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Tracy
Thanks for that info.
I have been trying to get my mind around how to establish the best vacuum
signal around idle, and like you said it's a pretty small signal.
The flat ground needles seem to have overcome this
with their design as they claim that the flat side ( rear) of the needle creates
a vacuum sufficient to lift fuel 6" to 8" with 1 PSI fuel pressure - which
I found difficult to comprehend. These carbs have the so called 'perfect inlet
shape', I assume by this they mean no venturi ( choke) or butterfly
restrictions.
What also amazes me is that in all the Internet
carb calculators provide answers in CFM, yet these carb manufacturers rarely
give that type of flow information, especially Edelbrock and Aero Carb - I
wonder why?
Revmaster didn't have it readily to hand but did go
to the trouble to find out. It all seems very strange to me!!
Further investigation required!!
George ( down under)
I think this is the spec on ventury vacuum (V V) at max specified
CFM. Performance carbs (generally 4 barrels) are designed with about 1/2
the ventury drop as "grocery getter" carb designs. The less the V V, the
better WOT performance (more MAP) but the harder it is to design due to
the smaller signal. 10" H2O is a pretty small signal for MAX CFM.
BTW, This is unrelated to throat size.
Tracy Crook
On 8/23/07, George
Lendich <lendich@optusnet.com.au>
wrote:
Ed, Lynn, Bill or anyone.
I'm trying to figure out how to extrapolate
various air flow figures which have different vacuum testing parameters such
as those with 10" of water verses those with 12" of water and 20.4" of
water. I don't know where the 20.4" of water comes from, but apparently it
does exist.
I assume there is some calculation which can be
applied?
I'm only concerned with extrapolating from one
( known value like 10") to another ( like 12") - for comparison
purposes.
George ( down
under)
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