Hi Paul,

Is the volume of the  plenum chamber on a throttle body/plenum setup
critical in any way  ?

Cheers Chris in  NZ

It has something to do with it. Technically it is called  a
Helmholtz resonator.


Paul  Lamar



Hi Paul,
Thanks for all  that, very helpful, I don't know
what I'd do without all this help  and
info from your newsletter, I might have been reduced  to
(dare I say it) putting in a
piston engine  !
Cheers Chris in  NZ.



Chris,
This explains it pretty  well.
Paul Lennemann

Hi!:  attached please find a chart about the different results
of different ducts  and openings, that would
apply also to  Wankel RCEs' Ports, it's taken from the 2005
edition of the 'BOSCH -Manual  of Automobile Technologies',
so, it's possible  that a bigger version exists, sorry, legends
are in Spanish, but Google  translate is quite
good in changing Spanish  into English, with just a copy and paste
of text.

Regards.  Salut


Jose Gros-Aymerich
Madrid,  Spain





The current thinking in V-8s is big volume plenums with  smaller diameter
runners.
The Daytona prototypes use two length runners with the engine  split into
two 4 cylinder engines, so as to spread out the torque peak. The  power is
then limited by the sanctioning organization with rev limits. Large
 plenums
make for broader torque bands.
Smaller plenums make more peak HP and are more sensitive to  runner length
and diameter.
Large displacement engines generally are insensitive to small  changes in
tuned lengths and runner diameters.
Small displacement engines (Rotaries) can become downright  snotty when it
comes to tuned length and runner diameter. Changing 1/8" spacer  in the
intake can be a visible change in output. The Renesis with no overlap did
 away
with most of that problem.
Notice the smooth long small diameter (High velocity) runners  in the
complex Renesis intake system.

Less is more when porting. The odd shape of the side intake  port has you
close to TOO MUCH area before you start. Thus the single  Periphery port
can
have an advantage in simplicity, and velocity.

Bernoulli:
http://mitchellscience.com/**bernoulli_principle_animation<http://mitchellscience.com/bernoulli_principle_animation

High velocity porting of motorcycle engines.

http://www.mototuneusa.com/**think_fast.htm<http://www.mototuneusa.com/think_fast.htm

Runners need to end in a trumpet bell shape. Better if no  obstruction
within one bell diameter of the runner centerline. The runner may continue
inside the plenum to achieve a preferred tuning length. The bell end
 shape then
becomes even more important.

Lynn E. Hanover

That is cars where a wide torque band is needed.
We don't need wide torque bands in aircraft engines.
Prop load is the square of engine RPM.
Set the torque peak to cruise RPM.

Large ports and runners are called for to keep the
air speed in the runners down. Skin friction drag
in the runners is proportional to air speed squared.
Just like the outside of an airplane.

This is why P-ports with 2 inch dia. runners result in 25%
more power and a lower fuel burn per HP generated..


Paul Lamar



Hello Lynn,

Is Motoman still issuing his news letter?
It looks to me that he has given up.

Rolf


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