Also note that Tracy flies with 2/3 of the stock TB and as far as I know
he has never reported a problem with restricted airflow. I'm pretty sure he
flies with an MP gauge. Not saying it would be a problem to have a larger
TB but apparently there is no penalty for the smaller one like Tracy's on
an NA engine.

Mike Wills

I would not say that. Perhaps Tracy can get some more power. As far
as I know he has never measured the pressure drop across his throttle body.
What ever the MP gage says it might be higher on the other side.
Note the Leman engine had individual slide throttles for each intake
pipe and rotor that are completely out of the way at WOT.

Chuck Dunlap, as I recall has some before and after data but he may have
a large restriction some place else in the system that will mitigate
the effect of a larger TB. Both Perry Mick and George Graham noticed
a HP loss with air filters. I think Perry has some numbers on MP.

Paul Lamar

Yes, I had over 2" of manifold pressure loss.  It was because
I didn't leave enough clearance around the stock rx-7 airfilter
in a custom box I made.  So most of the air was going through
about 1/4 of the filter.  I flew only the first 10 hours that way
before I discovered it.  Have been flying with no air filter ever
since, 220 more hours now.  The assumption is I'm only operating
off hard surface runways so should be low dust level.

I'm using the stock 3-barrel TB.

--
Perry Mick
Duckt N7XR
http://www.ductedfan.com

I might add that Perry is not near max HP or max airflow  because his 
direct drive ducted  fan tip speeds are near super sonic at 5500 RPM.

Paul Lamar
 
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