kusee pee

Quick questions for all you noise-lovers: I'm running a g-pipe and love the noise. But naturally I'd love even more. Which would make the most noticeable improvement to my current noise, a primary bypass or a cat bypass? Or would neither add much? I'm paticularly keen on any closed-throttle popping and banging I can get...

I'm in that lovely position of knowing that I'm about to shell out for service, discs and pads so need to soften the financial blow...by spending some more

964rh

I believe a cat bypass would add a bit more noise, primary as well as g pipe wouldn't give you much back pressure so you may lose some power if you bypass both silencers.
I used to have a cat bypass and g pipe and loved the burble it gave but it was too loud for tracks in the uk. Measured 108db at a track day at 3500 rpm. Cat and primary bypass with sec. silencer give a raspy sound and mine measures 105db currently.
I've heard the ghl systems make it seriuosly loud but have never heard one. they are expensive tho' so you'd get your wish of spending more!

Rob

TR6

I have the secondary bypass and cat bypass with the primary silencer still present. Like you, I started out with the secondary bypass and stock cat and primary, and then later added the cat bypass. The Cat bypass added a little more noise level and a little more "popping" and "burbling" on deceleration, but it didn't dramatically raise the noise level as I would have expected. And like you, I don't mind the louder sound and the noise level. I have no idea what additional power, if any, that it may have added, but it did reduce the weight somewhat. Those original components are heavy.

doug751

I used a fulll Fabspeed system to eliminate the CAT and the Seconday and replaced the Primary. The sound was fun for a few days, a bit more like a Harley or an old Muscle Car. However, I could no longer hear the fan or the other engine noises and so the car seemed less "Porsche" like. I did not notice that much of a difference power wise, perhaps a bit on the top end but that could be just the noise.

I used the Fabspeed airbox kit for a few days and it was fun but got annoying. I did use it on the track until I crashed the car, because it gave an audible feedback for the throttle position that was helpful for track driving.

Also, I did not like the raw gas smell in my garage or on my clothing from CAT being removed.

I wrecked that car, bought another 964 and plan to leave it stock for a while.

Chris M.

Bypassing the primary and secondary will be VERY loud, way too loud for the street. To add just a touch more noise go for the cat bypass.

Chris 911

I tried first the primary bypass (Cup-pipe), with cat and secondary still in place. A little increase in sound, not so much in engine power, little bit on the top end perhaps. After a run on the Autobahn in Germany the secondary muffler split on the outer coating, so I ordered the G-pipe (secondary bypass.)

Just to check it out I tried bypassing the primary and secondary muffler, with the Cat still in place. According to a video on Fabspeeds website this was the setup for the 964 Cup cars, but cannot verify this. It felt like the car had much more power, especially in the top, but this could also have been because of the shedding of weight of the car (nearly 40kgs in total) This setup was LOUD, and not something to live with. Fun to give it a try, but as my car was a daily driver, I could not have this setup. Sounded a lot like a Chris-Craft boat on idle.

I installed the G-pipe. and that had a different sound of the Cup-pipe, a bit deeper sound, and a little louder than the Cup-pipe. Seemed to give a little more low end torque, but not much more Hp.

There was a post a couple of years ago regarding this, and I believe someone had also did some dyno runs with the different exhausts to see any variations in Hp vs torque.

If you want to get your car louder, then I would consider a sports cat (with less restriction than standard) but a complete Cat bypass and your G-pipe will probably be very loud. But we all have different opinions on what is loud and too loud don´t we. :-)

fstockcarrera

The cup setup is sport cat with primary and secondary by passes. Too loud for the street. The Euro premuffler and primary bypass is a good set up and gives up 6 rwhp to all bypasses.

Bob

etom

kusee pee: I tried the g-pipe with the primary and couldn't stand the loudness for more than 10 seconds. It really is a racket!

Does anyone run a primary bypass with cat bypass? I presently have the primary and am comtemplating adding the cat bypass as well. What is the effect, if any, sound-wise?

thanks in advance

964rh

Etom

Mine runs at present the cat and primary bypass with the original sec. silencer.
Imo, the sound is great, not too loud, plenty of popping when you lift off the gas, sounds almost smooth when your booting it. Sounds a lot more compressed than the g pipe did ie not ,much burbling(if that makes sense???)

Velomann

etom,
i have a cat bypass that i have not used or installed as of yet if you would like to try before you buy. i have only done the g pipe secondary silencer removal with an airbox and mine is plenty loud and throaty.....but it is also a 3.8 motor. i am in seattle, so if you would like to try, we can try to hook up and hand off the pipe for a trial.
don.

etom

Hello Don in Seattle,

Yes, I wouldn't mind having a go with your cat bypass? What brand? I am not sure how we might arrange a meeting--though, as the crow flies, we aren't that far away. If the Mariners were playing I could find an excuse.

kusee pee

Cheers for all the advice guys. Despite the warnings about being too loud I am mindful to go for the primary and secondary bypass. I want it loud as hell, the louder the better. With the g-pipe as is it is great noise with the windows down but pretty quiet otherwise. And I want noise!

964rh

Go the old school way and drill some holes in something

TR6

Let us know how it works out. And you may want to buy some earplugs to keep in the glove box.

For what its worth, with my secondary bypass, cat bypass, fabspeed open air intake, and still retaining the stock primary, I really like the sound and volume level of my car. Even on a weekend trip that featured a 5 hour drive each way, it didn't bother me. But my wife did comment at the end of the weekend that her ears were ringing a bit. She said that next time, she's bringing ear plugs for a long drive. Or I guess I could always put the OEM cat back on for road trips...

ronone10

Hello Don and Etom,

I too am interested in trying a cat bypass and was wondering if I could possibly try it after Etom. I live in Seattle. I get my work done at Chris's German Auto in Belluvue and that is who I would ask to install it for me.

Thanks...