i saw the gentleman's post about the rennsport or the sharkwerx bypass...

a friend of mine has a 997.2 with the fabspeed.. which is like an X pipe in middle...


another friend of mine has the sharkworks one.. which keeps each side seperate..

they both have different side muffler setups so i cant compare them really. so im asking you guys.

would X pipe add more power? less? louder? quieter? resonate more? resonate less?

basically could you explain the main idea behind Xpipe.. pro's/con's?

i would prefer if the respective vendors would opt out in replying as their viewpoint could be construed as bias.

-alex

 

I have an x pipe installed on a 60's muscle car, and from what I understand, it evens out the pulse pressure of the different cylinder banks firing. Its supposed to smoothen out the flow and increase the velocity of the exhaust gasses. Because of an overlap between the end of the exhaust stroke and the beginning of the intake stroke it increases scavaging effects in the cylinder by the faster moving exhaust gasses, forcing more air and fuel to be pulled into the cylinder resulting in more power. The next time you watch a Winston Cup car flip over, look at the exhaust. Most of them run x-pipes. It will also change the exhaust note. My 60's muscle car has a very exotic sound to it when revved. Hope this helps.

 

wow thanx, better late than never

 

X-pipe makes things much better on V6 engines, it is an open topic if it makes things better or worse on flat 6 Porsche engine.
From my perception I do not see how it can possibly make anything worse, and it seems like in my case HP increase is there.

http://www.fabspeed.com/videos/Kenny...Air%20Demo.wmv

 

You have to have the crossover of the 2 cylinder banks at the optimum place to even out the pulses and help promote exhaust flow. You do this where the highest heat spot is. That is one way to tune a X or H pipe. Who knows if the X pipe on Porsche is in the correct place....it is in a covenant place for sure.

AWE tested this and claims a loss in power. Fabspeed tested this and claims a gain in power. Very contradicting results.

 

I think x-pipe effect by itself is hardly in 1/10th area of effect from changing stock cats to 200 or 100 cell sport ones.
x-pipe design by itself is somewhat like this ipd plenum - may be it helps, may be it does not. still it is a theoretically good design, so, who cares, plus it is not that expensive.

 

For a comprehensive thread on this topic, please see here:

https://www.6speedonline.com/forums/...ight=crossover

Also, we have more info as well as pictures and video on our site.

See here:

http://awe-tuning.com/pages/shared/p...fm&PPT=Exhaust


We knew this would be a hot topic of debate seeing that we found no gain with the X-pipe. However, we did our best to try and find some positive results. We just could not. It simply did not work for us.

However, the crossover pipes were a different story. They make the power, sound nice, and are cheaper!

Let me know if you have further questions.

 

Last thing I am interested is to participate in any brand wars, but you do realise that theoretically from gas flowing mechanics 'x' pipe and 'crossover' pipe is essentially exactly same principal design?

Practical implication here would be a ratio between residual pressure of exhaust gases from left bank in the exhaust system at the moment when right bank fires up - if you get gas from left bank flowing upward, toward right bank cylinders then you will get worse performance than with independent set of pipes - but essentially such thing may happen only with overly obstructive mufflers, so, as anything else, it is a system that has to be tested and tuned, not a single component, so any measurement related to single component here are pretty much meaningless.

From crossing exhaust pipes from different cylinder banks is a classic sport design and if done right in non-obstructive exhaust it should work as it simply cannot not to work. But, again, classic sport exhaust would not have cats and would not have mufflers - meaning it would be 100% non-obstructive flow with engine back pressure controlled by headers intake diameter only.

 

First of all, you are correct that no single component can be taken out of context. Any component’s worth is how it works with the *rest* of the system. So we can’t talk about x-pipe by themselves, we must talk about them in conjunction with the headers, cats, and mufflers. That’s why those benchtop compressed air videos are kind of worthless.

Second, x-pipe design originated with “odd firing “ engines. Odd firing means that instead of exhaust pulses alternating equally between the left and right banks of a V or flat engine configuration, there will be two pulses stacked back to back on the same bank. This back to back stacking causes a pressure increase in the exhaust, which the x-pipe is designed to relieve. It lets the pressure spike caused by these two pulses to escape to the other bank, which keeps velocity up, which helps cylinder scavenging. The concept works, and has been used by countless V8 tuners for years.

HOWEVER, the Porsche flat 6 is an even firing engine. It does not suffer from this exhaust pulse stacking handicap. Therefore, the use of the x-pipe is inappropriate here from a pulse pressure relief perspective. And not only is it the wrong use of a power concept, it actually HURTS power on the Porsche flat 6 in our extensive controlled testing. Check out our site for dyno sheets.

Do a forum search, and you’ll also see people reporting low end power losses when installing an x-pipe on their 997, which is what our dyno sheets show, too.

All this info is out there on the net, so please do not just take my word for it. This is not biased, this is scientific.

 

That may be true to some degree, but from other perspective efficiently a pre-muffler link between left and right pipes should reduce after-cats gas pressure as it allows gas to be more equally dispensed across both mufflers.

From flow dynamics alone theoretically that link will create additional turbulence but considering actual pressure at 3K rpm I do not think it should make any actual noticeable effect, anyway, who knows.

Only meaningful exhaust parameter affecting engine power is value of gas pressure at headers intake. Any residual pressure from downpath piping is essentially bad and has to be minimized. Looking at stock non-sport design I do not really see how any after-cats piping (unless it all gets physically stuck) will affect pressure at headers intake as cats by itself represent major bottleneck in the exhaust system and gas pressure difference before and after cats should theoretically be much bigger and efficiently minimize any subsequent effect from any changes in downpath piping to non-essential numbers considering we have pretty much free-flow mufflers.
But point is - compared to cats, even 200 cell ones, mufflers are essentially transparent to exhaust gas flow. And again, purely theoretically, any x-pipe design will not work and create obstruction only if we have constant equal pressure in both left and right pipes. If pressure is not constantly equal and I do not think it is a constant flow even with flat 6 Porsche engine - x-pipe link should be able to reduce pressure in non-active bank side and essentially help to reduce pressure before cats when engine fires up that cylinder bank.

So I am not even going to speculate how and why dyno sheets do show what they do. It would be interesting experiment to drop off mufflers altogether, keep x-pipe on, adjust ECU to this flow, run car on it, then put on classic non-linked cats with same exact brand of converter, adjust ECU to it and run it.

From practical perspective IMHO all that is pretty much non-meaning non-sense, as all this theory of flow dynamics will actually start working 100% only if we throw out cats and mufflers. I am positively sure at any rpm higher than 3K residual gas pressure before cats does not dissipate to the level to make any subsequent effect from after-cats piping to affect final result, but, who knows, may be I am wrong about it altogether.

 

Again, I do not care who is who here and I have no affiliation with anybody but myself - I look at those 2 designs below - from flow perspective alone in first I see 2 parallel streams connected by a connector pipe of much less diameter than master pipes and placed at 90 degree to a stream so this is non-obstructive and will create suction force from pipe with less pressure as stream path is not affected. In second picture you have 2 intercrossing streams affecting each other and creating turbulence and affecting steam path. Both designs go by 'x-pipe' name but are essentially very different.

Again, my pretty firm believe is, it should not be affecting pre-cats gas pressure by much anyway.

1)
http://fabspeed.com/997_24.html

2)
http://awe-tuning.com/media/products..._xpipe_800.jpg

 

great question man, I was always wondering the same thing...great info guys