2/4 bbl FI intake

["Allan & Kathryn Weidenheimer" <allanw@domain.elided>]

I don't have any data, or a hard answer, but hey, I can kick out a theory--
Consider intake plenum volume.  I know I've read mention of this in
racing/hi-perf magazine articles.  As I recall, a larger intake plenum
volume
at a given RPM, results in less velocity of the intake air mass.  This
lower
velocity then means it takes longer fo a richer mixture, such as when 
accelerating, to get from the injector to the cylinder.  

One of the reasons that multi-port FI is so nice is the immediate response,
with the injectors just before the heads.  So when the computer calls for
more 
fuel (like when you "stomp on it"), it is at the cylinders almost
immediately.  
With throttle body injection, there is a certain volume of air/fuel in the
intake that 
must be drawn into the cylinders before the richer mixture reaches them. 
Also 
along that longer distance for the fuel/air mix to travel comes increased 
opportunity for the fuel to puddle in the intake when the velocity is low. 


With the low RPM nature of an IHC, it would be
my opinion that the 2 BBL intake with a 2 BBL throttle body would be
better.  In looking at my 4 BBL intake, it seems to have much more volume
than a 2 BBL.  I have a 2 BBL intake in the garage, I could measure the
total 
volume. Anyone have a 4 BBL intake 'laying around' that they could measure?
It would make for some interesting data.

With 670 CFM for a 2 BBL FI, I don't see where a 4 BBL
is even necessary.  Is the 2 BBL available with the digital/feedback
system?

I seem to recall that Holley calls for a 4 BBL intake, I assume
that is because they are basically using a GM injector body that has
that funky bolt pattern.  Is it any big deal to have the IHC manifold
tapped to mount the Holley unit?

Lastly, I would suggest that the bore sizes in the IHC 2 BBL intake should
be
matched to the Holley injector body, so as to have smooth airflow.

Just my rambling $.02
Allan Weidenheimer
72 1210 Pickup