Lynn
does such a great job at painting a very clear picture of the dynamics of an
internal combustion engine.. Thank you sir... As a side note those of us
using an engine in close to a steady state application are very
lucky because tuning the intake is alot easier then in a application that
has a wide powerband range. A coupleof sharp motor tuners and a day or so on
a good repeatable dyno can zero in on acceptable intake design that should
set a good baseline for what really works. You can sliderule / use fancy
computer programs and other methods of determining optimum designs but
nothing trumps real time data in a running engine. Just my .02 cents
worth.
Ben Haas
www.haaspowerair.com
To: flyrotary@lancaironline.net
Date: Wed, 31 Mar 2010 01:09:18
-0400
From: lehanover@gmail.com
Subject: [FlyRotary] Tuned
lengths?
A "tuned" intake covers a wide Varity of techniques ranging for
Hermholtz,
RAM, Dynamic Intake, Inertia, etc,. There are basically
three conceptually
different approaches although they tend to merge under
certain conditions.
You have the resonant tuning, the pulse tuning and
the inertia turning
concepts. However, truth be known all three
phenomena occur in most intake
systems - it's a matter of
emphasis.
The thing that really complicates it is the fact that
within any induction
or exhaust system you have Finite Amplitude Waves -
the power of these pulse
makes a 135 db sound wave very puny - these
pulses can actually pound metal
apart. They do not interact
linearly as do "sound waves" - in fact they can
respond in what at first
seems to be weird ways. For instance they may
reverse there
"polarity" depending on whether they encounter an open or
closed
termination.
It has only been with the advent of digital computers
has it been practical
to even try and model the effects of these waves in
an induction system. I
find them fascinating.
Here are a few
references that some of you might find interesting.
http://home.earthlink.net/~redcat/pulse_ram/theory.htmlhttp://www.motionsoftware.com/simtech.htmhttp://www.proracingsim.com/dynomationmainpage.htmhttp://www.audietech.com/DMfeaturetable.htmEd
Anderson
Side intake port engines produce different tuned effects than do
Periphery ported intake engines.
Side exhaust ported engines produce different tuned effects than do
periphery ported exhaust engines.
The most powerfull engine would be the Periphery intake and exhaust
ported engines.
Although the intake and exhaust open and close events are reported in
degrees of crankshaft rotation
just like a side port engine, the periphery ports never actually close.
So, tuned lengths produce bigger changes than in the side ported engine. So,
one end of the tune length is virtually open all of the time, and worse one
end is exposed to changeing pressures all of the time.
The overlap (Intake and exhaust open at the same time) is huge. So
exhaust back pressure can poison the intake quite badly.
In the side intake ported engine one end of the column is closed solid
by the side of the rotor. Intake and exhaust overlap may be minimal or
extensive. Column lengths produce crisp tuning. Overlap with peripheral
exhaust ports may have less effect. Exhaust back pressure can remove much
power.
Side intake and exhaust Renesis) may have no overlap at all. The center
exhaust ports share an exit that is too large right at the port face. Even
with no overlap, the intake can be poisoned by exhaust gasses being held in
the chamber by a poor exhaust system. Exhaust system has three
outlets
Possibly less sensitive to back pressure than other designs When
converted to a Periphery intake port, may still have low overlap.
Lynn E. Hanover.
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