i have been looking at the different by-pass pipes for the 7GT3 and have some comments and questions.

though i have not opened the stock center section to have a look, it looks like the left and right side exhaust streams eventully meet in a shared chamber before exiting the tips, thus equlizing the back pressure of the left-right cylinder banks.

the after market units lack this chamber and some just connect a cross-over pipe connecting the 2 sides.

that cross over is positioned in such a way that pits the left-right exhaust streams on a head on colision with each other.

in a traditional front engine car, the left-right exhaust are flowing in tubes parrallel to each other and flowing in the same direction so you have h-pipe or x-pipe in place to equalize the exhaust pulse.

i have not seen to many independent dyno testing on these but it would seem like there is some interference going on back there? i could be all wrong on this so if someone would explain it, that would be great.

 

The only point the two sides meet on the stock system is at the tip outlet if you will. We tried a lot of different designs (all with varying degrees of sound/tone/performance/backpressure effects) a couple of years ago and settled on two independent sides that do not cross/meet. There is indeed that debate about crossovers on these engines (also muffles the sound somewhat) so we kept the banks separate. There were a bunch of dynos done not long after our release in 2007 by rennlister's in Canada and the US in different areas as well as other shops showing no loss in power etc.... We also used different dynos at Stasis for example (so that's independent too since they have nothing to gain). You can search/find them there but again to make any sort of power on these motors you really need to build them. Exhaust, software etc... will only get you a few ponies. If you're changing the exhaust I'd do so only for sound/weight reduction and not for HP. And I totally agree with you, even in stock form they sound pretty darned good to me:P

 

thanks Alex. so i guess thats just a brace connecting the 2 sides on your bypass. it did look kind of small for a proper h-pipe.

do you happen to have pics of the center section after you opened it?

im not really looking to make any power. i know its a high strung engine, i just want to make sure i dont lose power. for me it would mostly be for bolder sound and a few pounds of the rear.

if the factory indeed dosent deem an h-pipe essential, not sure why so many incorporate it into their by-pass design.

would like comment from RSS, GMG, and especially Cargraphic with their double stack design.

unless im told otherwise, seems the no h-pipe would produce no interference.

 

hey bara my pleasure and yes that's a structural brace and not a connecting pipe. I'll dig out some pics from the old HD but I believe they're still on RL And all the dynos (in canada, East Cost, EVO/AZ, Stasis etc...) showed no loss in power either. And seems like you're on the right track though- don't expect much other than some sound and weight-loss We used our center section for the 3.9 project fyi.

 

thanks Alex. not trying to start a product bashing here but rather for vendors to explain the benefits of their design.

heading over to RL for those threads

 

Hi Bara,

Good post as I'm sure many folks wonder the same...

Like Sharky and many enthusiasts, we love the GT3/GT3RS models with a passion, and they are pretty darn amazing right out of the box. We of course, like many on this forum, enjoy customizing and personalizing our vehicles.

First, with the Xpipe offered by RSS, as we state in our threads and sales material, we primarily wanted to address the "lack luster" look of the factory tailpipes and enhance sound – not to gain power. To each their own, but we would prefer something different visually. We already manufacture great looking tips to bolt on the factory or other great aftermarket bypass offerings, but we wanted to go one step further. We wanted an all in one unit that addressed sound, weight reduction (the Xpipe weighs only 8 lbs.), and offered with aggressive tips included. To top it off, make it available in satin black ceramic coat to suit our style. With this Xpipe bypass design, we feel it meets all our base criteria.

In regards to the Cargraphic (w/ RS Tuning) bypass design – weight reduction , sound and looks were the driving forces as well. I will translate some of this German and post up their information/perspective on the bypass offerings as well.

Simply put, the GT3 series are bad ***. For those looking to personalize a bit - there are great choices for enthusiasts by all the top tuners which I think is very cool. That way everyone doesn't run the same thing and have a variety of exceptional products to choose from.

We'll post up the Cargraphic philosophy shortly....

Most importantly - congrats on your GT3!

Bryan

 

GMG was one of the first companies to offer a secondary muffler replacement when the 997 GT3 was introduced in early 2007. After testing and working with the engine builders at PMNA we came up with our World Challenge Sport Center section design which incorporates two megaphones with an equalizing chamber. The two megaphones speed up exhaust flow while the balance chamber equalizes the exhaust pulse and provides enough back pressure so the engine does not loose power. The balance chamber also improves the sound of the exhaust note and minimizes drone in the cabin.

For the 2010 GT3 and RS our WC Sport Center Section is very close in design but we have taken the added performance of the 3.8 engine and made subtle changes to the system.

We have clients throughout the world who have installed and been very happy with our product - A simple YouTube video search will results in dozens of video's on and off the track.

For more info the system along with video's and sound clips please visit our website.

http://www.gmgracing.com/porsche_exhaust_gmg_wc997gt3.shtml

We also offer our system in Ti which weighs in at 2.8lbs a nice upgrade for those who want the utlimate in weight savings.










http://www.youtube.com/watch?v=Et__c...layer_embedded



We are also running a holiday special on our World Challenge Sport Center Sections for the 997.1 GT3/RS and the new 2010 GT3 and RS as well.

Please email me directly for special pricing.

 

Hi Bara,

Here is some insight into the RSS X-Pipe Design Philosophy.

The X-Pipe Theory,

For any performance exhaust system, some type of crossover connecting the two sides of a dual exhaust system is important because it acts to balance the two banks of the engine. The common H-style crossover is good at balancing sound pulses between the two halves, but does little to promote scavenging because the exhaust gases tend to follow the path of least resistance, which is straight through each pipe rather than taking the 90-degree turn through the H-pipe into the other half of the system. In an X-pipe system, however, where the two sides of the system intersect, the gasses have no choice but to intermingle as they pass through the junction. This promotes improved scavenging effects by smoothing out uneven exhaust pulses from the engines firing order. According to the theory, the faster acceleration of the gasses through an X-pipe causes them to flow in a linear fashion parallel to the walls of the tubing rather than tumbling. This “laminar flowing gas” is much quieter than tumbling gas, resulting in better scavenging and a unique exhaust tone that traditional H-pipe style cross over or individual non crossover exhausts do not offer.

As Bryan stated earlier, RSS wanted an all in one solution for the GT3 that addressed sound, weight reduction (the X-pipe weighs only 8 lbs.), and offered with aggressive tips included. To top it off, make it available in satin black ceramic coat to suit our style. With the RSS X-Pipe bypass design, we feel it addressed all our base criteria. Most importantly our customers have validated our design goals based on their positive product feedback thus far.











Happy Holidays,

RSSmike

 

How do all these effect exhaust back pressure? Dealership indicates these will cause premature RMS issues in 07/08 GT3 due to inconsistant backpressure issues....
Is this Bull Poop? What is the reality?
thanks from a newby waiting on his GT3 to be delivered next week.....

 

Now thats pretty interesting.. The dealer to tell you the RMS leak will be premature is BULL POOP IMO.. So they admit the RMS leak is a guaranteed issue and itll be even sooner due to less back pressure.. Sounds like they are prepping you for denial of RMS warranty when you come back exhaust on it..

Mike

 

Your dealer is confusing exhaust backpressure which helps evacuate the cylinder and keep velocity up with crankcase backpressure which occurs when your rings are worn etc., and combustion pressure leaks to the other side and can cause seals like the RMS to leak. If your exhaust BP is effecting pressure at your RMS you have bigger issues than a seal.

 

thanks for the feedback Mike. No the dealer only indicates that RMS leakage is normal only on GT3's that do not get driven much and that a service bulletin indicates this: RMS seal is a vacuum seal opposed to a normal seal like on TTs and 997s - and they are good for 5hp..(I am not worried about them covering a leak for warranty - car has CPO) But I do believe they are not supporters of aftermkt goodies...I saw this with my 996 with "EVOMS...the cause of failing MAF sensors" etc....and you are right they will probably use the new pipes as reason not to cover something.....

 

thanks Dave - you are probably dead on with this.