Douglas Fir wrote:

Paul

I noticed a lot of posts recently about tuning intakes.  I assume

the

same
is true for exhausts.  If the angled  outlet pipe of tangential
muffler
Jerry is making has the exhaust pipe sticking out in the slip

stream

I

believe it should exhibit a slight vacuum thereby helping to draw

out

the
exhaust better.  Turbo props exhausts take advantage (need to)

have

this
design.

Q. If this vacuum phenomenon is maximized does it alleviate the

need

for
tuned exhausts?

Seems hard to calculate the tuning on how gases travel in a large
chamber.

Doug in Japan

They are a big unknown. Hope to measure the pressure when I get my

dyno

going. Everett Hatch maintained the optimum length for two

individual

pipes
was 32 inches. Most of the headers that Racing Beat sells are

about

this
length. The speed of sound varies from the intake manifold due to

the

heat
of the exhaust gases.


Paul Lamar

Doug,  I expect low pressure at the exhaust pipe outlet to help
scavenge exhaust gasses.  How pronounced the effect will be is

unknown.

   Once the lower cowl is fitted, the pipe can be trimmed to enhance
this effect.    Jerry

Question for the group:  (Related question but a stretch...)

In some of the early Cessna 170 pictures ( w/ twin exhaust exiting out
of the bottom of the cowl roughly perpendicular to the fuselage), they
show the exhaust pipes cut so that the slant faces forward (Face into
the airstream).

Someone mentioned in an article that there is actually less backpressure
when the pipes are angled this way.  Likely makes little difference but
doesn't sound quite right.

Anyone care to comment?   Any use in this endeavor?

Steve Webre
Broussard, LA
'48 C-170

 
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