993 exhaust layout needed for conversion

[Drdogface]

I'm trying to get an approved design for an exhaust layout for a conversion of a 993 3.6 into a '78 SC. I have been talking, twice, to a Ca. Smog Ref Supervisor for his advice. He asked me to find a more or less detailed layout of the stock 993 exhaust so he can advise me. I told him the basic layout as I know it but also that (I think this is true) the 993 cat is actually two cats contained in one housing. What I need, it seems, is a diagram of what's inside that housing and a diagram of the exhaust flow to show him. Then he can tell me how to lay out the new one with after market parts.

I dunno why these guys demand such detail as long as what comes out the pipe is clean, but that's just the way they are.

Now, it seems, I may need to find a new shop to do all this since I have not heard from my first choice in a month. Yeah, I was warned...oh well. Any advice on what shops in CA do good work on this will be appreciated.

[Brando]

Don't talk to a shop unless they are specific to Porsche. Most others will take your money and be happy to send you to the referee to get turned away as non-compliant.

The best thing to do in CA is have the stock setup (as restrictive as it is) with a CARB approved Catalytic Converter waiting for that bi-annual emissions test. Then when you pass with flying colors, swap it out for your 993 HEs and muffler.

[Drdogface]

I wouldn't THINK of taking it to just any old shop. It must be a highly recommended P car shop that does this all the time. I know of a CARB approved cat by Magnaflow. What I don't know is the layout/number of cats/exhaust flow pattern of the stock 993. Thanks Brando

[mnmasotto]

Forget the CA Smog Referee!!!! They are a big headache and way too much of a hassle. My Fabspeed Exhaust with cats passes the usual local smog shop visual inspection without any problems. The car definitely passes the sniffer test becaust the 3.6L motors tend to run a little cleaner than the older engines.

[ischmitz]

The general layout is that the outputs from both HE's go to the center mixing chamber with the oval cover (the single O2 sensor is located on the other side of that chamber). The mixing chamber has a cat element attached at either side (2 identical units) and from there it goes into the mufflers.



I am surprised that CARB is asking you about the 993 layout. I always assumed CARB would use the exhaust layout from the receiving car. Believe it or not but the exhaust is considered part of the chassis and not part of the engine for emissions purpose. So you should duplicate the 3.2 or 964 layout with crossover and single cat.

Ingo

[Bill Verburg]

Here's the patent diagram

[Drdogface]

Bill,
Thanks...that's perfect ? What is the source of that pic and do you have the key to all the numbers shown ?

I'll never understand CARB and their demands. The exhaust layout with regards to the cats is of concern to them but mufflers are not. I'll never understand their thought process and demand for duplicating the layout if the exhaust is clean at the tail pipe. Makes no sense but that's govt

[Bill Verburg]

Originally Posted by Drdogface

Bill,
Thanks...that's perfect ? What is the source of that pic and do you have the key to all the numbers shown ?

I'll never understand CARB and their demands. The exhaust layout with regards to the cats is of concern to them but mufflers are not. I'll never understand their thought process and demand for duplicating the layout if the exhaust is clean at the tail pipe. Makes no sense but that's govt

From the United States Patent Office, Patent Number: 5,325,666
send me a pm w/ your email, I can send you a pdf copy