danilonovelli

hi gang.... have had a few 911s and have always modified the exhaust system... on the 997.2 models I always replaced the center pipe with an aftermarket product - AWE, Fabspeed, Sharkwerks, BB... on the side mufflers I have tried PSE, FVD, Fabspeed and Gundo... I just cannot stop tinkering :-)

so, seeing how well the Gundo solution works on the side mufflers, I set out to focus on the center muffler and see what can be done with the OEM unit... got a used one from ebay and started cutting away... the unit internally is like an xpipe with 180 degrees bends on each side... but there is a section on each side that has a 3 inch perforated tube (see pics)... this does a lot of sound/volume damping/cancellation at low rpms which helps keep the car silent at low rpms... so exhaust goes through the perforations and fills up the whole box - as the internal separations are not sealed... once you accelerate and put pressure in the exhaust system, most of the sound/flow goes straight out due to velocity, though there is still damping.. and probably some backpressure due to low pressure created by the big box

so I covered the perforated pipes with a special exhaust wrap that hardens like steel with heat, hence eliminating the damping effect/low pressure at any rpm... other solution would be to cut out the perf pipes and weld solid ones in but too much work for the experiment... welded all back on, making sure the box is still sealed, though there is no need for a total seal anymore, ceramic painted the unit and installed on car... pics below

RESULTS: noticeable more sound/volume from low rpms - good one in my opinion, but that is subjective... sound volume is similar to aftermarket options, though they have invested in research and tested different combinations, like Fabspeed mixing flow from the 2 banks in the middle of their xpipe product, which is awesome... and Sharkwerks has eliminated the 180 degree bends allowing flow to be more direct... same as AWE and BB... all great products that fit as OEM and great to have so many options to chose from to really tune the sound to our liking

Summary (similar to Gundo benefits):

• Sound/volume increase
• No drone
• OEM look and fit
• Cost = cheap
• No CELs
• No weight loss - aftermarket options will reduce weight
• No performance gain - aftermarket options claim some
• Joy of working in my garage!!! Already working on a second unit for a friend

I am running it with Gundo exhausts on my 2009 997.2S and I love it!

So question is... what do we name this mod? I am Italian and Gundo sounds like Secondo - or second... so we should probably call this Primo - which is First, as in first muffler... makes sense? unless someone already has done this and got the copyright ;-)

Danilo

Mumbles

Interesting, but is that metal tape like metal duct tape you wrapped the baffler in ? the muffler heat should melt the adhesive that will make the tape fall off.

If it does hold up then good for you.

vern1

Why wouldnt you just get rid of the centre muffler? What am i missing?

danilonovelli

Lol u r missing the whole point which is tinkering in the garage, experimenting, learning, building or modifying something on your own, ... and why would i want to get rid of it?? To save 10 pounds? Like that will change my power to weight ratio for 0.000001%? This is not about saving money vern1... it is about using your brains and hands

@mumbles it is not just metal tape. As i mention in the post it is a specialty exhaust wrap. Under the exhaust metallic tape u see in the pics there is a mesh that turns into a metal-like material once it is heated. It is made especilaly for exhaust repairs

docdrs

Great mod but I would say its similar to fabspeed x pipe not gundo. I would just call it the Danilo Hack

danilonovelli

hey Docdrs... thanks for the feedback... I meant Gundo style as it is a mod/fabrication on OEM parts... so in the same spirit as Gundo... cheers

lowpue

Actually this was very useful for me. I was just having the discussion with someone on this. We were trying to figure out if the exhaust two sides actually intermix to see if we can use this for a custom set up. We shined a light down one end and could not see light at the other end so we assumed that it was not connected. I think your experiment shows otherwise. They do have a common cavity. Thanks for sharing. I learned something. :-)

docdrs

full cutaway view

danilonovelli

@lowpue... I have another unit coming in that I will open up again... let me know if you need to see anything in there or need more pics... cheers

vern1

Who said anything about money (except you who said it was cheap)? The only thing it seems to do according to your is a slight increase in sound. If that was the objective (and still not sure what the objective was) and if you were using your brain, you'd ditch it and that would produce a better sounding, freer flowing exhaust (and save weight )

Am all for tinkering but just don't see the purpose.

lowpue

So they are independent and not common...thanks for setting me straight.

318touring

I'm also wondering whether this mod alone is worth the effort vs buying bypass pipes.

danilonovelli

@lowpue... the divisions inside the box are not sealed (you can tell by the black soot on the edges and the fact that it is not welded all around those divisions)... so exhaust will spill inside the whole box... cheers

danilonovelli

@318touring... if all you are looking for is more volume then this could be an option... mind that the used can cost me $75 and to do the job I spent like$15... so $90 total... but of course this was just an experiment to figure out how much more sound it would produce, drone, ... just like Gundo hack, this would just affect sounds... if you are really looking tor perf gain then aftermarket is what works.. they have done proper research and testing to improve performance... cheers

Tj40

I can see the point if you are in a jurisdiction that has restrictions on aftermarket exhaust components and wanted the extra sound a x pipe would give you but you want the exhaust to look stock from the outside.

Then again given the number of threads where people complain about $700 or more for 2 pieces of steel tubing that constitutes an x pipe then doing this actually makes more sense, unless you want the weight loss.

​​​​​​And of you think the weight loss is significant remember you can have a bigger impact on the weight of the car and front rear distribution by just filling the tank up with gas!!