REFLECTOR:TUNE, STRAIGHT EXHAUST PIPES
Brian Michalk
reflector@tvbf.org
Thu, 5 Feb 2004 10:22:26 -0600
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Hmmm, 12 inch tuned pipes?
>From your description of a flange, I'm assuming they bolt directly to the
cylinders? I wouldn't attach them to anything either. Safety cable is a
good idea.
Tuned to what? High RPM engines are much better suited to exhaust tuning,
and what it does is change the torque peak (mostly). There are scavenging
benefits involved, but a per-cylinder tube would have to be a bit longer to
take advantage of scavenging. It's quite a science and art to make a well
constructed scavenging exhaust system. Something I wish I understood
better, because (from what I've read) the theory doesn't always apply in
practice. You do your math to get in the ballpark, but the real world
engine doesn't match your mathematical model.
For us in the GA world where there are many combinations of compression
ratios, camshaft timings, intake manifolds/carb/injectors and cylinder
geometry even within the same engine line such as an IO360, a one size fits
all tuned exhaust system doesn't perform very well. It's a lot easier to do
on a stock 350 Chevy (or whatever) because they are all alike, so it pays
for someone to research the tuned system for that particular engine.
Generally, a shorter tube gives more torque at a higher RPM.
A longer tube give more torque at a lower RPM.
After having gone through my own engineering mating a turbo to a Franklin
(which still may not work), I might do it differently given a different set
of assumptions that running high power ops is only for takeoff and
emergencies. Everything else is below 85% power or some number. If this
were the case, I'd install high compression pistons with a good scavenging
cam, electronic fuel injection/ignition with a reliable knock detector
(ionic sensing). I would have either a spare tank of toluene, or water. In
the presence of knock, either inject water or toluene -- both increasing the
octane rating of the fuel.
The cool thing is that most of this is well within the normal homebuilders
grasp. The MSAVR is an open source/hardware engine control system, soon to
have ionic sensing. By the way, ionic sensing is a method of measuring
cylinder pressures using the spark plug as the sensor. Lot's of patents on
ionic sensing, and most of it is being developed from that technology. You
have to build it yourself, but the soldering is not difficult.
-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On Behalf
Of Tom Martino
Sent: Thursday, February 05, 2004 9:33 AM
To: reflector@www.tvbf.org
Subject: REFLECTOR:TUNE, STRAIGHT EXHAUST PIPES
I ordered and received six straight, 12-inch, tuned exhaust pipes –
stainless, with a generous flange and a reinforced collar. I have talked to
a few structural welders for ideas of brackets to tie them to the engine.
Each one of them examined the installation and told me they wouldn’t do
anything. They said I should just let them hang (with the exception of a
safety cable on each, in case they broke away.
Their reasoning is this: The exhaust tubes become part of the engine.
They will move and vibrate with the engine and a 12” extension does not hang
down far enough to create a mechanical “disadvantage”. They say if I tie
them to the engine, I could actually create a weak spot, causing it to
stress at that point.
I am not a welder, nor have I had personal experience with straight pipes
hanging 12 inches off of an engine. Can I get some feedback?
I plan on using a safety cable but should I go further?
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<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>Hmmm,=20
12 inch tuned pipes?</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>From=20
your description of a flange, I'm assuming they bolt directly to the=20
cylinders? I wouldn't attach them to anything either. Safety =
cable=20
is a good idea.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN=20
class=3D420505915-05022004></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>Tuned=20
to what? High RPM engines are much better suited to exhaust =
tuning, and=20
what it does is change the torque peak (mostly). There are =
scavenging=20
benefits involved, but a per-cylinder tube would have to be a bit longer =
to take=20
advantage of scavenging. It's quite a science and art to make a =
well=20
constructed scavenging exhaust system. Something I wish I =
understood=20
better, because (from what I've read) the theory doesn't always apply in =
practice. You do your math to get in the ballpark, but the real =
world=20
engine doesn't match your mathematical model.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN=20
class=3D420505915-05022004></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>For us=20
in the GA world where there are many combinations of compression ratios, =
camshaft timings, intake manifolds/carb/injectors and cylinder geometry =
even=20
within the same engine line such as an IO360, a one size fits all tuned =
exhaust=20
system doesn't perform very well. It's a lot easier to do on a =
stock 350=20
Chevy (or whatever) because they are all alike, so it pays for someone =
to=20
research the tuned system for that particular =
engine.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN=20
class=3D420505915-05022004></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN=20
class=3D420505915-05022004>Generally, a shorter tube gives more torque =
at a higher=20
RPM.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>A=20
longer tube give more torque at a lower RPM.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN=20
class=3D420505915-05022004></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>After=20
having gone through my own engineering mating a turbo to a Franklin =
(which still=20
may not work), I might do it differently given a different set of =
assumptions=20
that running high power ops is only for takeoff and =
emergencies. =20
Everything else is below 85% power or some number. If this were =
the case,=20
I'd install high compression pistons with a good scavenging cam, =
electronic fuel=20
injection/ignition with a reliable knock detector (ionic sensing). =
I would=20
have either a spare tank of toluene, or water. In the presence of =
knock,=20
either inject water or toluene -- both increasing the octane rating of =
the=20
fuel.</SPAN></FONT></DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN=20
class=3D420505915-05022004></SPAN></FONT> </DIV>
<DIV><FONT color=3D#0000ff face=3DArial size=3D2><SPAN =
class=3D420505915-05022004>The=20
cool thing is that most of this is well within the normal homebuilders=20
grasp. The MSAVR is an open source/hardware engine control system, =
soon to=20
have ionic sensing. By the way, ionic sensing is a method of =
measuring=20
cylinder pressures using the spark plug as the sensor. Lot's of =
patents on=20
ionic sensing, and most of it is being developed from that =
technology. You=20
have to build it yourself, but the soldering is not=20
difficult.</SPAN></FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px">
<DIV align=3Dleft class=3DOutlookMessageHeader dir=3Dltr><FONT =
face=3DTahoma=20
size=3D2>-----Original Message-----<BR><B>From:</B> =
reflector-admin@tvbf.org=20
[mailto:reflector-admin@tvbf.org]<B>On Behalf Of </B>Tom=20
Martino<BR><B>Sent:</B> Thursday, February 05, 2004 9:33 =
AM<BR><B>To:</B>=20
reflector@www.tvbf.org<BR><B>Subject:</B> REFLECTOR:TUNE, STRAIGHT =
EXHAUST=20
PIPES<BR><BR></DIV></FONT>
<DIV class=3DSection1>
<P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
style=3D"FONT-FAMILY: Arial; FONT-SIZE: 10pt">I ordered and received =
six=20
straight, 12-inch, tuned exhaust pipes – stainless, with a =
generous flange and=20
a reinforced collar. <SPAN style=3D"mso-spacerun: yes"> </SPAN>I =
have=20
talked to a few structural welders for ideas of brackets to tie them =
to the=20
engine. <SPAN style=3D"mso-spacerun: yes"> </SPAN>Each one of =
them examined=20
the installation and told me they wouldn’t do anything. <SPAN=20
style=3D"mso-spacerun: yes"> </SPAN>They said I should just let =
them hang=20
(with the exception of a safety cable on each, in case they broke=20
away.<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
style=3D"FONT-FAMILY: Arial; FONT-SIZE: =
10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
style=3D"FONT-FAMILY: Arial; FONT-SIZE: 10pt">Their reasoning is =
this:<SPAN=20
style=3D"mso-spacerun: yes"> </SPAN>The exhaust tubes become =
part of the=20
engine.<SPAN style=3D"mso-spacerun: yes"> </SPAN>They will move =
and=20
vibrate with the engine and a 12” extension does not hang down =
far enough to=20
create a mechanical “disadvantage”.<SPAN =
style=3D"mso-spacerun: yes"> =20
</SPAN>They say if I tie them to the engine, I could actually create a =
weak=20
spot, causing it to stress at that point.<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
style=3D"FONT-FAMILY: Arial; FONT-SIZE: =
10pt"><o:p> </o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial size=3D2><SPAN=20
style=3D"FONT-FAMILY: Arial; FONT-SIZE: 10pt">I am not a welder, nor =
have I had=20
personal experience with straight pipes hanging 12 inches off of an=20
engine.<SPAN style=3D"mso-spacerun: yes"> </SPAN>Can I get some =
feedback?=20
<o:p></o:p></SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3D"Times New Roman" size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; mso-no-proof: =
yes"> </SPAN><o:p></o:p></FONT></P>
<P class=3DMsoNormal><FONT face=3D"Times New Roman" size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt">I plan on using a safety cable but should I =
go=20
further?<o:p></o:p></SPAN></FONT></P></DIV></BLOCKQUOTE></BODY></HTML>
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