it is the other way around CAT serves a filter for emissions.....that is the reason you always check the mix before cat...and you go for test it is clean after the CAT;-)
Ivan

I mean that the CO mixture should be checked before the catalyst before removing it...of course - after removing the catalyst you can check it at the exhaust exit...
If he's unsure which mixture is adjusted it's alwas a good idea to check it before making any changes. So you can conclude if the engine is in right condition.

Thomas

I loved my Fabspeed bypass, but the fumes were not worth it.

On my 3.2 with the CAT delete the throttle response was amazing and the sound... perfect with the stock muffler... but the fumes at stop lights in LA were not worth it for me and the wife or any other co-pilot...

Now I run the stock Cat and a Fabspeed Supercup and couldn't be happier... still a little less responsive from a stop, but checks all the boxes and I can idle easy without the smell of fumes.

Be safe, Have Fun

you should not have any whatsoever fumes to smell ..really what gasoline are you using and what is the c/o set up?Also what is your cam timing set up ,if you do not have kick from 1000 rpm??

911 3,2 burns very clean....i even passed the smog once with the strait pipe in LA, but back in 2008...

Ivan

Using the sweet 91 octane w 15% ethanol that we get as CA citizens.

All I can say is my 3.2 has a smell that I don't like... so having a Cat is worth the benefit of an absolutely smell free cruise.

My car's fully in tune now, but I'll be running the Cat life personally.

-Ian

try to get toluene at the paint shop that will give the octanes you need.1/2 a gallon per half a tank..that is a sweet sauce..i used it all the time in CA

Ivan

Yup, fabspeed bypass was too smelly for me too. I opted for an active sport-cat and like it a lot. I've a 3.2 with CIS.

I find the comments about smell interesting and certainly contrary to my experience. But then, in my area 93 octane is readily available and gasoline is a maximum of 10% ethanol, unlike the above-referenced 15%.

In my '87 3.2 I am also not running a Fabspeed bypass pipe but am instead running a Fabspeed euro premuffler. Unfortunately, people are not always careful to distinguish these when referencing cat substitutes.

I've run this with the stock-style muffler and with a Dansk 1-in-2-out (84mm). The Dansk 2-out is a bit loud for highway driving so I switch mufflers depending on how I am using the car.

The Fabspeed euro-type premuffler has the bung for the OEM sensor and no re-tuning was needed, but I do have an SW chip (93 octane low-restriction exhaust version) in the ECU.

And because the premuffler gets hot and removal of the cat also meant removal of the heat shields, I wrapped the Fabspeed unit, like I used to do to muscle car headers back in the day.

http://forums.pelicanparts.com/uploa...1699060226.JPG

Smelly exhaust after swapping out a cat for a bypass pipe is often due to the engine being in a less than optimal state of tune. The cat will cover up a rich condition that would normally be looked after if no cat were present.

Replaced my cat with M&K pre muffler and muffler. Great quality and sound. Very pleased.
This on the '88 3.2.