Scott-- I just saw the video of your autox. The car sounds great. Do you have any issues with the CEL coming on? Since there are post cat O2 sensors I am wondering if the car creates any fuel mixture issues as it sorts out the loss of the cats? I had 2001 ///M Roadster with the new M3 motor. I put Euro M headers on the car and it felt good but the dyno numbers went down. I even put on O2 sims but they could not get the car to ignore the loss of the cats. Your thoughts on how the Fab Speed pipes work on a 996?

 

I think he had the muffler bypass pipes.

 

My bad. I thought that it sounded louder than you would expect for simply removing the cats. But now that I am on the subject, has anyone used the FabSpeed cat bypass pipes?

 

I installed the muffler bypass pipes on my '02 996. I quickly removed them. My old car sounded like a UPS truck on steroids!!! You simply cannot put your foot on the gas w/o destroying your ears. Hmm, and I thought I was "hard core"!!! Cruising they're okay, but as soon as you give it gas - lookout!!!!

However, if you must have them, go to your local muffler shop and save a couple hundred dollars. While at the muffler shop, pick-out a pair of tips and have them fabricate your pipes. Seriously, this is exactly how Fabspeed fabricates his.

 

I know about 3 people with the setup, two on Carreras and 1 on GT3 and they are LOUD, the GT3 is mostly a track car, one Carrera is only a track car and the other is a daily.

 

i think i described the sound on my gt3 as a POwer wagon stuck in the mud.... loud, unpleasant and removed

 

I use Fabspeed bypass pipes, but I also have race headers, cat bypass pipes, and race cats. I also have very aggressive camshafts and rev. the car over 8K RPM, which gives my car a pretty distinctive pitch. I use different combinations depending on the sound limit of the tracks:
- Bypass pipes + bypass cats = 110+dB, very light, very loud, but max power. My all time favorite for the track… but I don’t recommend driving like this on the street!
- Bypass pipes + race cats = 107dB, still light, and great power. This is how I drive the car on the street…
- Race mufflers + race cats = 98dB, real heavy, less power… but still a nice sound if you want to keep your car more conservative on the street.

I personally don’t like running mufflers without cats because it’s still loud, but without loosing the weight, and I noticed less power than the bypass pipes + race cats combination. If you are using the bypass pipes with street/stock headers and cats, you get up to 103dB. By the way, if you use cat bypass pipes, you’ll need to turn off the secondary O2 sensors (ECU), so that the CEL doesn’t come on.

I really get a blast every time I drive my car, at the track and on the street, but I also admit that this is not for everyone. I guess it all depends what you are looking for…

 

GT-Racer--- You said that the CEL will come on with cat bypass pipes. I have no problem with the light as long as there is no loss of power. Is this a case where the CEL comes on to let you know that there is a problem with the cat but the motor still runs at 100% power or does the loss of the cat cause an air fuel issue as the motor attempts to correct for the loss?

 

Hi Salazar - My cat bypass pipes have only one provision for the primary O2 sensors, which leave me no choice but to turn off the secondary O2 sensors, otherwise they would read that there’s too much air and the MAF would try to compensate the ratio without success. It would also end up in a loss of power and some black smoke. The MAF may die, and the engine may also idle inconsistently.

 

My next obvious question is, how do you turn off the secondary O2 sensors? Also did you buy the cat bypass pipes from FabSpeed or did you have them fabricated at a muffler shop? Thanks.

 

To turn the sec. O2 sensors off, you’ll have to remap the ECU. At the same time it is worth adjusting the ECU for additional power if you add cat bypass pipes, racing headers, modify air intake or throttle body. Even though the computer will adjust and learn from some of the modifications, tweaking the ECU will result in substantial improvements (make sure you mention all your mods to the person that will remap your ECU). My cat bypass pipes were built by Gemballa, they are very light, have an optimal length and provision for primary O2 sensors. It takes me about 30 minutes to swap cats with the bypass pipes.

 

I forgot to mention the option to change the RPM limiter when remapping the ECU. It’s a personal choice because of warranty issues, but it makes such a difference to have a larger range on the track.