Kurt Horvath
11-04-2008, 04:31
Just a quick note to resolve any confusion. I never suggested the
pipes going from 6" to 5" diameter. The opposite has been referred to
in relation to the original BB pipes and muffler setup. That is 5"
pipes, 6" muffler inlet and outlet. 5" pipes traversing to a 5" or 6"
stack up through the exhaust tunnel is fine, but I have no idea how
going from 6" to 5" got into this thread.
What a engines needs is low backpressure, but high exhaust stream
velocity. A fast-moving but free-flowing gas column in the exhaust
helps create a rarefaction or a negative pressure wave behind the
exhaust valve as it opens. This vacuum helps scavenge the cylinder of
exhaust gas faster and more thoroughly with less pumping losses. An
exhaust pipe that is too big in diameter has low backpressure but
lower velocity. The low velocity reduces the effectiveness of this
scavenging effect, which has the greatest impact on low-end torque.
Low backpressure and high exhaust stream velocity can be achieved by
running straight-through free-flowing pipes. A well-designed, high-
performance exhaust system typically has about 2 to 6 psi of
backpressure. For an interesting comparison, an un-muffled straight
pipe on a real racecar usually has 1 to 3 psi of backpressure.
To get the least amount of backpressure, most of the good, high-
performance mufflers available today have what is called a straight-
through design. These mufflers quiet the exhaust by absorbing high-
frequency vibrations in heat-resistant packing, usually consisting of
stainless-steel mesh and heat-resistant ceramic fibers.
They typically have an inner core that is straight-through with no
baffling at all, much like a straight pipe with many small holes in
it. The pipe is louvered or perforated when it passes inside the
muffler's shell, allowing sound energy to pass through the holes but
leaving the exhaust gas flow unimpeded. You can see straight through
these types of mufflers. The louvered or perforated core is usually
wrapped with either fiberglass wadding (hence the old-school term,
Glass Pack) or, in the better mufflers, stainless-steel mesh backed
by ceramic fiber to help further absorb the sound. On straight-
through mufflers, the longer the muffler and the bigger the can, the
quieter it is. The length usually has no effect on backpressure, just
noise output.
Sounds Great!
Unfortunately the 5" Stack that I WAS having built is 5" outside
diameter, with a 3" interior straight through section. Poor
communication between me and the fabricator, similar to the 6" to 5"
error discussed in past posts.
A muffler designed with a 5" diameter core would have a 7" or 8"
outside diameter and is cost prohibitive in SS
New Options:
1 - Use two of these 5" stacks at doubled the cost.
2 - Go back to a standard muffler.
3 - Stainless Steel Muffler 5" in & out
4 - STRAIGHT PIPE
Because today is election day.
I'd like to throw this out there for a general vote.
What would your choice be???????
1, 2, 3, or 4
Thanks for all the help.
Kurt Horvath
95 PT 42
10AC
--- In WanderlodgeForum@yahoogroups.com, "Joyce and Richard Hayden"
wrote:
>
> Rob,
> The elbow I'm going to have to replace is the one that is 90deg+
going into the muffler. It's not a standard 90deg bend. My pyro
tube is just down wind of the turbo in the 180deg bend. The exh.
exits on the curb side.
>
> Dick Hayden - '87 PT 38 - Lake Stevens, WA
>
> ----- Original Message -----
> From: Rob Robinson
> To:
WanderlodgeForum@yahoogroups.com
> Sent: Monday, November 03, 2008 12:25 PM
> Subject: Re: [WanderlodgeForum] Re: 6" SS EXHAUST STACK
>
>
> Richard I just replaced that elbow you are speaking of. It
wasn't hard to find. In fact I had my supplier Mac Industrial Exhaust
Vancouver BC modify it with a longer end on the end that goes into
the pyro tube that goes directly into the turbo. Call me if you need
more info 250 590-8050
>
>
>
> 2008/11/3 Joyce and Richard Hayden
>
>
>
> Kurt & David and others who might be following this discussion
as I have.
>
> When you introduced the Bernoulli's Equation into this
discussion I figured it was time to ask my brother for help. He has
some background with advanced math and has been helpful to another of
our group in the past. I forwarded to him the messages at the bottom
to give him some background and data that had already been offered.
I notice now that this subject has died down somewhat so far today
but here is his message to me anyway. I am not going to pretend that
I understand all of it but it seems that going from 6" to 5" isn't
going to be the end of the world. I know you two have Series 60
engines and I have the older 8v92 but the problem is the same and I
have discovered a holds in the elbow that goes into the muffler.
That elbow is probably unobtainable or if it is would be quite
expensive. So, I was considering 5" as many others have.
>
> Any, here is my brother Steve Hayden's response to me -
unedited:
>
>
> Brother,
>
>
>
> You have stretched the limits of my memory on this one! The
last time I thought about fluid flow and the Bernoulli Principal was
probably 40 or so years ago. Not to worry; it is fun to fire up the
old neurons. I'll try to answer your question below. The response
isn't technically rigorous as some of your forum buddies may point
out. It does seem to make sense though.
>
>
>
> As I understand the question, it goes something like this. Does
changing the diameter of the exhaust system on the bus from six
inches to five inches result in any noticeable decrease in
performance? I understand that the exhaust system runs from the
manifolds to a turbocharger and then out through a muffler to the
atmosphere. If one constricts the exhaust from the outlet of the
turbocharger which results in a higher pressure at the output, then
the turbocharger efficiency decreases. Have I got that about right?
>
>
>
> If so, then the answer is changing from six inch diameter to
five inch is very unlikely to result in any detectable decrease in
performance. Here's the logic I used to reach this conclusion.
>
>
>
> To make the calculation, one uses one of the forms of
Bernoulli's Equation. I saw in one of the posts you sent me a
reference to a nice discussion of Bernoulli's Equation. This
discussion is correct in that it points out that Bernoulli's Equation
is an energy conservation equation which means you can't get
something for nothing. This equation only holds when no outside work
is being done on the system nor is the system doing any work on the
outside. Consequently, as was pointed out in the posting, the
Bernoulli Equation applies to the ideal situation of, for example,
non-compressible gas, laminar flow (non-turbulent), no friction with
the pipe walls and so on.
>
>
>
> Accounting for these non-ideal conditions from first principles
is tedious and usually results in equations that cannot be solved in
closed form. Engineers get around this by putting correction terms in
the equation and then determining the coefficients of the correction
terms by experimentation. This is a science within itself and not as
easy as I just made it sound. Fortunately, engineers have been
interested in fluid, including gas, flow in pipes for such
applications as gas and oil pipelines and have derived equations for
these applications. I did find an on-line calculator at
http://www.pipeflowcalculations.com/<http://www.pipeflowcalculations.c
om/> which I used to make my analysis.
>
>
>
> Of course, I had to make some assumptions to plug into the
calculator. With your help, I came up with the flowing. The amount of
exhaust gas that must be expelled out the exhaust pipe per unit time
was 24,000 liters/min. You estimated this from the displacement of
the engine cylinders times the number of cylinders times the rpm of
the engine. We also agreed that the length of pipe from the
turbocharger to the exhaust outlet at 7 feet and the temperature of
the exhaust at 500 F. I assumed the exhaust pipe was smooth with a
roughness of lest than one thousandth of an inch. The local
resistance coefficient which accounts for bends in the exhaust pipe
and other local constraints was tougher. I used the calculator
default value of 1 but also did a sensitivity analysis.
>
>
>
> Since the pressure at the exhaust pipe outlet is atmospheric
(14.7 psi), I calculated the pressure drop from the turbocharger
outlet to atmosphere along the length of the exhaust pipe for
different pipe diameters. The result is shown graphically below.
>
>
>
>
>
>
>
> Note that the pressure drop axis is logarithmic. So the
difference in pressure drop between a 5 and 6 inch diameter pipe is
only about 0.15 psi. In fact, the pressure drop is less than 1 psi
for exhaust pipes 3.5 inches and larger.
>
>
>
> I did change the local resistance coefficient to see the
effect. At the default value of 1 and for a 5 inch diameter pipe, the
pressure drop is 0.25 psi. An order of magnitude less at 0.1 results
in a pressure drop of 0.09 psi and an order of magnitude larger at
10, 1.8 psi.
>
>
>
> I don't know what the pressure at the turbocharger input is but
seems unlikely that a pressure change of 1 psi or less at the
turbocharger output would result in a detectable decrease in
performance. Perhaps someone on your forum has this number.
>
>
>
> Since many systems are over designed to have a safety margin,
it also seems to make sense that changing to 5 inch diameter from 6
inch should make little difference.
>
>
>
> Hope this helps. Feel free to cut and paste onto the forum if
you like. Any questions, you know where I live.
>
>
>
> Steve
>
>
>
>
> ----- Original Message -----
> From: Kurt Horvath
> To:
WanderlodgeForum@yahoogroups.com
> Sent: Friday, October 31, 2008 8:24 PM
> Subject: [WanderlodgeForum] Re: 6" SS EXHAUST STACK
>
>
>
> 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<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@yahoogroups.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/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->>
> > > > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
>
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->>>
> > > > > 89.pdf
> > > > > > >
> <http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->>
> > > > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
>
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_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?>>>
> > > > > > >
<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@yahoogroups.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
> > >
> >
>
>
>
>
>
>
>
>
> --
> Rob, Sue & Merlin Robinson
> 94 WLWB
>
pipes going from 6" to 5" diameter. The opposite has been referred to
in relation to the original BB pipes and muffler setup. That is 5"
pipes, 6" muffler inlet and outlet. 5" pipes traversing to a 5" or 6"
stack up through the exhaust tunnel is fine, but I have no idea how
going from 6" to 5" got into this thread.
What a engines needs is low backpressure, but high exhaust stream
velocity. A fast-moving but free-flowing gas column in the exhaust
helps create a rarefaction or a negative pressure wave behind the
exhaust valve as it opens. This vacuum helps scavenge the cylinder of
exhaust gas faster and more thoroughly with less pumping losses. An
exhaust pipe that is too big in diameter has low backpressure but
lower velocity. The low velocity reduces the effectiveness of this
scavenging effect, which has the greatest impact on low-end torque.
Low backpressure and high exhaust stream velocity can be achieved by
running straight-through free-flowing pipes. A well-designed, high-
performance exhaust system typically has about 2 to 6 psi of
backpressure. For an interesting comparison, an un-muffled straight
pipe on a real racecar usually has 1 to 3 psi of backpressure.
To get the least amount of backpressure, most of the good, high-
performance mufflers available today have what is called a straight-
through design. These mufflers quiet the exhaust by absorbing high-
frequency vibrations in heat-resistant packing, usually consisting of
stainless-steel mesh and heat-resistant ceramic fibers.
They typically have an inner core that is straight-through with no
baffling at all, much like a straight pipe with many small holes in
it. The pipe is louvered or perforated when it passes inside the
muffler's shell, allowing sound energy to pass through the holes but
leaving the exhaust gas flow unimpeded. You can see straight through
these types of mufflers. The louvered or perforated core is usually
wrapped with either fiberglass wadding (hence the old-school term,
Glass Pack) or, in the better mufflers, stainless-steel mesh backed
by ceramic fiber to help further absorb the sound. On straight-
through mufflers, the longer the muffler and the bigger the can, the
quieter it is. The length usually has no effect on backpressure, just
noise output.
Sounds Great!
Unfortunately the 5" Stack that I WAS having built is 5" outside
diameter, with a 3" interior straight through section. Poor
communication between me and the fabricator, similar to the 6" to 5"
error discussed in past posts.
A muffler designed with a 5" diameter core would have a 7" or 8"
outside diameter and is cost prohibitive in SS
New Options:
1 - Use two of these 5" stacks at doubled the cost.
2 - Go back to a standard muffler.
3 - Stainless Steel Muffler 5" in & out
4 - STRAIGHT PIPE
Because today is election day.
I'd like to throw this out there for a general vote.
What would your choice be???????
1, 2, 3, or 4
Thanks for all the help.
Kurt Horvath
95 PT 42
10AC
--- In WanderlodgeForum@yahoogroups.com, "Joyce and Richard Hayden"
>
> Rob,
> The elbow I'm going to have to replace is the one that is 90deg+
going into the muffler. It's not a standard 90deg bend. My pyro
tube is just down wind of the turbo in the 180deg bend. The exh.
exits on the curb side.
>
> Dick Hayden - '87 PT 38 - Lake Stevens, WA
>
> ----- Original Message -----
> From: Rob Robinson
> To:
WanderlodgeForum@yahoogroups.com
> Sent: Monday, November 03, 2008 12:25 PM
> Subject: Re: [WanderlodgeForum] Re: 6" SS EXHAUST STACK
>
>
> Richard I just replaced that elbow you are speaking of. It
wasn't hard to find. In fact I had my supplier Mac Industrial Exhaust
Vancouver BC modify it with a longer end on the end that goes into
the pyro tube that goes directly into the turbo. Call me if you need
more info 250 590-8050
>
>
>
> 2008/11/3 Joyce and Richard Hayden
>
>
> Kurt & David and others who might be following this discussion
as I have.
>
> When you introduced the Bernoulli's Equation into this
discussion I figured it was time to ask my brother for help. He has
some background with advanced math and has been helpful to another of
our group in the past. I forwarded to him the messages at the bottom
to give him some background and data that had already been offered.
I notice now that this subject has died down somewhat so far today
but here is his message to me anyway. I am not going to pretend that
I understand all of it but it seems that going from 6" to 5" isn't
going to be the end of the world. I know you two have Series 60
engines and I have the older 8v92 but the problem is the same and I
have discovered a holds in the elbow that goes into the muffler.
That elbow is probably unobtainable or if it is would be quite
expensive. So, I was considering 5" as many others have.
>
> Any, here is my brother Steve Hayden's response to me -
unedited:
>
>
> Brother,
>
>
>
> You have stretched the limits of my memory on this one! The
last time I thought about fluid flow and the Bernoulli Principal was
probably 40 or so years ago. Not to worry; it is fun to fire up the
old neurons. I'll try to answer your question below. The response
isn't technically rigorous as some of your forum buddies may point
out. It does seem to make sense though.
>
>
>
> As I understand the question, it goes something like this. Does
changing the diameter of the exhaust system on the bus from six
inches to five inches result in any noticeable decrease in
performance? I understand that the exhaust system runs from the
manifolds to a turbocharger and then out through a muffler to the
atmosphere. If one constricts the exhaust from the outlet of the
turbocharger which results in a higher pressure at the output, then
the turbocharger efficiency decreases. Have I got that about right?
>
>
>
> If so, then the answer is changing from six inch diameter to
five inch is very unlikely to result in any detectable decrease in
performance. Here's the logic I used to reach this conclusion.
>
>
>
> To make the calculation, one uses one of the forms of
Bernoulli's Equation. I saw in one of the posts you sent me a
reference to a nice discussion of Bernoulli's Equation. This
discussion is correct in that it points out that Bernoulli's Equation
is an energy conservation equation which means you can't get
something for nothing. This equation only holds when no outside work
is being done on the system nor is the system doing any work on the
outside. Consequently, as was pointed out in the posting, the
Bernoulli Equation applies to the ideal situation of, for example,
non-compressible gas, laminar flow (non-turbulent), no friction with
the pipe walls and so on.
>
>
>
> Accounting for these non-ideal conditions from first principles
is tedious and usually results in equations that cannot be solved in
closed form. Engineers get around this by putting correction terms in
the equation and then determining the coefficients of the correction
terms by experimentation. This is a science within itself and not as
easy as I just made it sound. Fortunately, engineers have been
interested in fluid, including gas, flow in pipes for such
applications as gas and oil pipelines and have derived equations for
these applications. I did find an on-line calculator at
http://www.pipeflowcalculations.com/<http://www.pipeflowcalculations.c
om/> which I used to make my analysis.
>
>
>
> Of course, I had to make some assumptions to plug into the
calculator. With your help, I came up with the flowing. The amount of
exhaust gas that must be expelled out the exhaust pipe per unit time
was 24,000 liters/min. You estimated this from the displacement of
the engine cylinders times the number of cylinders times the rpm of
the engine. We also agreed that the length of pipe from the
turbocharger to the exhaust outlet at 7 feet and the temperature of
the exhaust at 500 F. I assumed the exhaust pipe was smooth with a
roughness of lest than one thousandth of an inch. The local
resistance coefficient which accounts for bends in the exhaust pipe
and other local constraints was tougher. I used the calculator
default value of 1 but also did a sensitivity analysis.
>
>
>
> Since the pressure at the exhaust pipe outlet is atmospheric
(14.7 psi), I calculated the pressure drop from the turbocharger
outlet to atmosphere along the length of the exhaust pipe for
different pipe diameters. The result is shown graphically below.
>
>
>
>
>
>
>
> Note that the pressure drop axis is logarithmic. So the
difference in pressure drop between a 5 and 6 inch diameter pipe is
only about 0.15 psi. In fact, the pressure drop is less than 1 psi
for exhaust pipes 3.5 inches and larger.
>
>
>
> I did change the local resistance coefficient to see the
effect. At the default value of 1 and for a 5 inch diameter pipe, the
pressure drop is 0.25 psi. An order of magnitude less at 0.1 results
in a pressure drop of 0.09 psi and an order of magnitude larger at
10, 1.8 psi.
>
>
>
> I don't know what the pressure at the turbocharger input is but
seems unlikely that a pressure change of 1 psi or less at the
turbocharger output would result in a detectable decrease in
performance. Perhaps someone on your forum has this number.
>
>
>
> Since many systems are over designed to have a safety margin,
it also seems to make sense that changing to 5 inch diameter from 6
inch should make little difference.
>
>
>
> Hope this helps. Feel free to cut and paste onto the forum if
you like. Any questions, you know where I live.
>
>
>
> Steve
>
>
>
>
> ----- Original Message -----
> From: Kurt Horvath
> To:
WanderlodgeForum@yahoogroups.com
> Sent: Friday, October 31, 2008 8:24 PM
> Subject: [WanderlodgeForum] Re: 6" SS EXHAUST STACK
>
>
>
> 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<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@yahoogroups.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/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->>
> > > > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
>
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->>>
> > > > > 89.pdf
> > > > > > >
> <http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->>
> > > > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_03_pg70->
>
> > >
<http://www.dynaflexproducts.com/download...g_03_pg70-
<http://www.dynaflexproducts.com/download...g_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?>>>
> > > > > > >
<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@yahoogroups.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
> > >
> >
>
>
>
>
>
>
>
>
> --
> Rob, Sue & Merlin Robinson
> 94 WLWB
>