Originally Posted by Iceter

I don't see how improving exhaust flow would decrease power. Bypassing the mufflers could only improve power.

Originally Posted by Dan@SharkWerks

I had a call about this earlier and wanted to address this topic. We also just installed one today (2009 PDK with no side muffler mods) and there are no vibrations on the car at idle or in Drive at a stop.

I don't know if it's due to what we changed with the design over the years (we now have added clearance for PSE side mufflers and completely changed the bracket system that attaches the muffler to the car), but I have not seen a 997.2 vibrate with our center exhaust for at least 4 years now. I believe that issue is 100% fixed. This was very early on with our first designs which may have not fit as nicely onto the header flange as well.

It was very rare anyway - I heard maybe 3-4 complaints over the years on these from customers and the parts were not installed here so I could not check clearances vs side mufflers, torque etc. to confirm, but we also never heard of this happening on cars with PSE or Gundo / FD hack.

Originally Posted by CTCOOP

Just did the Fister mufflers (1.75'') with fabspeed x pipe (6 speed Cab). It sounds GREAT (IMO) but I can't imagine wanting it even a little bit louder than it is currently. Although, I don't know that the 12% difference in diameter can truly be equated to a 12% increase in sound - I would think less of an increase. Going to need an engineer to weigh in on that one...

Anyways, sound is always personal preference, but my new setup is LOUD with the top down over 3K RPM. As in people turn to look across 3 lanes of traffic in town wondering what that sound is

Originally Posted by ElectricChair

Thanks for clarifying, Dan. Do you mind posting your return policy in case someone decide to go with your center bypass and get any issue?

Originally Posted by ElectricChair

This might be loud enough for me.

Under 3k RPM, would you like/mind to have it a bit louder?

Originally Posted by WantA997

Just curious why you went with Fabspeed over Sharkwerks (or even Billy Boat)?

Originally Posted by ElectricChair

A few posts/threads that helped with my decision:
https://rennlist.com/forums/997-foru...l#post10397993
https://rennlist.com/forums/parts-ma...l#post11475042
https://rennlist.com/forums/997-foru...l#post13073675
http://www.6speedonline.com/forums/9...er-bypass.html

Also a few rennlisters reported drone and vibrations with sharkwerks on 997.2 PDK cars (note = PDK cars only). Asking around before taking my decision, I got this PM from a fellow rennlist member:
"Just an FYI, I had a Shark works Cross pipe shipped and I installed it to my PDK car. I had to remove the cross pipe due to vibration at idle. ( I think it dropped my revs a little causing the vibration ) bad enough that the inside of the car, seats including were shaking."

Sharkwerks added a note to their product page:
http://www.sharkwerks.com/products.php?pid=193
Note: A small percentage of owners have reported that there is a slight vibration at idle speed in Drive (PDK models only), when the brake pedal is depressed at a stop. This has been reported with all aftermarket exhaust systems. This can be fixed with a software tuning upgrade. It is considered normal and will not harm the vehicle.

My understanding is that droning and vibrations can occur with any exhaust mod. But since I am doing a DIY project, I chose the "less risky" road.

Originally Posted by kruzn911

very interested in the same setup as you. Looking forward to hearing some sound clips!

Originally Posted by Crester

I have the set up you are going for... Fabspeed and Gundo. I went with 2" and I think you should as well. The car isn't that much louder when driving normally. It's only when you are heavy on the throttle that the car gets loud.

I also choose Fabspeed over Sharkwerks because of the vibration issue on PDK cars. I don't have any vibrations when stopped... but the Fabspeed makes your engine sound more high pitched. It's upto you if that's a good or bad thing.

Originally Posted by Ducati_John

The muffler is an acoustic low pass filter - it attenuates high frequencies coming out the engine via the exhaust pipe. When you do the gundo hack, you are partially short circuiting the acoustic lowpass of the muffler. This means more high frequencies get through. When I did my 2" hack, I got about 20dB more output between 150Hz and 600Hz. This changes the tonal characteristic of the exhaust sound. In my case, I heard a lot more crackles on deceleration and in general it sounds raspier. A smaller pipe would be less of a bypass and would tune things a bit differently. Without making a more detailed model, I couldn't say exactly what it would do, but generally I'd expect less increase of high frequencies compared to the 2" pipe. I took some measurements of my 2" hack with Sharkwerks bypass and posted them here:
https://rennlist.com/forums/997-foru...l#post13403188

Originally Posted by Dan@SharkWerks

We offer a 100% refund within 30 days including the shipping to/from Shark Werks for any products we make. We offer a replacement warranty within 3-years if any new issues come up. After that, email us and we'll see what we can do.

Originally Posted by ElectricChair

I am not an expert but as far as I know, too much flow without tuning may decrease power and/or torque. It's an interesting topic.