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Allen.
First off they are pricey.
There are two types of stub stack available for the 1.5" SU. Cast and machi=
ned. I've not been impressed with the design of the cast ones which run abo=
ut $20 each. The machined ones look like they will do the job, but run abou=
t $32 each.
APT offers both types: http://www.aptfast.com/ListItems/SubCategory/SU%20Ca=
rburetors/Stub%20Stacks%20and%20Ram%20Pipes.aspx
Second.
At lower rpm the carburetor piston offers more flow blockage than poor flui=
d dynamics at the air filter plate. At WOT, it's a different matter.
There are no doubt all kinds of peaks and valleys in fluid flow during the =
dynamics of accelerating and cruising up to 3500 rpm. I was told by one of =
my engineering teachers that anyone who professes to be an expert on fluid =
flow is a liar. He stated that it is still more of an art than a science an=
d a dark art at that. In fact, after receiving a doctorate in the field he =
determined that aircraft are kept in the air by smoke and mirrors because t=
he dynamic forces at work are too complex to be understood by the likes of =
mankind.
If you have to run a pancake style filter, then by all means use a stub sta=
ck. Before they became available for the DCOE, I used to cut down the stand=
ard long trumpets and braze them up into short stacks. They will make some =
difference, though I doubt it's going to be really noticeable.
Just work on the basics first.
From: zmagnette-bounces@autox.team.net [mailto:zmagnette-bounces@autox.team=
.net] On Behalf Of Allen Bachelder
Sent: Friday, November 15, 2013 11:03 AM
To: List for the Z Magnette Group - North America
Subject: Re: [Zmagnette] Stub stacks
Kelvin - your point is well-taken. Are you saying that even if everything e=
lse is spot-on, it's still not worthwhile to mess with velocity stacks for =
those of us who spend most of our lives below 3500 rpm?
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</o:shapelayout></xml><![endif]--></head><body lang=3DEN-US link=3Dblue vli=
nk=3Dpurple><div class=3DWordSection1><p class=3DMsoNormal><span style=3D'f=
ont-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Allen. <o=
:p></o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:11.0pt;fo=
nt-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p=
><p class=3DMsoNormal><span style=3D'font-size:11.0pt;font-family:"Calibri"=
,"sans-serif";color:#1F497D'>First off they are pricey. <o:p></o:p></span><=
/p><p class=3DMsoNormal><span style=3D'font-size:11.0pt;font-family:"Calibr=
i","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=3DMsoNo=
rmal><span style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";col=
or:#1F497D'>There are two types of stub stack available for the 1.5” =
SU. Cast and machined. I’ve not been impressed with the design of the=
cast ones which run about $20 each. The machined ones look like they will =
do the job, but run about $32 each. <o:p></o:p></span></p><p class=3DMsoNor=
mal><span style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";colo=
r:#1F497D'>APT offers both types: <a href=3D"http://www.aptfast.com/ListIte=
ms/SubCategory/SU%20Carburetors/Stub%20Stacks%20and%20Ram%20Pipes.aspx">htt=
p://www.aptfast.com/ListItems/SubCategory/SU%20Carburetors/Stub%20Stacks%20=
and%20Ram%20Pipes.aspx</a><o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'=
><o:p> </o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:=
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Second. <o:p></o:p=
></span></p><p class=3DMsoNormal><span style=3D'font-size:11.0pt;font-famil=
y:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p clas=
s=3DMsoNormal><span style=3D'font-size:11.0pt;font-family:"Calibri","sans-s=
erif";color:#1F497D'>At lower rpm the carburetor piston offers more flow bl=
ockage than poor fluid dynamics at the air filter plate. At WOT, it’s=
a different matter. <o:p></o:p></span></p><p class=3DMsoNormal><span style=
=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p=
> </o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:11.0p=
t;font-family:"Calibri","sans-serif";color:#1F497D'>There are no doubt all =
kinds of peaks and valleys in fluid flow during the dynamics of acceleratin=
g and cruising up to 3500 rpm. I was told by one of my engineering teachers=
that anyone who professes to be an expert on fluid flow is a liar. He stat=
ed that it is still more of an art than a science and a dark art at that. I=
n fact, after receiving a doctorate in the field he determined that aircraf=
t are kept in the air by smoke and mirrors because the dynamic forces at wo=
rk are too complex to be understood by the likes of mankind. <o:p></o:p></s=
pan></p><p class=3DMsoNormal><span style=3D'font-size:11.0pt;font-family:"C=
alibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=3D=
MsoNormal><span style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif=
";color:#1F497D'>If you have to run a pancake style filter, then by all mea=
ns use a stub stack. Before they became available for the DCOE, I used to c=
ut down the standard long trumpets and braze them up into short stacks. The=
y will make some difference, though I doubt it’s going to be really n=
oticeable. <o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'=
font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p>&nb=
sp;</o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:11.0pt;fo=
nt-family:"Calibri","sans-serif";color:#1F497D'>Just work on the basics fir=
st. <o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'font-size:11.=
0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></sp=
an></p><p class=3DMsoNormal><span style=3D'font-size:11.0pt;font-family:"Ca=
libri","sans-serif";color:#1F497D'> <o:p></o:p></span></p><p class=3DMsoNor=
mal><span style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";colo=
r:#1F497D'><o:p> </o:p></span></p><p class=3DMsoNormal><span style=3D'=
font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p>&nb=
sp;</o:p></span></p><div><div style=3D'border:none;border-top:solid #B5C4DF=
1.0pt;padding:3.0pt 0in 0in 0in'><p class=3DMsoNormal><b><span style=3D'fo=
nt-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span sty=
le=3D'font-size:10.0pt;font-family:"Tahoma","sans-serif"'> zmagnette-bounce=
s@autox.team.net [mailto:zmagnette-bounces@autox.team.net] <b>On Behalf Of =
</b>Allen Bachelder<br><b>Sent:</b> Friday, November 15, 2013 11:03 AM<br><=
b>To:</b> List for the Z Magnette Group - North America<br><b>Subject:</b> =
Re: [Zmagnette] Stub stacks<o:p></o:p></span></p></div></div><p class=3DMso=
Normal><o:p> </o:p></p><div><p class=3DMsoNormal><o:p> </o:p></p>=
</div><div><p class=3DMsoNormal>Kelvin - your point is well-taken. Are you =
saying that even if everything else is spot-on, it's still not worthwhile t=
o mess with velocity stacks for those of us who spend most of our lives bel=
ow 3500 rpm?<o:p></o:p></p><p class=3DMsoNormal><o:p> </o:p></p></div>=
</div></body></html>=
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