Why dual exhaust?

[MHISSTC]

I had too much time to think recently and would like others opinions.

:?: Why are dual exhausts a popular performance upgrade? Couldn't the same thing be accomplished by properly sizing and routing a single exhaust?

I'm sure single exhausts are popular from the factory mainly because it's cost effective since roughly half the number of parts are needed. This single exhaust is fine for production vehicles with factory exhaust manifolds and no mods, but can provide inadequate flow when performance mods are added and the engine needs to breath better. When performance mods are added to a car with factory dual exhausts, the factory dual system can also become inadequate.

I'm speculating that the "old school" dual exhausts are popular because they are "easier" to install when also installing long tube headers because the exhaust can be routed straight back without having to worry about interfering with the driveline or creating ground clearance issues when routing around the driveline. The pipe size for a dual exhaust is also smaller than would be needed to flow the same volume of exhaust as a single pipe, thus eliminating potential under car clearance issues that may arise with a large singe pipe.

Modern dual exhausts incorporate such things as H-pipe and X-pipe crossovers in order to equalize pressures and help scavenging between the two pipes that lead back from the headers and cats into the mufflers and tailpipes.

:idea: My thinking is that if you design a system that leads from the headers into high flow cats and then a single y-pipe with pipe of sufficient size that all leads into the single muffler and tailpipe all sized properly to sufficiently flow the volume of exhaust required, you could come up with a single pipe exhaust system that would be equally as efficient as a more complex dual exhaust system with a crossover, but one that would require less parts and labor to create.

What do you all think?

[1hot86gt]

i dont know :| but 2 2 1/2 chrome tailpipes looks a whole lot better than 1 big tail pipe coming out the back :lol:

[mfpmax]

Most people do it cause "thats the thing to do", others don't like the sound of a single exhaust.

A single exhaust setup won't sound the same as a true dual setup. Take the F-Body for example...sounds NOTHING like a Mustang...of course there are factors that come into play like its engine and etc...but the big thing is they use a single pipe that comes from the engine, then goes into a muffler with twin outlets.

Two cars coming from a mile away...you can tell which one has dual exhaust.



And another reason...how many single exhaust "performance upgrade kits" do you see on the market.

[Evil86lx]

Dual exhaust even's out the exhaust pulse...

You can run single in a turbo application cause the turbo even's the exhaust pulse's..

By evening it out i mean it cleans it up and lets it flow at a higher rate letting the exhaust exit faster..

82 to present camaor's are one single 3inch pipe to one muffler and two pipes out. seems to work pretty well cause they make fairly good power..

kyle

[FunkRider82]

Lets do some math here.
A=R(1in)xR(1in)xPi=3.14in x2 (for two 2 inch pipes) =6.28in
Total area for two 2inch pipes=6.28in

A=R(1.25in)xR(1.25in)xPi=3.98in x2 =7.95in
Total Area for two 2.25(2 1/4in) pipes=7.95in

A=R(1.25in)xR(1.25in)xPi=4.9in x2=9.8in
Total area for two 2.5in pipes=9.8in

Now some large diameter Single pipe Calculations.

A=R(1.5)xR(1.5)xPi=7.06in
Total Area for one 3 inch pipe=7.06in

A=R(1.75)xR(1.75)xPi=9.62in
Area For one 3.5inch pipe=9.62inches

A=R(2)xR(2)xPi=12.57in
Area for one 4inch pipe= 12.57 inches

You could run a single 3.5 inch exhaust (pending it would fit) you would probly have to use some Turbo deisel mufflers, but i doubt they would fit under a fox.

Neat how two 2 inch pipes don't even come close to flowing what a single 4 inch will flow.

[MHISSTC]

I agree two 2 to 2 1/2" polished tips look better out the back than one big drain pipe.

I figured a comparison between the sound of a single vs. duals that both flow the same would be interesting.

I agree that a turbo will even out the exhaust pulses. I don't agree that duals always even out the exhaust pulses, unless the duals also incorporate an H-pipe or X-pipe crossover tube between the two pipes. In that case, if you're going to share the exhaust pulses between the two pipes, wouldn't it be the same as combining them into one pipe?

I also think you should qualify how a set of duals manage to flow exhaust better. Lets say at 5000 rpm your motor pumps out a volume of exhaust per second equal to V. V is equal to the speed of the exhaust (S) times the total cross sectional area (A) of the pipes. (V=SxA) This explains why the cross sectional area calculations were done above. If a singe exhaust has a cross sectional area of 1", it would have to flow exhaust at a speed that is twice as fast as if it had to flow it through two pipes that had a combined cross sectional area of 2". If the speed of the exhaust is halved, wouldn't the drag through the pipe drop to 1/4 of it's original value? (Any fluid dynamics specialists out there?) The engine also sees a lower backpressure that must be overcome by engine horsepower to push the exhaust through the pipe. So, even through the rate of flow through the dual exhaust example is only half of what it was, it allows the engine to work less to push the exhaust out (neglecting the effects of exhaust pulse timing and scavenging).

Also, if you were to take a single 2.5" pipe, spit it down the middle and weld in a 2" section between the two halves, making the cross section sort of oval shaped, it's cross section would be 9.9 square inches. This is essentially the same as 2.5" duals. I think a single oval tip out the back would look cool. 8)

Scott

[Anlushac11]

8)

two smaller diamater pipes can flow the same volume as a larger single pipe but the two smaller diamater pipes retain the velocity that the single large pipe would lose.

[Evil86lx]

I was pretty much counting on the fact that every aftermarket dual exhaust kit has some sort of cross over pipe... :D

kyle

[Mustang5L5]

I am running dual exhaust because

A.) the '88 came that way stock

b.) I had spare parts from the '88 so i am putting them on the '85

:)

[85CapriGS]

Why Dual Exhaust..... Simple it sounds so freaking SWEET!!!!! :D And that my friend is reason enough to go dual...

[bryant99]

Dual exhaust helps the engine to breath alot better than single exhaust

[OonDeanisS]

A=R(1.25in)xR(1.25in)xPi=3.98in x2 =7.95in
Total Area for two 2.25(2 1/4in) pipes=7.95in



that should say 1.125, not 1.25 to clarify.

[white1983GT]

hey imports have large single exhaust tips and they're cool right? They dont' even sound bad.
:roll:

interesting topic, but too much math for a hobby in my opinion

my exhaust sounds great, and i really don't care about much more than that.

[hemicuda]

I've heard stories of single exh. applications working as well as duals. However, it would have to be a large diameter and the number of bends and angles would also play into flow effect (no reduced diameters).

I'll tell you one thing, I've heard alot of stock full sized trucks and they sound pretty nice. Mellow, with just enough growl to turn your head. Then some guy puts on true dual set, and then all you hear is exhaust.

Reminds me of when people used to put cherry bombs on their vehicles.

My pace car had a nice growl to it with the factory single pipe, and got even better when I dropped the converter. However, the duals gave it a nice 'stereo' affect. I think that's what turns people on.