Rino Lacombe wrote:

I have a question about the throttle body for Tracy and others.
The information I have is the following:
The 2 primary intake runners are 1.25" dia.
The 2 secondary intake runners are 1.77" dia.,  I find a total area of
5.89 square  inches.

The throttle body has 3 (venturi) of 1.77" dia, I find a total area of
7.38 square inches.
The equivalent (venturi) would be 3.125" dia. for a total area of 7.38
square inches.
Question: Do I really need a throttle body that large? (3.125" dia.)
The pipes to and from the intercooler are only 2" dia.  Is there a
reason to have the throttle body
that much larger than the pipe (2") that feeds it?  -- The bigger the
heavier.
Would a 2.55" throttle body be large enough.
Thanks
Rino

Opinions vary widely on this but my answer is yes,  2.5" dia is plenty for a
13B developing 180 - 200 HP.  Note that the throttle body for the latest
RX7s making 285 HP is about the same as the early EFI 13Bs making only 146
HP.  I use only two of the 1.77" barrels from the stock (1988) version and
find that it is nicely matched to the engine making around 185 HP.

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

Just check your intake manifold pressure at wide open throttle and compare it
to atmospheric pressure on the other side of the throttle body.
This can be down with a cheap water manometer.

Paul Lamar
 
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