In no way am I an expert...but your comments go again what I've read many times on this forum in the past...and it goes against the basic principle of needing some back pressure (from at least one functional muffler) to create torque.

I really don't care what exhaust people use (or like the sound of the best), have fun and enjoy your mods. BUT, I will say removing either does have a dramatic effect on the end result. The two bypasses each sound very different.

G pipe cars have a woof, woof Subaru-type sound. Sounds awesome, but a very different air cooled Porsche sound. The primary bypass, also has a deeper sound but still keeps lots of the other air cooled sounds in the mix. I only say this because I've read some people have been disappointed with the G-pipe sound...in that it really changes the nature of the engine note (much louder than a primary; Harley type sound; Subaru sound). Primary bypasses have their negatives too (it still changes the basic sound of the car, much deeper than stock; for some it's not loud enough). Not trying to be negative, just a heads up for anyone on the fence about which to choose...

I just had a shop cut out the primary and replace it with a straight tube...cost $50: https://rennlist.com/forums/showthre...ferrerid=19642


90 C2
-drilled airbox
-primary bypass
-Wevo motor mounts (I believe they change the sound... at least in the cabin!)

http://www.youtube.com/watch?v=GpqJm7lpzx8

 

Didnt notice any decrease at all. And the sound it makes in the mid range was sweet. But at idle and in the upper rpm range wasnt pleasent at all. If I could get this thing to sound like a 996 or 997 Cup race car I will be one happy camper....

 

[QUOTE=911Jetta;7850611]In no way am I an expert...but your comments go again what I've read many times on this forum in the past...and it goes against the basic principle of needing some back pressure (from at least one functional muffler) to create torque.


Hearsay is a funny thing. I have many days on a dyno with a NA 964. The dyno is more accurate than seat of the pants anyday. I'm an advid racer these last 15 years with a vested interested in actual numbers. Ask Geoffery Ring. He is an expert

 

[QUOTE=fstockcarrera;7852577]Right on Bob!!! +964

 

Quick question: for someone who's exhaust is still stock, where should I begin? In what order?
C2/C4 bypass pipe first?
G pipe first?

thanks,
ketel

 

If you want GT3 sounds I think headers are the way to go. Magnaflow mufflers on track create a unique whining that sounds un-Porsche to me. I've heard the G-pipe with Primary & Cat delete and it sounds too close to a Suburu for my taste.
Best sound I've found besides headers for me: Test pipe (cat delete), primary bypass pipe (cup pipe IIRC). The sound is grand upon WOT (wide open throttle) while low idle has a nice muscular grunt and sounds a bit like a truck...

 

My exhaust started stock and still run stock headers. So if it was me for my street car with stock headers. 1st and easiest Cup car air box mod...Some modest hp on the dyno and sound. 2nd Cat bypass, More Hp and Sound, Fabspeeds is what I have. 3rd primary bypass more Hp and More sound and still be able to pass sound on track days at those restrictive tracks like lime Rock. Keep the secondary "suit case muffler" as you lose only minimal HP to open pipes. I doubt that any of these mods HP gains are significant on the street. Don't bother with changing out the stock headers as they are actually not bad. This is based on SCIENCE not hearsay. Still IMHO

After reading hearsay positive and negative for these mods I spent Thousands to find out for myself. 20 Hp+ means something on the track, I doubt it is noticable on the street. Enjoy!

Bob

 

I have 100 cell CAT (Maxspeed canada), Danske Primary Bypass, Stock rear muffler and Maxspeed larger exhaust tip. In conjunction with my camshafts, the noise is epic AND it is beautiful at a cruise when you aren't giving it the berries.I have a soundclip which I don't know how to post on here but I could email it to you if you send me a PM.

What always amazes me is that the 964 / 993 / GT3 cars sound so amazingly different but the engines, inparticular 964/993 are so similar. I guess the biggest change is from the 964 headers into one single pipe whilst the 993 / GT3 run headers into a twin system. Perhaps a twin system set up with headers will give you the effect you are after and a good power gain as well I imagine. I personally think a De-cated 993 sounds the sexiest of the lot.

 

Yep

I got a good deal on the B&B setup (headers w/heat, no cat) and am here to tell you, I've never heard a better exhaust on a 964. At full chat it sounds like race car, but not too harsh, bassy, or loud. I wanted that killer flat six sound and I got it. Hard as heck to find clips of this setup though...I should do some filming.

The reaction from all my Porsche buddies has been wide-eyed amazement and kudos on the sound.

PS - there's a killer deal on this setup on Ebay right now (item 200512771522) - no affiliation - but a killer deal nonetheless.

 

Indeed, as there is no such thing as a basic principle of needing back pressure to create torque ;-)

 

This subject of exhaust system configuration and its effect on performance (not to mention sound) has got to be one of the most discussed topics on this forum. I have searched numerous hours over the past few years to find out more about the science behind all of this, and the best comment I can make is that very few of us (especially me) really know this subject adequately. The best and briefest non-emotional explanation of IC engine exhaust gas science I can find is at:

http://en.wikipedia.org/wiki/Manifold_(automotive)

If you read the section on exhaust scavenging you will see that "back pressure" is a byproduct, not a cause of power loss/gain. It's gas velocity that is of real importance. The level of science and technology needed to understand and tune exhaust systems is well beyond most of us, unless you happen to do it for a living as an engineer at a company like Porsche. Seems to me that many of us may actually stumble upon configurations that turn out to be improvements, as opposed to really knowing why, or we accept a reduction in performance in exchange for a desired exhaust note.

After trying a few different reconfigurations of my NA 964 exhaust based on recommendations from aftermarket suppliers, I gained a better appreciation for what the Porsche engineers designed. I lost about 10% of stock power in my first A/M setup, per matched dyno testing (not just my butt). Final version got me back to stock levels but with the sound I wanted. I have 100 cell cat + dual outlet primary (both Dansk) and kept stock secondary.

Really not trying to PO anyone. Hope the Wiki reference is of interest. Cheers.

 

Search no further, David Vizard has written THE best articles on exhaust science I have ever come across by a very large margin.

http://reocities.com/MotorCity/track/6992/vizard.html

This is David's 'original' article, just click pages 1 -10 (5 seems to be missing)

http://www.superchevy.com/technical/...xh/index1.html

This is a more recent edition, more difficult to read as the pictures/graphs are clustered together.

Happy reading!

 

Thanks, Evoderby. Very interesting! Now I realize I knew even less than I thought! Cheers.

 

Well I'm still not happy. Ran her with every combo. Then went out and purchased a stainless Magnaflow can and mod to fit by cutting the ends off of the old primary can. Sounds nice, fits great but still not happy. Starting to think that the 964 may not have enough compression for the sound I'm yearning for...

 

My guess is this is the noise you're after?

http://www.youtube.com/watch?v=8G19yu5xRxQ

I think there is a thread about it on this forum somewhere.