I just weld as a hobby and sure don't do it for a living but I thought he did a great job and the welds look good to me!

 

Would it be possible to just remove the secondary cats and hollow them out? Thats free-

 

The short answer is yes. Lots of work but possible. I did this on my Audi S4 and Yamaha R1.

 

Yes, but some people claim that by removing the innards you will create turbulance when the exhaust flows through and actually decrease HP more blah blah blah........

 

Interesting thread and even more interesting comments. Hats off to those with the creativity and willingness to try something and having the confidence and conviction to put it out there for us to see.

I consider exhaust systems as mostly functional although I do like nice looking tips,and systems that do not overwhelm me with sound.

Choices for mods boil down to mainly one area...

Requirements: What we want something to do and how we want it to do it...examples:

functionality, longevity, aesthetics, cost, materials, etc

Each of us have to choose what our requirements are and they are different for everyone.

How can we criticize someone by imposing our own requirements over theirs? I for one will not open my wallet to the tune of 500 or 600 dollars for a bypass especially when 500 or 600 can get a complete system on any other car...ridiculous! Maybe I just do not have an excessive bank roll like some. Even with an beautiful or ugly setup is installed, I will never be underneath....nor will my passengers. I never park over mirrors and my car will never visit barret jackson with their chassis cam!!!! How many of you are going to ask people to crawl under and look at that artful piece? LOL

My requirements are simply functional and 500-600 dollars spent toward an aesthetic look is a waste of my money (notice how I said a wast of MY money).

Bottom line...I am not sure we have any business being critical of others work. Enough said.

Now, how can we re-produce that home built bypass on a larger scale? I am willing to pay 150-300 for a bypass! How come the commercial companies do not have two versions of their bypasses...one for go, and the other for show and go and price accordingly?

 

HAHA I agree with you 100000000%!!! I contacted Sharkwerks about this issue asking whey they cant just outsource to China and have them mass produce these pipes since they are so popular and they said:

"I wish I could too... I understand where you're coming from and part of the reason for even doing them was out frustration that the $600 ones didn't have hangers like the factory ones. There's actually however quite a bit more too it than you're assuming... it might well seem like just two pipes but there's actually a good bit more to it than that. There's other costs such as prototyping, flanges, welding, mandrel bending, equipment, new hardware, gaskets, shipping supplies, testing etc... Nobody sells the exact pipes you need... The two pipes aren't the same either. I can promise you that if you did go to a place and try to make your own you'd be surprised at how much it actually ends up being. We're not exactly making a significant margin or anything. The main reason was indeed to have hangers which you'll see are on the stock ones that you remove. They're very much integral to holding the entire exhaust in place. For sure if you do have the time take yours off and see how much it'd be because I'm guessing you'll be surprised . You might actually find it cheaper/easier to gut your secondary cats if you wan to try something like that."

YEAH YEAH YEAH.......Give me a break, its a short section of pipe that any experienced welder could fab up. I might just have an exhaust manufacturer in China make me my own version and then I will sell it to everyone here that is tired of being scammed by these companies!! How does that sound?

 

Actually, this is a fact... its detrimental to the airflow. From the Exhaust port to the exhaust tip; airflow is a matter of scavenge vs flow rate vs flow speed.
Hollowing them out isn't a good idea... besides, its actually more of a pain -

That secondary Cat is superfluous as far as being 'green' goes. Most Mfg put the 'other' Cat up near the headers so it heats up faster, thus gives them that coveted ULEV rating. After 2 minutes, that first Cat does '0'.
However, on Cayenne's, its to remove that 'ratty' sound you get at WOT.

Again, personal preference...

Me ? I'm leaving it & doing FastHackem's Muffler-Pipe-ByPass Mod.

 

Hey anyone in California and know if the Bypass pipes will still allow you to pass Smog?

If not then hollowing out your cats would be the best option because the look of cats will still be there but you can get the modest power bump and sound.

My buddy has a Turbo and is a cheap Bast*rd!

 

The big question, is it more detrimental to the total flow than the cat itself on the Cayenne?

I know for a fact that on the Audi S4 and the Yamaha R1 that gutted cats produced power and throttle response gains. Just go read any of those forums and look at the dyno charts as proof. I know there are other cars/bikes out there that have the same result.


It would be really easy to just cut these cats in half, remove the insides and weld back together. Just pointing out that it is simpler and cheaper than having a pipe bent to weld in it's place.