[s-cars] exhaust diameters

Steve Marinello smarinel at neosoft.com
Fri Sep 8 12:07:45 EDT 2000


If you look at some of the Dynomax info for their UltraFlo straight through
mufflers, you will see that the single inlet/dual outlet equivalent to a "Y"
split in the pipe actually INCREASES backpressure when compare to some
apps... as the flowrate is greater for the single/single application.

A 3" straight through or center/offset single seems to offer the best flow
at 2200+ cfm, while the double offset at opposite ends is the worst for the
singles (755 cfm).  The info is somehwt confusing because all single 2 1/2"
apps seem to provide 1,133 cfm throughput.  For comparison, the single 3"
in/dual 2 1/2" out is somewhere in between at 1400 cfm.

Check out a-1 performance.com and look at the Ultraflo Welded page for the
flow numbers.  You can call (800) 594-9815 to talk to a knowledgeable tech
guy about it.


Steve Marinello

----- Original Message -----
From: "Chris Covington" <malth at umich.edu>
To: <qshipq at aol.com>
Cc: <C1J1Miller at aol.com>; <s-car-list at egroups.com>; <quattro at audifans.com>
Sent: Friday, September 08, 2000 8:56 AM
Subject: Re: [s-cars] exhaust diameters


> On Fri, 8 Sep 2000 qshipq at aol.com wrote:
>
> > After doing a couple dozen of these systems over the years at my shop,
the
> > dual 2.5in system definitely makes a difference over a 3in.  I've tested
a
> > couple back to back, and the dual 2.5 in terms of flow and performance
is the
> > meow.  The math would show that a 4.0in single would flow even more,
someone
> > else will have to btdt, I've seen that on a car (buick GNX), can you say
> > stove pipe?
> > :)
>
> How about dual 3" or 2.75"?  If 4" is too big to fit on our cars, these
> should be doable.
>
> Heh, or triple 2.5" since we don't really have true dual exhaust anyway
> (unless you have a new S4 or something with a V engine or two
> 'downpipes').
>
> I have to wonder about this whole penchant for "dual" exhaust systems.
> We have inline engines.  Any muscle car guy, like me, would laugh when you
> say our Y systems are "dual exhaust."  Do that simple volumetric math,
> triple should be even better right?  Triple exhaust anyone? ;)
>
> But seriously, since there is a Y, a "split" in the exhaust, those
> mathematical formulae shouldn't apply for our I-5 engines.
> They are intended for two sources, not only one.  Yes, X and H pipes help
> on true dual exhausts, but these are entirely different than one pipe from
> an inline engine splitting into two.  Any Thermo Engineers / MSEs here?
> I'm a Computer Engineer, only took thermo, but I'd like some perspective
> on this.
>
> If that is true, and Y splits in exhausts are so great - then why don't
> all the high po V8/V6 etc. guys have quad exhausts when they have no
> expenses to spare, and no fabrication that can't be done?  The weight, I'm
> sure - and we're adding more with "dual" exhausts on our 200s.  Something
> to consider, along with this "math" that's being offered.  Maybe that's
> why there aren't many "dual" systems out there.
>
> Chris
> '91 2cq
>
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