Exhaust flow on our V6s, the facts:

[LIZARDKING]

The attempted to get duals thread is getting way to long, time to put that one to bed.

I did some math and this is what I figure from the standpoint of how much will the exhaust flow in regards to the diameter of the pipe.

I assumed a couple givens:

The pipe will only flow as much as the smallest restriction
All sizes are in inches
Pipe wall thickness is .065
On the V6 muffler, the smallest restriction is the tailpipe at 2.25 OD/2.185 ID
On the V8 muffler, the smallest restriction is the tailpipe at 2.50 OD/2.435 ID
On the V6 duals, no mandrel bends the smallest restriction 2.25 OD
On the V6 duals, mandrel bends the smallest restriction 2.50 OD
The area of a circle is 3.14 x R x R

The size of the tailpipes may be slightly off, but the comparision is between each system, so the error, if any will be uniform between each system.

Stock V6 system ..........................................pipe area 3.5 ID
Stock V6 w/V8 muffler ...................................pipe area 4.5 ID
V6 split into 2.5 true duals no mandrel bends ......pipe area 7.1 ID
V6 split into 2.5 true duals mandrel bends ..........pipe area 8.8 ID

Granted, this doesnt take into account restriction caused by the mufflers, or the number and location of the pipe bends, but its a pretty good indicator of what the systems ability to flow is. Any of these exhaust mods will outflow the stock system, I didnt figure the split y-pipe, because Im not sure what the smallest restriction in that system is.

When considering if you want to make your own system or buy a prefab from the aftermarket, I think you need to consider what your long term plans are.

If you want just an improved sound then a V8 muffler or an axel back is the way to go.

If you want the look/sound of duals at a modest cost, have an exhaust shop do the work.

If you want maximum performance, go with a mandrel bend system, its more costly, but is also the best flowing system, hands down.

 

[05V6inMD]

But is the greatest potential for unsrestricted flow the best for performance?

 

[MCMustangMan]

I might be wrong (sometimes I am ) but isn't the exhaust pipe on the '05 V6 2.5" and not 2.25"??? When I went to put the GT muffler on mine (which I thot was 2.5") it fit right on the exhaust pipe. Unless you are talking about the muffler tips???

 

[LIZARDKING]

I compared the V6 and V8 mufflers side by side. It appears that hte inlet size is the same on both, but the outlet on the V6 is about 1/4 - 3/8 in smaller than the V8.

And yes, if you are going to have a 2.25 in bottleneck in an otherwise 2.50 in system, then the entire system may as well be 2.25 in.

We all dont share the same goal in modifing our exhausts. I want maximum performance at the lowest possible noise increase. I had an American Thunder system with a CAI on my 88 GT. When I fired it off at 5:30 every morning my neighbors wanted to burn crosses in my front yard. When I nailed the throttle, every cop for a mile around heard it.

I like the sleeper look.

 

[MCMustangMan]

"On the V6 duals, no mandrel bends the smallest restriction 2.25 OD"


I don't mean to be argumentative twofocused, but most people who are going to go the route of duals will most likely upgrade and purchase "GT takeoffs" or magnaflow, flowmaster mufflers, etc. that have the larger OD as opposed to buying another V6 muffler for the driver's side at 2.25 OD. I do appreciate the info though as it is very informative and without people like you crunching the figures, people like me are left with less than adequate information regarding our rides.

 

[351CJ]

of the pipe.

I assumed a couple givens:

The pipe will only flow as much as the smallest restriction

Don't confuse flow of a gas (which is compressible) through a pipe with flow of a liquid (which is not compressible) through a pipe.

It is not only the size of the restriction but the length of the restriction.

That is if you made a 1" dia. restrictor that is .010" thick and placed it in the middle of a 10" dia pipe, you can flow a lot more air through it than if you attached a 1" pipe that was 300' long. This is due to friction along the inside wall of the tube as the fluid (gas or liquid) flows through the pipe.

of the pipe.
Granted, this doesnt take into account restriction caused by the mufflers,

The muffler(s) itself is important as there can be huge differences it their restrictions from one muffler to the next.

Just going from a single muffler to a reverse Y with 2 mufflers will more than double the air flow. It gets a bit complicated, but if you double the size of the pipe, given the same input air pressure you will more than double the air flow. This is because flow vs. input pressure is NOT a linear function.

 

[GNN60GT500]

Don't confuse flow of a gas (which is compressible) through a pipe with flow of a liquid (which is not compressible) through a pipe.

It is not only the size of the restriction but the length of the restriction.

That is if you made a 1" dia. restrictor that is .010" thick and placed it in the middle of a 10" dia pipe, you can flow a lot more air through it than if you attached a 1" pipe that was 300' long. This is due to friction along the inside wall of the tube as the fluid (gas or liquid) flows through the pipe.



The muffler(s) itself is important as there can be huge differences it their restrictions from one muffler to the next.

Just going from a single muffler to a reverse Y with 2 mufflers will more than double the air flow. It gets a bit complicated, but if you double the size of the pipe, given the same input air pressure you will more than double the air flow. This is because flow vs. input pressure is NOT a linear function.

351CJ= correct.

Unfortunately there are way too many variables to try and calculate it on paper.

What Magnaflow has found on a stock or close to stock car-

Axle Back or Y pipe into Duals- these are best-

 

[LIZARDKING]

Remember that an engine is just a fancy airpump. The faster you pump out, the faster you can pump in. By creating restrictions in the exhaust system you are reducing the efficency of the airpump. And yes, air can be compressed, but that also creates heat, which is wasted energy.

The whole point of my post is to point out that the V6 can achieve exhaust system gains on various levels and prices.

Im going with a V8 X-pipe and a V8 takeoff catback on my V6, I think it will flow as well or better than any aftermarket exhaust currently on the market.

 

[351CJ]

Remember that an engine is just a fancy airpump. The faster you pump out, the faster you can pump in. By creating restrictions in the exhaust system you are reducing the efficency of the airpump. And yes, air can be compressed, but that also creates heat, which is wasted energy.

The whole point of my post is to point out that the V6 can achieve exhaust system gains on various levels and prices.

Im going with a V8 X-pipe and a V8 takeoff catback on my V6, I think it will flow as well or better than any aftermarket exhaust currently on the market.

Yes, it is true that an internal combustion engine is essentually an air pump.
And, the flow capability of the exhuast system depends upon the engine displacement and maximum RPM. Given the V6's smaller displacement and lower max RPM you only need about 3/4 the air flow capability that the GT needs.

One of the points of my last post was that the diameter of a restriction can be less important than the length of the restriction.

That is a 2.5" pipe that is 20' long may flow less air than a 20' long 3" pipe that has a thin (.010" thick ) 2" diameter restriction in the middle of it

Specifially, regarding your original post, the 2.25" tail pipe off the back of the V6 muffer is not the limiting factor in the stock V6 exhast system air flow because it is so short.

I am not a fluid dynamic engineer, but in a past life I did work with a couple of them so I do have a basic understanding of how fluid flow works.

 

[Philstang]

I have heard the the size of pipe aft muffler can be smaller because the exhaust gases are cooled/slowed down in the muffler...

 

[pwrhws]

That is true, the dia become less of an issue further from the motor.

 

[fazm83]

hey mike, any news/info/pricing on upcomin v6 turbo? That thing has me extremely excited.

 

[LIZARDKING]

I think you guys are overthinking my point here. Yes its true that fliud dynamics are very complicated and not easy to explain or figure out here.

Look at it this way: Take two 10ft long pipes with a 2.5in inside diameter. Leave one pipe as is, the other pipe bend and twist in several places and make a couple restrictions that are 2.25in dia.

Which pipe will flow better?

Back to my orginal point: Not all duals render the same results. If you want the look and sound of duals then the size and diameter of the pipe isnt that critical. If you want maximum performance then size, diameter, and restrictions are very critical.

Alot of guys who visit these froums are noobs to the hobby, Im just trying to help.