Twin Centrifugals VS Single
BamaInstrument
BamaInstrument at email.msn.com
Tue Apr 17 21:37:59 GMT 2001
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I like the concept and have been looking at something similar. It seems =
that a large centrifugal supercharger would work okay, but I don't like =
the pressure/flow (and thus) torque curve. The results from a =
centrifugal unit are something like the square of the tip speed. If the =
diameter of the charger is larger then the tip speed can be accomplished =
with a lower RPM. I've been looking at gearing directly to the crank, =
as opposed to belt drive. The cam is a VERY high and variable load to =
the crank and seems to be handled quite well
I like the concept of some type of variable gearing. The early Paxtons =
(?) did this by changing the driven pulley diameter. Mainly I'd like to =
have a much broader torque range than would be available with the =
current engine centrifugal super chargers.
dh
----- Original Message -----=20
From: Walter Sherwin=20
To: gmecm at diy-efi.org ; diy_efi at diy-efi.org=20
Sent: Friday, April 13, 2001 12:25 AM
Subject: Twin Centrifugals VS Single
Forwarded from another list.....
>Here's something I've been tossing around in my mind, for street toy =
use, and I'd love to hear more from the group........
>Let's say you have a large displacement stroker motor, and you desire =
to artificially stuff it's hunger with centrifugal supercharging (non =
manufacturer specific at this >point). The typical approach today would =
be to seek out a largish single centrifugal unit that would do the dirty =
job, and pulley it to gain the max desired air flow/boost at >a specific =
engine speed. This would net you a large diameter centrifugal, =
operating at a somewhat less than maximum impeller speed, hung from one =
side of your >engine. This would work, and you would prolly have a cog =
belt drive arrangement as a result, if you wanted serious manifold =
pressure. Of course this will generate a new >force/belt vector load at =
the nose of the crank, that may or may not affect your front bearings. =
One might even direct the output of this large compressor to a single =
>inter/aftercooler device for post cooling.
>Let's consider a different approach......
>What about mounting two smaller centrifugals, low on the motor, =
perhaps directly opposed to the crank centerline so as to cancel the =
belt load vectors. Further imagine >the discharge(s) from these =
compressors being directed thru two parallel inter/aftercooler =
exchangers (ala: Porsche twin turbo setups). The twin intercoolers =
might be a >bit easier to position within a street vehicle. At an =
esoteric design level, twins could allow a person to fabricate an engine =
bay setup that has a symmetric and artful >appearance.
>Cost aside, does anyone see any further advantages/disadvantages to =
running two slightly smaller compressors in place of one larger unit? =
Obviously, the cost will be >higher with twins. I'm more wondering =
about airflow versus crank speed, throttle response, boost response =
profile, parasitic drain at a given combined flow/pressure, >etc. =20
>Thoughts would be appreciated;
>Walt.
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<BODY bgColor=3D#ffffff>
<DIV><FONT size=3D2>I like the concept and have been looking at =
something=20
similar. It seems that a large centrifugal supercharger would work =
okay,=20
but I don't like the pressure/flow (and thus) torque curve. The =
results=20
from a centrifugal unit are something like the square of the tip =
speed. If=20
the diameter of the charger is larger then the tip speed can be =
accomplished=20
with a lower RPM. I've been looking at gearing directly to the =
crank, as=20
opposed to belt drive. The cam is a VERY high and variable load to =
the=20
crank and seems to be handled quite well</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>I like the concept of some type of variable =
gearing. The=20
early Paxtons (?) did this by changing the driven pulley diameter. =
Mainly=20
I'd like to have a much broader torque range than would be available =
with the=20
current engine centrifugal super chargers.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>dh</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dwsherwin at home.com href=3D"mailto:wsherwin at home.com">Walter =
Sherwin</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dgmecm at diy-efi.org=20
href=3D"mailto:gmecm at diy-efi.org">gmecm at diy-efi.org</A> ; <A=20
title=3Ddiy_efi at diy-efi.org=20
href=3D"mailto:diy_efi at diy-efi.org">diy_efi at diy-efi.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Friday, April 13, 2001 =
12:25=20
AM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Twin Centrifugals VS=20
Single</DIV>
<DIV><BR></DIV>
<DIV><FONT size=3D2>Forwarded from another list.....</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT><BR></DIV>
<DIV><FONT size=3D2>>Here's something I've been tossing around in =
my mind,=20
for street toy use, and I'd love to hear more from the=20
group........</FONT></DIV>
<DIV><FONT size=3D2></FONT><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>>Let's say you have a large displacement =
stroker motor,=20
and you desire to artificially stuff it's hunger with centrifugal=20
supercharging (non manufacturer specific at this >point). The =
typical=20
approach today would be to seek out a largish single centrifugal unit =
that=20
would do the dirty job, and pulley it to gain the max =
desired air=20
flow/boost at >a specific engine speed. This would net =
you a=20
large diameter centrifugal, operating at a somewhat less than maximum =
impeller=20
speed, hung from one side of your >engine. </FONT><FONT =
size=3D2>This=20
would work, and you would prolly have a cog belt drive =
arrangement=20
as a result, if you wanted serious manifold pressure. Of course =
this=20
will generate a new >force/belt vector load at the nose of the =
crank, that=20
may or may not affect your front bearings. One might even direct =
the=20
output of this large compressor to a single >inter/aftercooler =
device for=20
post cooling.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>>Let's consider a different =
approach......</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>>What about mounting two smaller centrifugals, =
low on the=20
motor, perhaps directly opposed to the crank centerline so as to =
cancel the=20
belt load vectors. Further imagine >the discharge(s) from =
these=20
compressors being directed thru two parallel inter/aftercooler =
exchangers=20
(ala: Porsche twin turbo setups). The twin intercoolers might be =
a=20
>bit easier to position within a street vehicle. At an =
esoteric=20
design level, twins could allow a person to fabricate an engine =
bay setup=20
that has a symmetric and artful >appearance.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>>Cost aside, does anyone see any further=20
advantages/disadvantages to running two slightly smaller =
compressors in=20
place of one larger unit? Obviously, the cost will be >higher =
with=20
twins. I'm more wondering about airflow versus crank speed, =
throttle=20
response, boost response profile, parasitic drain at a given combined=20
flow/pressure, >etc. </FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>>Thoughts would be appreciated;</FONT></DIV>
<DIV><FONT size=3D2>>Walt.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT> </DIV></BLOCKQUOTE></BODY></HTML>
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