6" SS EXHAUST STACK

[David Brady]

Hi Kurt,



I am for hollow unbaffled straight pipes. The Bernoulli effect,

or "crimp" is built into the turbocharger. Take a look, every

one I've seen has the exhaust tapering to a smaller diameter

as it passes the turbine to increase velocities. I'm suggesting

that performance may be enhanced by providing a taper from

the outlet of the turbo exhaust thru the exhaust system. Our

taper is a 5" pipe at going into 6" pipe; that's a surface area of

19.6 sq inches expanding to 28.3 square inches. Basically a horn

hanging from the outlet of the exhaust turbo enhancing the flow

of gases from the turbo. I'm not surprised the vendors support your

desire for a 5" exhaust. The only way to really get at the bottom

of this is to try both and dyno both.



David Brady

'02 LXi, NC



Kurt Horvath wrote:

David,



A few days ago you were all for a straight pipe.



Now we have delved into the effects and merits of the, "Bernoulli

effect" it presumes that the density of the flowing gas is constant,

which will not necessarily be true in this application.



If this were a consideration and a factor in design and function

wouldn't this be a standard application on all exhausts, considering

today's drive for better performance Vs energy expended Vs

particulate

matter expelled Vs whatever else the EPA thinks we should be

ejecting from our exhaust pipes?



One factor you may have not considered are the exhaust blankets I

mentioned. They will retain the heat within the pipes thus increasing

the velocity of the exhaust creating an accelerated flow of gasses

through the tubes.



If I may present another observation, 5" exhaust systems are the

standard on all production class 8 trucks.



Furthermore and for the heck of it I don't believe that the trucker

that has 8" stacks on his rig has considered the, "Bernoulli effect"

in his choice at the Chrome Shop. Although it mat have an effect on

performance further than just looking cool. They do look good, no

doubt.



For the last four weeks I have queried Detroit Diesel, Custom Exhaust

Fabricators, Several OEM Exhaust Mfg.'s, Marine Exhaust Engineers &


Fabricators, My BB Guru, and anyone else that would lend an ear, and

no one has expressed any apprehension or regard in the respect to a

5" exhaust system. In fact all parties expressed their surprise in

respect as to why the system would change size at the muffler.



Several owners have modified their systems to 5" from end to end, and

have seen no change in performance. Positive or negative, In general

it was just a matter of convenience in acquiring parts, I won't get

into that. That has recently been beaten to death at the expense of

all parties involved



If there is someone who would like to further this debate with

Imperical evidence of the merits of, or placing a venturi somewhere

in this exhaust system I have pasted a site below where you can

formulate your calculations. I would love to see some evidence of a

positive effect, in which case I would have no problem in adding a

venturi crimp in the exhaust system.



Bernoulli Calculation



http://hyperphysics.phy-astr.gsu.edu/Hbase/pber.html#beq



The calculation of the "real world" pressure in a constriction of a

tube is difficult to do because of viscous losses, turbulence, and

the assumptions which must be made about the velocity profile (which

affect the calculated kinetic energy). The model calculation here

assumes laminar flow (no turbulence), assumes that the distance from

the larger diameter to the smaller is short enough that viscous

losses can be neglected, and assumes that the velocity profile

follows that of theoretical laminar flow. Specifically, this involves

assuming that the effective flow velocity is one half of the maximum

velocity, and that the average kinetic energy density is given by one

third of the maximum kinetic energy density.



Now if you can swallow all those assumptions, you can model* the flow

in a tube where the volume flow rate is = cm3/s and the fluid density

is ñ = gm/cm3. For an inlet tube area A1= cm2 (radius r1 =cm), the

geometry of flow leads to an effective fluid velocity of v1 =cm/s.

Since the Bernoulli equation includes the fluid potential energy as

well, the height of the inlet tube is specified as h1 = cm. If the

area of the tube is constricted to A2=cm2 (radius r1 = cm), then

without any further assumptions the effective fluid velocity in the

constriction must be v2 = cm/s. The height of the constricted tube

is specified as h2 = cm.



The kinetic energy densities at the two locations in the tube can now

be calculated, and the Bernoulli equation applied to constrain the

process to conserve energy, thus giving a value for the pressure in

the constriction. First, specify a pressure in the inlet tube:

Inlet pressure = P1 = kPa = lb/in2 = mmHg = atmos.

The energy densities can now be calculated. The energy unit for the

CGS units used is the erg.



Inlet tube energy densities

Kinetic energy density = erg/cm3

Potential energy density = erg/cm3

Pressure energy density = erg/cm3

Constricted tube energy densities

Kinetic energy density = erg/cm3

Potential energy density = erg/cm3

Pressure energy density = erg/cm3





The pressure energy density in the constricted tube can now be

finally converted into more conventional pressure units to see the

effect of the constricted flow on the fluid pressure:



Calculated pressure in constriction =

P2= kPa = lb/in2 = mmHg = atmos.



This calculation can give some perspective on the energy involved in

fluid flow, but it's accuracy is always suspect because of the

assumption of laminar flow. For typical inlet conditions, the energy

density associated with the pressure will be dominant on the input

side; after all, we live at the bottom of an atmospheric sea which

contributes a large amount of pressure energy. If a drastic enough

reduction in radius is used to yield a pressure in the constriction

which is less than atmospheric pressure, there is almost certainly

some turbulence involved in the flow into that constriction.

Nevertheless, the calculation can show why we can get a significant

amount of suction (pressure less than atmospheric) with

an "aspirator" on a high pressure faucet. These devices consist of a

metal tube of reducing radius with a side tube into the region of

constricted radius for suction.



*Note: Some default values will be entered for some of the values as

you start exploring the calculation. All of them can be changed as a

part of your calculation.



Kurt Horvath

95 PT 42

10AC



> > > >

> > > > --- In "WanderlodgeForum%40yahoogroups.com"


> > <"Wanderlodge"Forum%40yahoogroups.com>

> > > > <"Wanderlodge"Forum%40yahoogroups.com>,
David Brady



> > > > wrote:

> > > > >

> > > > > Hi Kurt,

> > > > >

> > > > > No thanks, I already have a stock muffler.
Thanks for the

links,

> > > > > there's some pretty nifty items there. Be
careful with

those fancy

> > > > > braided stainless steel pieces. They look
sharp, but

they've always

> > > > > leaked on my turbocharged subaru wrx. Kurt,
you've been

around

> > > > > a few over-the-road coaches, Prevost' and what
not, what do

they

> > > > > run on their exhaust systems; i.e., expansion
pipes, flex

pipe, etc.

> > > > >

> > > > > David Brady

> > > > > '02 LXi, NC

> > > > >

> > > > > Kurt Horvath wrote:

> > > > > >

> > > > > > David, Would you like to take that brand
new muffler off

my

> > > > hands???

> > > > > >

> > > > > > According to DD straight pipe & ECU
will not have any

issues in

> > > > the

> > > > > > 95 vintage S 60.

> > > > > >

> > > > > > OEM built that pipe for BB ACAP - As
Cheep As Possible -

> > > > > >

> > > > > > The original routing of the pipe leaves
the turbo, source

of the

> > > > > > first failure, cracked the 1st 90 degree
turn a short

straight run

> > > > > > 2nd. 90 degree turn, then into a double
ball connector

that also

> > > > > > telescopes in and out. You can check out
that piece of S--

-, sorry

> > > > > > engineering wonder here.

> > > > > >

> > > > > >

http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70-


> > <http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70->

> > > > <http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70-



> > <http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70->>

> > > > 89.pdf

> > > > > >

<http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70-


> > <http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70->

> > > > <http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70-



> > <http://www.dynaflexproducts.com/downloads/DP_Catalog_03_pg70->>

> > > > 89.pdf>

> > > > > >

> > > > > > Page 76 Double Ball Joint with Slip Joint
Feature

Allowing Lateral

> > > > > > Movement length 16 to 18 inches mine
measures 14 .55

inches at

> > > > > > present. This marvel allows for 10
degrees of angularity

360

> > > > degree

> > > > > > rotation 2" of offset 2" axial movement,.
Hell the u

joints can't

> > > > > > move around that much. Besides it was
hard clamped to the

mount

> > > > from

> > > > > > the engine in front of this connection
not to mention

rusted to

> > > > the

> > > > > > point that it took an pneumatic impact
chisel to get it

apart.. So

> > > > > > what's the point. You need flex in
between the turbo and

the first

> > > > > > mount.

> > > > > >

> > > > > > The Flex Connector with liner I choose is
here at

> > > > > >

> > > > > > http://vibrantperformance.com/catalog/product_info.php?


> > <http://vibrantperformance.com/catalog/product_info.php?>

> > > > <http://vibrantperformance.com/catalog/product_info.php?


> > <http://vibrantperformance.com/catalog/product_info.php?>>

> > > > > > <http://vibrantperformance.com/catalog/product_info.php?


> > <http://vibrantperformance.com/catalog/product_info.php?>

> > > > <http://vibrantperformance.com/catalog/product_info.php?


> > <http://vibrantperformance.com/catalog/product_info.php?>>>

> > > > > >

> > > >

cPath=1022_1035_1064_1114&products_id=1008&osCsid=999d7ef5fdd15864bae3

> > > > > > 3db41abf5ef9

> > > > > >

> > > > > > The 2 90 degree turns were fabricated in
that manner

because it's

> > > > not

> > > > > > easy to bend large diameter pipe in a
single 180 degree

bend, thus

> > > > > > they weld 2 90's together, which is the
industry standard

for

> > > > > > manufacturing a 180 degree turn in large
pipe exhausts.

Well this

> > > > > > ain't the factory and we're not
constrained by what is

easy. I

> > > > have

> > > > > > acquired a 14ga 180 degree U-Tube that
has the same

external

> > > > > > dimensions as the original pipe. I'm not
an engineer but I

> > > > reasonably

> > > > > > certain that with the remaining 90 degree
bend and a 45

degree

> > > > bend

> > > > > > there will be sufficient back pressure.

> > > > > >

> > > > > > There will also be a flexible pipe hanger
mount behind

the Flex

> > > > > > connector mounted on the ceiling of the
engine

compartment that

> > > > will

> > > > > > support the middle section of pipe and
will allow for any

movement

> > > > > > and or torque that may be transferred to
the pipe by the

motor.

> > > > The

> > > > > > original clamps for the muffler have to
go as they are 6"

but the

> > > > > > rubber isolated mounting bars will remain
and that's all

that was

> > > > > > there to begin with. So where's the rub?
Bub!

> > > > > >

> > > > > > Not to take anything away from the
engineers that

designed the

> > > > Bird,

> > > > > > But there are some glaring deficiencies.
7 way trailer

plug, Air

> > > > > > Purge System, Watts valve, Accelerator
and Brake peddles,

Front

> > > > Left

> > > > > > Shock Mount, Relay for Jake Brake, W/D
Vent for Slendide

2000,

> > > > > > Installation of Refrigerator with
inadequate convection,

The seat

> > > > > > belts mounted to floor instead of the
seat, That reminds

me I

> > > > still

> > > > > > have to fix that one. Nothing like
hitting a road

transition just

> > > > to

> > > > > > have the air ride seat bounce and the
seat belts

automatically

> > > > adjust

> > > > > > for the slack then the air ride seat
rebounds and the

belts try to

> > > > > > cut you in half at the waist. That's just
the 95 PT 42.

I'm not

> > > > > > bitchin! I'm fixin

> > > > > >

> > > > > > Kurt Horvath

> > > > > > 95 PT 42

> > > > > > 10AC

> > > > > >

> > > > > > --- In "WanderlodgeForum%40yahoogroups.com"


> > <"Wanderlodge"Forum%40yahoogroups.com>

> > > > <"Wanderlodge"Forum%40yahoogroups.com>

> > > > > > <"Wanderlodge"Forum%40yahoogroups.com>,
David Brady



> > > > > > wrote:

> > > > > > >

> > > > > > > Kurt,

> > > > > > >

> > > > > > > I agree with Greg. I'm gonna keep
mine stock. There's a

bunch

> > > > > > > of vibration and movement back
there. I figure BB's been

> > > > building

> > > > > > > buses a whole lot longer than I
have. Initially I'd

scratch my

> > > > > > > head when looking at the frame and
support pieces, but

when

> > > > > > > you consider that something as big
as a bus must twist

and flex,

> > > > > > > this flexibility needs to be
designed in. Make one piece

> > > > stronger

> > > > > > > and you've created a stress raiser
someplace else.

> > > > > > >

> > > > > > > I have a friend who transplanted a
honda v-tech motor

into a

> > > > > > > lotus elise. Everything worked but
the alternator

mount. The

> > > > mount

> > > > > > > insists on cracking. There can be
some weird harmonics

and

> > > > > > > resonant frequencies going on that
are difficult to

grasp and

> > > > > > > only trial and error and a 50 year
track record of

building

> > > > buses

> > > > > > > can solve (unless you can model it
and run high powered

> > > > > > > computer finite element analysis on
it). He's still

fighting

> > > > that

> > > > > > > mount...

> > > > > > >

> > > > > > > Okay, I'm off my soap box.

> > > > > > >

> > > > > > > David Brady

> > > > > > > '02 LXi, NC

> > > > > > >

> > > > > > > Gregory OConnor wrote:

> > > > > > > >

> > > > > > > > Kurt, try and figure why there
were 4 bends. it may

be that

> > > > it was

> > > > > > > > engineered to alow for swing
room between the 'hung

exhaust'

> > > > and

> > > > > > > > the 'torque reaction of the
ruber mounted detroit'.

look at

> > > > the

> > > > > > roll

> > > > > > > > of the torque and see that
there is a place for the

movement

> > > > to

> > > > > > twist

> > > > > > > > a union. I kinda think this
movement was the problem

with the

> > > > > > > > resulting crack.

crack=result ;movement=cause ;facilitate

> > > > movement

> > > > > > > > =repair. may be that BB
enginered it correct but

someone

> > > > > > > > overtightened a band to cure an
exhaust leak???????

you also

> > > > got

> > > > > > to

> > > > > > > > keep the stack from
cantilivering off of the maniford

with

> > > > your

> > > > > > new

> > > > > > > > design. Scavenging is one
variable in fuel

efficiency. even

> > > > > > straight

> > > > > > > > pipes some time will result in
lower fuel economy

because the

> > > > > > intake

> > > > > > > > variable get screwd.
backpressure is mathed into the

computer.

> > > > > > > >

> > > > > > > >

> > > > > > > > ------------------------------------------------------

----

> > > > > > ------

> > > > > > > >

> > > > > > > > Internal Virus Database is
out-of-date.

> > > > > > > > Checked by AVG.

> > > > > > > > Version: 7.5.405 / Virus
Database: 270.8.0/1715 -

Release

> > > > Date:

> > > > > > 10/9/2008 12:00 AM

> > > > > > > >

> > > > > > >

> > > > > >

> > > > > >

> > > > > > ----------------------------------------------------------

> > > > ------

> > > > > >

> > > > > > Internal Virus Database is out-of-date.

> > > > > > Checked by AVG.

> > > > > > Version: 7.5.405 / Virus Database:
270.8.0/1715 - Release

Date:

> > > > 10/9/2008 12:00 AM

> > > > > >

> > > > >

> > > >

> > > >

> > > >

> > ----------------------------------------------------------

> > > >

> > > > Internal Virus Database is out-of-date.

> > > > Checked by AVG.

> > > > Version: 7.5.405 / Virus Database: 270.8.0/1715 -
Release

Date:

> > 10/9/2008 12:00 AM

> > > >

> > >

> >

> >

> > ----------------------------------------------------------

------

> >

> > Internal Virus Database is out-of-date.

> > Checked by AVG.

> > Version: 7.5.405 / Virus Database: 270.8.0/1715 - Release
Date:

10/9/2008 12:00 AM

> >

>

Internal Virus Database is out-of-date.

Checked by AVG. Version: 7.5.405 / Virus Database: 270.8.0/1715 - Release Date: 10/9/2008 12:00 AM