/6 Exhaust: Dual or single? Your thoughts

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good luck with the flow master 40. I put a 3" flow master(Ii don't recall the model), years ago, on my 67 cuda 360. It was tolerable, just putting around, but at WOT it was beyond extremely loud. It would catch the attention of any LEO within a mile, no joke.
 
Flowmaster mufflers suck. They sound good on the one thing they were invented for. A small block Fox Mustang.
 
rustycowll69 said:
I've run headers and true duals. I liked it. If you want nasty, I think you'll want duals.
Back in the day, Dodge and Plymouth had a high performance single exhaust, which really sounded mean, but I think it was only a v8 option. It had a baloney sliced big rectangular attenuator. As big, or bigger than 70 Cuda tip. I don't know why nobody repops those, they were awesome. If they sounded that good behind a six, I would conside one of those.
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They do. They are on the HP273 system on early A bodies. Accurate LTD makes the systems. Here's the link: Just scroll down. A-Body HiPo Exhaust System
Here's mine:
 
dirty white boy said:
always preferred a 2 stack pete than a one stack mack....i could impose a number of ryhmes with this but...gotta have my twice pipes like rest the kewl kids man...lol
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Then if you use true duals with an inline six like the slant, you're leaving a lot of torque on the table. But it'll look cool.
 
RustyRatRod said:
Then if you use true duals with an inline six like the slant, you're leaving a lot of torque on the table. But it'll look cool.
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how bout running single to back of cab and splitting there thats how most big truck do it coming off the single turbo outlet?
 
dirty white boy said:
how bout running single to back of cab and splitting there thats how most big truck do it coming off the single turbo outlet?
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You're missing the entire point. If you split dual on an inline, you're splitting backwards. That actually takes completely away from the scavenging effect.

You need to split two to one, not one to two.
 
RustyRatRod said:
You're missing the entire point. If you split dual on an inline, you're splitting backwards. That actually takes completely away from the scavenging effect.

You need to split two to one, not one to two.
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Actually in this case, he would have a double split, and the second would only have an effect on sound & velocity......if the second split is done efficiently................
Anywho.............until Deemo gets his headers, all the 6-2-1 talk is pointless, MORE important is that he is sure to pick headers that can accommodate a change to a 225
if he decides to switch, & there aren't a ton of choices if he sticks w/the 170.
 
Killer6 said:
Actually in this case, he would have a double split, and the second would only have an effect on sound & velocity......if the second split is done efficiently................
Anywho.............until Deemo gets his headers, all the 6-2-1 talk is pointless, MORE important is that he is sure to pick headers that can accommodate a change to a 225
if he decides to switch, & there aren't a ton of choices if he sticks w/the 170.
Click to expand...

Lets examine the slant six (or any American six's firing order) for that matter related to exhaust pulses and scavenging.

1-5-3-6-2-4 is the firing order for every American made inline six........unless some of the new ones are different.

This means that a slant with a 6 into 2 header is perfect for scavenging.

Why? Lets split the front three cylinders and the rear three.

Keep in mind, the firing order, 1-5-3-6-2-4.

See what's going on here? The firing order alternates between the front three and rear three every time a cylinder fires. This means with every firing of a cylinder, exhaust will be scavenged from the opposite cylinder on "the other three".

So, your "theory" is not optimal. This is why a good 6 into two header and into one large exhaust pipe works best here and duals do not.
 
RustyRatRod said:
Lets examine the slant six (or any American six's firing order) for that matter related to exhaust pulses and scavenging.

1-5-3-6-2-4 is the firing order for every American made inline six........unless some of the new ones are different.

This means that a slant with a 6 into 2 header is perfect for scavenging.

Why? Lets split the front three cylinders and the rear three.

Keep in mind, the firing order, 1-5-3-6-2-4.

See what's going on here? The firing order alternates between the front three and rear three every time a cylinder fires. This means with every firing of a cylinder, exhaust will be scavenged from the opposite cylinder on "the other three".

So, your "theory" is not optimal. This is why a good 6 into two header and into one large exhaust pipe works best here and duals do not.
Click to expand...
LOL!! Dude, I've preached & espoused this whole concept a bazillion times(even tho' the 6 into 1 header has dyno'd better), but re-think what was proposed above,......
running a single to the rear then splitting it for the "dual look", the front end of the system(with Dutras' or headers) will already have the correct split/merge incorporated...
.........get it??? Re-splitting it in the rear won't affect the scavenging one iota, it will simply redirect the single stream of gasses down two exits.
 
So not to get too geeky here, but the Surface Area of a 2.5 inch exhaust system is 4.9 inches. The Surface Area of a single 1.75 inch exhaust system is 2.4 inches. So a Siamese dual 1.75 inch system would be just a hair off of what a single 2.5 inch exhaust system at 4.8 inches. The presentation of of a Siamese system would absolutely killer, and the main benefit would probably be clearance.
Sorry,but that is inaccurate,allow me to to explain.First up,You are confusing surface
area w/ CROSS-SECTIONAL area,which is the dimension you stated.Secondly,the
inside dimensions are the ones you need to calculate for,which is approx. 1/8"less
for 90% of std. bendable exh. tubing and available in up to at least 12'sticks.
2.5"/ 1.75"x(2) / 1.125"x(6)

area) 4.43"sq./ 4.148"sq./ 4.71"sq.

circum.) 7.47" / 10.2" / 18.85"

surf.area/ 89.64"sq./ 122.4"sq./ 226.2"sq.
lin.ft.

It should be obvious the frictional area goes up w/multiple piping,even when the
cross-sectional area is the same,which I illustrated w/the 6 -1 1/8" pipe numbers.
This doesn't take into account frictional factors based on boundary layer shear &
tumble,which will remain constant on the surface regardless of pipe dia.This effect
will "shrink"the usable area of the pipe by approx. the same dimension,obviously
having a much more detrimental impact on smaller pipes than larger ones,which
have the mass fluid flow moving more freely in the center.
If ground clearance is an issue,you mite investigate Burns oval tubing as a much
better compromise,not cheap tho'.I like the center exh. exit concept,and you can
dual tip or Y-split two pipes out back if you use a single but like the "dual look".
Going to be a tite bit of work w/ the spare well there w/o it hanging low.Good luck
w/ the new place & let us know where you're at with this,I'm sure you know about
the factory offered pieces for that eng.,incl. a ported head etc., and FI means no
carb. air filter and the flexibility of something like pictured above, so hood issue
isn't as bad as it could be, Have fun!!!:coffee2:

Reposted from JohnFM3's 4.0L swap thread
 
Splitting after the initial wye slows velocity.

Killer6 said:
LOL!! Dude, I've preached & espoused this whole concept a bazillion times(even tho' the 6 into 1 header has dyno'd better), but re-think what was proposed above,......
running a single to the rear then splitting it for the "dual look", the front end of the system(with Dutras' or headers) will already have the correct split/merge incorporated...
.........get it??? Re-splitting it in the rear won't affect the scavenging one iota, it will simply redirect the single stream of gasses down two exits.
Click to expand...
 
No worries mate!, I simply wanted to clarify the correct science of flow to those
following this so they have the ammo for their own projects. I agree the aesthetic
of the siamese dual system ala BMW etc. looks cool,as does the center exit,tho'
you will have to be creative w/ the spare well rite there. I would also second the idea
of making your own X-pipe as close to the frt. as poss., that would give you the 6
into 2 into 1 benefit and allow for the siamese system.
I didn't remember if the factory "manifold" was the shorty 6-2-1 unit, and planned
on cutting the "Y" section out, then putting flanges on the pair? Later units,and now
most aftermarket units come with flex/expansion sections as they were notorious
for cracking(sure you saw plenty of those), which will probably require some sup-
port bracket .
Glad you're moved in,I'm sure we've all done that for ourselves,friends and our
families.It can be extra challenging for us gearheads!!
To address the carb. & OBD I, carbs are probably more sensitive than any EFI
system,and OBD I all had closed loop adaptive learn. GM's Block learn mem.etc.
The GM's & Fords w/mass air systems have a definite advantage over speed den-
sity systems because they read actual airflow in,not calculate it.Also the OBD I's
Open loop idle AND WOT! This takes out adaptability when WE would like most.
The solution for us OBD I speed density users is the adj. fuel press. regulator.
Dial up the press. to compensate for flow improvements etc., and the closed loop
operation will dial back the injector duty per the O2 sensors input at normal drive
conditions, usually within it's parameter's unless you make a drastic change,read
big cubes, super headwork etc. The Grand National guys lived on that method w/
stock system use.You only need a scanner & watch O2 readings at WOT,then adj.
I'm excited to see your progress on this,keep us posted!! :coffee2:

And that one......................................
 
Killer6 said:
Actually in this case, he would have a double split,
HELLO?
and the second would only have an effect on sound & velocity......if the second split is done efficiently................HELLO?
:D


Anywho.............until Deemo gets his headers, all the 6-2-1 talk is pointless, MORE important is that he is sure to pick headers that can accommodate a change to a 225
if he decides to switch, & there aren't a ton of choices if he sticks w/the 170.
Click to expand...
 
Rainy Day Auto said:
I am putting together a slant six valiant wagon with a hotter than stock six but I am still using a single exhaust. To me, most six cylinder engines sound just awful through duals. A 2.5 inch single exhaust set up should be plenty and still sound healthy.
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It's not about sound, it's about performance! 2bbl carburetor? What's the setup? if it's a 2bbl, 2.50" exhaust is all you need. I think it's funny because loud exhaust does not mean performance, usually the exact opposite. Port your heads and exhaust manifolds/and or upgrade to exhaust headers sometimes is all you need before larger pipes.
 
RustyRatRod said:
Lets examine the slant six (or any American six's firing order) for that matter related to exhaust pulses and scavenging.

1-5-3-6-2-4 is the firing order for every American made inline six........unless some of the new ones are different.

This means that a slant with a 6 into 2 header is perfect for scavenging.

Why? Lets split the front three cylinders and the rear three.

Keep in mind, the firing order, 1-5-3-6-2-4.

See what's going on here? The firing order alternates between the front three and rear three every time a cylinder fires. This means with every firing of a cylinder, exhaust will be scavenged from the opposite cylinder on "the other three".

So, your "theory" is not optimal. This is why a good 6 into two header and into one large exhaust pipe works best here and duals do not.
Click to expand...
Thank you for the understanding of the 6 cylinder...lets move on to 3rd grade math. 3+3=2...Anyone gets this? Without forced induction a straight six could get better performance than a V8. The straight six cycles exhaust better than the V. This is an advantage. A V8 will only be quieter when both banks are separate and both with a muffler, no V or X pipes from both banks splitting into mufflers will be quieter. It's rather simple science. You can find this in Chrysler nomenclature from at least 1972.
 
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RustyRatRod said:
Flowmaster mufflers suck. They sound good on the one thing they were invented for. A small block Fox Mustang.
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++++four stars to this post, flow masters sound like sh crap!
exoJL said:
I thought the boat anchor is the small block!! Let's go smaller...6 cylinder is better!
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I may be getting the wagon I posted about earlier. He finally texted me back and dropped the price $200, I told him I didn`t have that much $, and he said he`d consider my offer. Anyway, that being said, it has a big slant in it, and I will be redoing it, so I`ll be ratlling u guys cages maybe. I`m goin to go for drivability and gas milage , I`ve got an aprox. 700 horse form S, 68 barracuda, don` need another gas hog.
 
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