ScottArizona

Ok, got everything buttoned up late last night, test fit the bumper, cut the holes for the license plate lights and the license plate mounting bracket, and took it for a quick 15 min test drive.

Verdict: Ecstatic! I expected to love the sound, and was excited to reduce some weight, but I was BLOWN AWAY by the improved responsiveness, throttle response, and power! I expected to maybe detect a little more umph, but the difference, at least when compared to my prior set up (fabspeed headers and unknown brand mufflers) was pretty dramatic. Car is noticeably quicker. Throttle response is WAAAAAYYYY better, and the sound is perfect! No CEL's, so no problem reversing the position of the post-cat o2 sensors side to side (just make sure you keep them in the post cat positions).

I'll post a new thread with some sound clips and a summary of the diy and my impressions, but wanted to update this thread as well. Other than the cost (and for some, the loss of purity), I think there is no reason not to do this! I'm stoked, and really, really endorse this conversion!

As for the questions above, here you go. I've attached a pic showing how I dealt with the bumper bar and heat shield. Nothing elaborate. I may try to source a 997 gt3 heat shield and cut it to more perfectly follow the outline of the cup bumper. I'm not going to use a tow hook as the oem cup hook requires that you loose the bumper bar, and I'm not willing to do that.

I am using the fabspeed "dual outlet" style side bypass pipes. When I ran a side bypass set up on my old 997.1 gt3, I was using the bbi single outlet/block off plate style. I can say without reservation that the fabspeed style on a 996 drones significantly less than the 997 with a single outlet style. Very, very little drone with this set up. The volume is also not at all insane. I don't know if he would pass sound at any of the popular west coast tracks, but I'd be surprised if it didn't as its really not that loud.

Sknandigam, I like your idea of modifying the c2 bumper. However, you can get the cup bumper to work just fine if you are ok with having a tow hook indentation in the bumper without a tow hook. I was a bit concerned that I wouldn't love the aesthetics of this bumper as its cut higher up on the bottom edge, thus exposing more of the muffler hardware, but I actually don't mind the look at all. Cant wait to get the bumper to paint and get everything buttoned back up.

If anyone is on the fence, I can't recommend this enough. Very happy!

knorrena

Scott,
Thanks very much for the thorough response. It was exactly what i wanted to learn and i am glad that you are pleased with the result.

Karl

PorscheG96

You will get catalyst not ready CEL in a couple hundred miles. I posted the fix here:

https://rennlist.com/forums/996-gt2-...ight=cat+ready

You'll need to extend the rear O2 sensors and cross them over. Also, there's a 996 cup heat shield available from Porsche pretty inexpensively.

ScottArizona

Holy crap. AMAZING post. So, I'm going to take a wait and see approach and see how long it takes for my cel to trigger. Since the condition you describe (and the resulting CEL) is really just a result of emissions diagnostic testing, and won't affect performance or reliability, I'll probably just clear any codes that appear. In AZ, not all readiness monitors have to be "ready" in order to pass emissions (I think you get two "not ready" indications). If it gets to a point where it won't pass emissions in two years, I'll extend the secondary sensors as you did.

For future reference, could you explain how you added the additional 30" of required wiring length for the post-cat sensors? Did you splice wiring, or were there bosch options that included the additional length? If the latter I'll just do that!

mmuller

Or just get a tune in the car that ignores the o2 sensors. The side benefit is an additional 12-15 rwhp you get from the tune.

Slippery slope!

AudiOn19s

I don't have a tune but my fab guy built o2 extenders for my secondary sensors and the only time I get a CEL is if I drive on the freeway for more than 20 min at < 3k rpm

...I don't have cats either.

993GT

get a couple universal o2 sensors and build your own harness after the factory connector, gives the length and correct sides

John@Fabspeed

Very unique setup! Glad our products could be of help in the build : )