Re: alfa-digest V7 #868 - Quadriflow Air Filter

[Scott Fisher <sefisher@domain.elided>]

AlfaNeely@domain.elided wrote:
> 
>         The advantage is that the Quadriflow makes more noise than the stock
> air cleaner.  The disadvantage is that it is not ducted to the front of the
> vehicle and thus draws more warm air than the stock filter.

That was one concern...

>         Why not just take off the front of the Spica air cleaner box?  Inside
> are the ram tubes you want 

Are they?  As I said, this weekend is tape-measure time; I haven't
popped the Spica filter unit yet.  This is all pre-research.

Another thought was to get a used Spica box and enlarge the inlet duct
at the front, then run a larger tube to the radiator bulkhead.  I still
have some of the extra duct material left over from my '67 Lotus
Cortina, which did something like this; it's about 6" across, compared
to what looks like about 2" on the Alfa.  The stock 1558cc Lotus engine
was rated at 115 bhp, about what a stock U.S. 2-liter puts out.  True,
the Lotus uses 40DCOEs and a matched-length tubular header, but then
again the Alfa GTAs still beat 'em three years running. :-)

> and with the front of the box off, the induction
> noise is quite satisfying, in my opinion.

Reminds me: that's another point in favor of losing the engine-driven
fan -- the Alfa shouldn't, IMNSGDHO, sound like a turboprop.  

> If it sounds better, it has to be making more horsepower, right?  

Been there, done that, put the stock pieces back (on my '67).  The '67
will get its additional power the hard (but correct) way --
higher-lift/duration cams, multi-angle valve job, bullet-nose the
guides, clean up the ports, increase the compression slightly, and do
whatever's necessary to make sure the bottom end will hold together
(oooooh, threaded oilway plugs!).  Then change the jetting in the
40DCOEs to account for the new airflow characteristics, and use a
matched-length tubular header, preferably with the length/volume set to
optimize for 4000 RPM or below.  (The 1300 has *no* trouble making power
over 5000 RPM, thankyouverymuch...)

> Plus the opening is toward the source of cold air.

And that was part of my proposed "right" solution -- assuming that the
Q-flow ram tubes are a good length (well, they are for SOME range of
RPM, the question is whether that's a range that I use and that can
benefit from the resonant supercharging effect), said "right" solution
is to duct cold air to them; if that air could be from a high-pressure
spot outside the engine compartment, and enclosed in a box so that the
pressure would be retained around the inlets to the throttles, so much
the better.  And the more I thought about that, the more I thought it
sounded like the stock Spica setup...  which leaves only the question of
ram-tube length.

Next question: assuming that I *do* somehow manage to get more and
cooler air into the engine (we'll ignore the issue of getting those
nasty spent gases out for a moment), what do I do to the Spica unit to
compensate?  On SU carbs, I'd tweak the mixture adjusting nut a couple
of flats downward, test-drive the car, and do a plug-cut to see if I was
too rich and keep tweaking until it was just right.  What I'd like best,
of course, is a big red knob on the Spica pump saying TURN CLOCKWISE FOR
MORE POWER (even if it's printed in Italian), but I suspect there's no
such thing...

Thanks,

- --Scott

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