual Haynes manual for support. Auto industry
standard texts on emissions control systems come to mind. ::shudder::
This strikes me more and more as I work on ever-newer cars (my better half's
93 Dodge Spirit, for example), and my poor 1970's gearhead brain struggles to
decipher the meaning behind 'throttle position sensor', 'port pressure
maintenance valve', 'CO2 relief filter' and the like.
I try to approach anything I do to a car from a zen-like perspective (Zen and
the Art of LBC's? Hmmm....I see a book coming.) Strive for balance, and
treat the engine as a system rather than isolated parts. Touch the web here,
it resonates there ... that sort of rubbish. I think the example of the
restrictor on the crankcase ventilation tube is a good example of that.
Well, back to the shop to meditate on why the 93 Spirit hiccoughs at highway
speed. Cheers. :)
ckr
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