I have run every possible exhaust configuration on my car. I now run a pair of RandomTechnology catalytic converters.

Conclusions;

Before and after emissions show a staggering change in emissions.

Dyno shows no perceptible change in HP. Possible slight torque increase at lower RPM's with the cats.

Absolutely no increase in running temp with the cats.

your 3.6 is an entirely different animal though.

Truth, Amen brother!:cool: http://www.pelicanparts.com/support/...s/beerchug.gif

There's an interesting quote from the earliest Spanish explorers about the LA Basin's pollution phenom.

The EPA, founded by Richard Nixon, and the various federal and most state air quality laws today are all about power, controlling people, and stealing money from them.
:mad:

My 3.3 Turbo clearly ran 10-15 degrees cooler (oil temps about 175-180) without the CAT.

My turbo spooled faster too.

Please post photos of your installation.

Yes, good point. Mine was 130,000 miles and melted.

I still think it ran cooler sans CAT as the air (exhaust) wasn't restricted on the way out the back. It is pretty well known the turbo will spool faster without the CAT (dunno how much quicker though...).

Some data points to chew on:

3.5L Motronic twin-plug motor that runs PERFECT

with stock heat exchangers & catalytic convertor:

HC @ 15 mph (PPM) - 13
MAX allowed - 121

HC @ 25 mph (PPM) - 8
MAX allowed - 96

CO (%) @ 15 mph - .04
MAX allowed - .76

CO (%) @ 25 mph - .03
MAX allowed - .65

NO (PPM) @ 15 mph - 283
MAX allowed - 807

NO (PPM) @ 25 mph - 290
MAX allowed - 746


Now, with headers installed & no provison for catalyst:

HC @ 15 mph (PPM) - 95

HC @ 25 mph (PPM) - 90

CO (%) @ 15 mph - .44

CO (%) @ 25 mph - .44

NO (PPM) @ 15 mph - 769

NO (PPM) @ 25 mph - 743

Conclusions? The motor still passes, but just barely!

1. Motor is down on power with stock heat exchangers and catalyst installed due to exhaust restriction.

2. Motor runs much hotter (not good) with stock heat exchangers and catalyst installed. Approximate oil temp at 210-220 versus 195-200 with the headers.

3. Removing heat exchangers & catalyst and installing headers significantly sheds weight. Even removing just the catalyst in favor of a pre-muffler will shed some unwanted lbs. and the car will run slightly cooler. BTDT.

Do what you feel is right and best for you.

Ralph

Moses, do you have any photos of your latest configuration? All I found was the sharpie version:

http://forums.pelicanparts.com/showthread.php?s=&postid=593993&highlight=Random+T echnology#post593993

if you would rather not post them you could email me through the board.

Thanks,

I tried ('87) both the straight pipe cat elliminator from Bursch and the Dansk premuffler. The cheapo Bursch gave a noticable performance improvement, especially top end, while the Dansk actually seemed to do nothing at all for performance and it weighed more... My vote is for what works, the Bursh straight pipe, at half the cost. BTW, good idea to have it aluminized because the paint it comes with just burns off in a few days allowing it to rust.

Kevjandon,

I have an 82 911SC. When I got the car, it was fitted with an aftermarket converter and the stock muffler.

I have experimented with a Fab Speed pre muffler (flange welded @ incorrect angle - different story) as well as a Dansk single in dual out.

Summary:

1. Adding the premuff killed throttle perfomance. I now run the cat as top end is the same with increased throttle response and low end.
2. The pre muff was quieter. A little different sounding, but not loader.
3. I now run the cat with the Dansk for the best of both.

I have read that the Porsche version of the Euro Pre muff (Dansk same) performs better due to the volume of the enclosure. Fab Speed and straight pipe both have lower volumes. Might limit velocityandflow?

Additionally, keep in mind the O2 sensor needs heat to light off. Without converter, may cause issues.

Any newer style cat should flow well. Gains in removing the cat depend on how inefficient the unit is in the flow department as compared to the pipes, pre muffs, etc.

Marlin

Kev,
You musta been watchin the one on ebay that ended tonight...Were you the winner?

I considered it, but I elected to pass. Seems like money is better spent the muffler.

Re: Re: What does a cat bypass pipe get you?
 

___

Any problems with passing emmissions wht the metal core?

Re: Re: Re: What does a cat bypass pipe get you?
 

Not with mine. Great performance. Do a search for "Random Technology". I posted before and after #'s.