vespam5

I am trying to figure out which one to use. I am assuming that it is a little quieter to bypass the secondary pipe?

Thanks!

raspberryroadster

eitherone will contribute to engine "voice" (may be a debate on what's best)....but primary will give you biggest weight loss - not a bad thing
be interesting to conduct a poll (primary/vs 2ndary delete....i did primary, remain happy)

Racker79

Depends what you are after.
Primary (cup pipe) and secondary (g pipe) remove = weigh save and more noise.

primary replacement, apparently many people like the sound.

What I have read so far is that both do not reduce back pressure much so not much hp gain. So for Hp gain a cat bypass or a 100 cell cat would be the choice.

I have a cat bypass in my garage. I curious to see the sound and hp difference.

Racker79

BTW has anybody an opinion on to remove the primary and secondary and replace it with a new primary with two exhaust tips?

TAI2

I have tried these various combinations. They are listed from "quiet" to "loud".

1. Stock CAT, Primary and Secondary in place: Normal bark
2. Stock CAT, Primary Bypass and Secondary in Place: Nice bark and not too loud at all
3. Stock CAT, Primary in place and Secondary Bypass: This sounds really nice and will pass the noise test at Limerock.
4. Stock CAT, Magnaflow Primary and Secondary Bypass: A real attention grabber, great bark which people compliment but on the edge of being too loud for Limerock. This is my standard set-up.
5. Stock CAT and Primary and Secondary bypassed: Cup exhaust setup, sounds like a monster, you will need earlugs for any distance driving. Depends on your helmet but you probably need earplugs at the track.

I did hear a car with option 4 + a 100 cell CAT and it too sounds great and not much louder than my car.

Tom

Jim Howley

I currently have a cat bypass and primary bypass but I preferred the sound of the secondary bypass I had on my C2 so I will be changing over to this setup shortly.

springer3

I have the primary bypass, stock secondary and cat. I can sneak out of the sub-division without upsetting the neighbors, but it sounds great when you go full-throttle.

kdfwagen

from what I have read it sounds like the g pipe (secondary) has a good idle note (chevy rumble) while the primary has a nice howl when you get on the throttle.

Either way, I want to buy a used primary or secondary so let me know if you have one for sale!

911Jetta

-drilled airbox
-primary bypass
-Wevo motor mounts (I believe they change the sound... at least in the cabin!)

If you have friend who works at a muffler shop, try this:
Primary bypass - $50 muffler shop cup pipe

PNine64

I had a primary bypass and put the long g-pipe back on this weekend. It is loud but when you are hitting the upper RPMs it sounds like a freakin' race car. Already talked to the neighbors over a beer last Friday and apologized in advance.

eman123

I've got a primary bypass (cup pipe) on order from FVD.. Will hopefully get soon.

I have the stock cat and stock secondary. Hopefully I made the right choice.

vespam5

Great response guys thanks! I think the secondary bypass might be for me. Perhaps a 100 cell cat in the future since removing the cat completely is a stinky and un-green way to go....

Jimjacqmx5

I have a 100 cell CAT and primary bypass from max-speed in Canada. I also have their bad *** exhaust tip which actually made a BIG diffrence to the depth of the note.
Really nice note but doesn't drive you mad when you aren't up it.
My best mate lives in Califormnia and works for Top gear and EVO magazine and reckons it's the toughest sounding 911 he's heard if that counts for anything.

The big advantage for those tracking their car or after handling benefits is that the primary bypass removes the weight from the very rear centre of the car which is exactly what you want.
That said, a secondary bypass sounds sexy too.

I'm thinking I might bin the secondary muffler and just run a 100cell CAT.

More weight savings and super tough.

I only wonder whether this will actually result in a power drop as too little back pressure.

Any thoughts you engineering types out there....