Looks like the FVD X-pipe is designed to flow similarly to Fabspeed's X-pipe:

 

Hint to A.W.E, probably this is the reason for the loss in power.

 

The FVD is definitely not "merging" as much as our design, but I also would not consider theirs to be an X-pipe. An X-pipe crosses streams much more than the possible merge they may have. In fact, there is a possibility that their two banks may not be crossing over at all and that is just filler weld between the two banks to make the part easier to build and install (I do not know how they market it). If indeed their two banks are open to each other where they meet, theirs is more of an H-pipe in the sense that there is lateral balancing vs cross-stream balancing.

Go back to the Fabspeed pic and trace the radius of their tubing to unveil what is behind the welded on nameplate and you will see that their banks merge almost as much as ours do, maybe a couple degrees less.

We modeled our X to promote as much of a venturi effect as possible since uneven firing balancing effect was not needed with the Porsche engine.

Like I said above, I think this would be a great thread for the actual companies to get involved in and state the theory and engineering behind their designs.

Here is another X-pipe design for the 997.2:

http://www.cargraphic.de/stepone/dat...1789c-2_gr.jpg

Cargraphic seems to be offering the same as us. An actual X-pipe marketed as a quieter "sound" version and a non-crossing rear muffler delete marketed as a performance version. If I have that wrong, perhaps Greg from RSS can chime in here.

Look, I realize our statements are controversial here. Heck, my rep points have been knocked down because some forum members don't seem to like what I am saying. But we're not here to present altered or fictional data in order to tear down the competition. To do so would ultimately hurt our rep as a company and would be disrespectful to forum readers. We could have opted to keep this data to ourselves, but we feel that our clients deserve to make an educated decision.

 

No, I am not confused. There are 2 issues:

1. from what side do the gases exit. In the 1st gen, the gases from the right bank of cylinders exited the left side of the car (hence the loosely used term crossover). In the 2nd gen the gases from the right bank exit the right side of the car through the use of the center muffler

2. what are the different ways in which the center muffler can operate
a. OEM - gases come in, make a u turn, then go out
b. Sharkwerks - gases come in then head out the opposite direction, just like first gen
c. AWE/Fabspeed - gases come in then collide in the middle (as the X section is open), then head out the opposite direction

So, my questions remain:
1. Why didn't Porsche have the center muffler go straight through rather than a U turn. What is the purpose of the U turn in the center muffler?
2. Why did AWE/Fabspeed have the x pipe open in the middle. Collision of gases does not seem efficient for sound or flow.
3. If you have an x pipe, why not have it closed in the middle yet retain the same characteristics of OEM in that the gases come in the x pipe then make a u turn (without colliding with the other side) then go to the same side of the car.
4. In AWE's full exhaust, they are moving the headers and cats further from the engine and using a method similar to the first gen and completely ignoring the the center muffler. I would think this would throw engine lights all over the place as the ECU was specifically designed to understand that the cats are close to the engine with dual chambers to heat up quickly. What is the solution?

Ok, that's enough for now. Time to go to work for my real job.

 

Mass you are confusing the cross over pipes and X pipes it seems.

A crossover pipe is 2 totally seperate pipes. The X pipe is open to both sides of exhaust flow at the cross of the X. The X pipe ties both cylinder banks together since it is open. The theory behind a X pipe is that since both cylinder banks are tied together there will be a verturi effect at the open part of the X and help suck exhaust gases through the system.

The X Pipe is proven and works on Vette's, Mustangs and so forth. The Porsche in the Koni series run by BMG racing uses a Fabspeed X pipe so I would think the X pipe also works on a Porsche even though the firing order is even unlike a american V8.

I hope this helps.

 

Todd I do respect A.W.E's honesty, and I'm more encouraged to buy from a honest vendor rather than a skeptical one, and It's clear that you guys have the X design 100% accurate, which will be great for a V8, all I'm pointing out is that I don't think that a traditional x-pipe is efficient on these cars, power wise that is..

Looks like Cargraphic's x-pipe won't unleash any extra power either, or they would've mentioned it atleast. Its just a matter of taste, some people prefer the sound, some want power, while others are looking for a balanced setup

 

Not quite.

A crossover pipe is exactly what is sounds like, the gases CROSSOVER from one side to the other. How the pipes are designed to enable that CROSSOVER of gases is a separate issue and can be achieved several different ways. Furthermore, a X pipe is merely the shape of the one of the methods to CROSSOVER the gases. An X pipe can be open or closed.

 

I asked this question too in a previous post and have not seen an answer or proof. I did ask a dealer/Porsche mechanic who is mod friendly and into tracking cars and so forth and I was told not to mess with the cats on a 09 yet...there will be codes thrown and so forth. The car will not think the cat is warm because it has been moved further away from the headers and the fuel amp will not be correct and the car could not run correctly. Until someone comes out with a ECU flash for a system that uses a smaller cat and moves it away from the exit of the header I would NOT buy anything. He said he has not seen a aftermarket cat that can stand up to the heat of racing or serious track days.

 

Agree completely.

 

I don't think that he is confused, he is just comparing 997.1 and 997.2 exhaust setup differences.

He does mention that the banks are open to each other.

 

Mass...a X pipe is NOT CLOSED, CAN'T BE CLOSED and call a X pipe or even a H Pipe...an X pipe is open at the cross of the X to both sides of the exhaust banks, always has been since these things came out 30 some odd years or more ago. If you close up the X PIPE, it would act like the crossover pipes you see Sharkwerks selling....their crossover pipes DO NOT merge the exhaust flow.

Exhaust flow exiting on the right or left side of the car makes no difference. obviously for flow you want a more stright through design but I do not in some aplications of exhaust tubing there has been some altercations to the flow to control power in certain parts of the power band. I read about htis years ago in Circel Track magazine.

I can't explain this anyfurther....I hope you can understand...I gotta hit the road for work. Talk later tonight.

 

Of course this is a major parameter that we are monitoring with this mod, but we are not terribly afraid there will be issues. We have already done similar mods on VW and Audi late model applications, as well as the 997 GT3, and have not seen any long term issues.

It is a valid concern, but easily monitored via scan tool to see if there is a problem or not. So far, we have not seen an issue, but we have not completed our full range of testing yet, either. We will only release this mod if there are no CEL issues discovered during our testing. If we can't keep off the CEL, that would also effectively kill our header offering, too, which would be a disappointment, but these are the steps that must be taken during prototyping.

 

Fabspeed is not not here to present altered or fictional data either!

Why one X Pipe design works when another fails?
by Kenny McNeil- Fabspeed Motorsport Managing Director Of Product Development

As seen in our video demonstration, a pulse of air (imitating an exhaust pulse) sent through the tube creates a vacuum resulting in a scavenge effect.

It is easier to see in a single tube but it works in intersecting tubes as well. The purpose of this design is to take advantage of the lost energy created by each exhaust pulse. Exhaust pulses happen once per firing cycle- per cylinder of any engine, so regardless if it’s an even or odd firing engine, as long as there are 2 or more cylinder. Pulses from one cylinder will aid in the scavenging of the opposing cylinder.

This happens because of the low pressure created when the velocity of the pulse or air movement travels across of the open area of the opposing tube.

As seen in our demonstration video when the air is sent through one angle of the X pipe and the tissue is swept through the opposing tube. By using this design in our exhaust the efficiency is high because when you use wasted energy to enhance the air movement of the opposing cylinders of the engine, it takes less energy to push the exhaust out of the engine, therefore saved energy results in more horsepower.

Another benefit achieved through the scavenging results in a cleaner combustion chamber which enables the fuel air mixture to burn more efficiently (again creating more horsepower and torque).

Because of space limitations on rear engine cars, it’s difficult to take full advantage of a true X pipe design. So we use a design constructed of 2 U-Bends. As seen in our video demonstration, when air passes through a U bend it has the same scavenging affect. Although it is not as strong as the typical X pipe, the slight intersections of the two U bends create an effective scavenging on each other. You can see how the tissue is drawn through the bend when a pulse of air is directed in the opposing bend.

Knowing how much of an intersection to create between the two U-Bends is the key to its efficiency. If there is too little area shared the scavenging result will be less. If it is too much of an intersection or the angles of the intersection are to abrupt done the air from one bank runs directly into the opposing bank and slows movement efficiency and lessens horsepower. Also note if too much intersection is used you reduce the total volumetric area of the system. This creates restriction resulting in even more Horsepower loss.

Understanding the dynamics of air movement and utilizing proven theories when we design our systems results in a quality system that greatly increase the horsepower in your car.


Fabspeed Video Explanation
http://www.vimeo.com/3110834

 

Hi Jeremy,

Your video inspired me to shoot a quick one of our own. As you can see, our X-pipe displays the same effect as yours. However, we didn't record the same power results as you did.

Have a look:

http://www.awe-tuning.com/media/mult...xpipe_demo.wmv

I don't disagree that you can "force" this effect to work somewhat with an X-pipe configuration like that on the bench, but when actually tested on the car, the power results are not what they "should be" because of the reasons I stated earlier in this thread.

Thoughts?

 

I am not an exhaust expert but an Aero grad with a basic understanding of fluid dynamics.

From the outside looking in, it looks like a slight change can make huge difference in power; one being greater one being less.

Looking at the Fabspeed design, it appears it would share pulses rather than collide one side into the other. The AWE is a more abrupt angle and would cause the two sides to mix and collide. As AWE stated and H pipe rather than an X pipe.

Why not test both on the same car and look for the best alternative?