herman maire

I dont think you should be smelling like fuel on a modern EFI car just because you deleted the cat.... they burn pretty clean AS LONG as there running right . If your smelling exhaust or fuel in the cockpit you have other problems. You should not be smelling like exhaust unless you hang out around the tail pipes, but like I mentioned I gutted my cat and the only time I smell the exhaust is when I am reversing with the windows down. When on the road I smell 0 fumes/ fuel smells.

I have a question for the pros here.... when looking at the cat bypass pipes offered what bothered me was that the O sensor was on only 1 pipe for the 95 year cars, that would mean its only taken the reading from 3 cylinders. Thats why I decided to gut my cat.... I ended up loosing 14lbs just from the guts of the stock cat and the O sensor is still right in the middle of the 6 cylinders. I think the sound changed also because I have a more metallic sound/ older 911 sound.

what do you guys think?

TroyN

I was sure mine was also running very rich after my Fabspeeds. But, I took it to a dyno and the operator said, nope, smells like it's running perfectly, and that was borne out by the a/f graph on the dyno runs. I was considering going with 200 cell cats because the smell was getting to me... after 2 years. I drove with the recirculate button switched on, which helped.

Stealth 993

I say something is wrong. You should be running the same fuel amount either way. Of course with the increased airflow, it will use a little more fuel. Maybe the MAF doesn't like the new airflow & is dumping fuel to match the higher flow, or maybe the O2 is reading leaner, & thus dumping more fuel.

Can't you track the MAF & O2's threw the ODBII port?

Also, most new exhaust pieces have a coating on them that burns off in time, so they stink pretty bad for a while.

fast_freddy

I have the same setup as the OP and it runs a little rich but nothing objectionable. With full on non-ethanol gas I get 27-28 mpg at 65-70mph on the highway and perhaps 16-17mpg city. Both those numbers are at most 1-2mpg less than when I had a cat. Me-thinks that his poor mpg are unrelated to the lack of cats and related to something else perhaps a heavy right foot as it sounds so terrific when you're on it without a cat.

ferdie993

yup, i agree with all the guys said. am using fabspeed myself in my C2, when it was newly installed the odor may smells differ from the previous original pipe without the catalytic converter. good luck!

daltvater

Thanks that is a really nice offer give me a few days and I may take you up on it. I'm going to have my mechanic (John Walker) take a look at it in a few weeks. I'll wait to see what he says. I wouldn't want you to go through the hassle yet. Thanks though.

Amazing. No resonating and it's only loud under full throttle.

daltvater, also in regards to the "backfires", do you mean more bite and burble perhaps? It's normal for cat bypasses to burble and pop on decel.[/QUOTE]

Twice I've got it to sound like a gun shot. (Loud enough for people on the sidewalk to duck) Other than that it's just the normal popping. Can't wait to see what John Walker says. I'm assuming he's going to say I'm an idiot and to put the cat back on.

NP993

I highly doubt it. John's a smart guy and will get to the bottom of things. Put it this way: if every time someone put cat bypasses on his 993 the result was gunfire-sounding backfires, half the posts on this forum would be about cat bypasses. But they're not. Something's obviously wrong.

daltvater

Good to know I guess. Looking forward to finding out what's up.

In the short term is it ok to drive? There are vintage Porsche races up here this weekend and I really wanted to take the 993 over the Rabbit!

Wilder

+1 on Noah's post. You should only be hearing the sweet sounds of burble and pop...no true backfire. I had DACH-X and RSRs which should sound similar to your setup. Here's a couple of clips:

Juha's DACH-X/RSR:
http://youtube.com/watch?v=GAxG_UnSE...eature=related

Matt's DACH-X/RSR:
http://youtube.com/watch?v=tjgps6LST...eature=related
http://youtube.com/watch?v=VDzXoHYtO...eature=related

daltvater

I just checked out those sounds clips the RSR's sound better than the fabspeed mufflers, no question. Yet another part to put on my list.

mbb993

+1
Know the smell and it's not right. As Bill et. al said. Drove cars before cats, some with 200K miles, but experienced nothing like this.

I had the same problem when I first put on the cat bypass. But, I was getting an intermittant o2 sensor CEL. (don't recall the code# offhand). After replacing the sensor it took quite a bit of drive time for the DME to readjust before the problem subsided but it did finally resolve.