Decided to remove the HF Cat and go with the test pipe

I'm super interested in how this turns out. I intended to replace my cat, then decided why mess with it since it was all working great. I'm not sure.....I have the materials to make up my own test pipe, but just haven't done it yet.

The gas smell isn't going to work out too well with my wife so I can't afford for that to happen.

 

I have pretty much a straight flow system with a euro car, no cats and a tubi. by "gas" smell, do you mean it smells literally like gasoline, or smelling "rich". Mine doesn't smell like gasoline, but smelling rich maybe on startup.

Ace

 

Mike or anyone..

I'm curious, assume your car is 328. Do you have 1 or 2 cats.. and are they the same as a 308?

I would love to get my hands on a 308 cat or test pipe to copy the flange etc.. to fab-up a test pipe.

Anybody have one they don't need or are willing to loan?

Thx

 

Interesting experience.

Mike996, did you perceive a difference between OEM cat and HF cat?

I read that HF cat supposedly flow as much as test pipe minus 3 to 5%. I what they claim is true you should not feel a big difference between your HF cat and Testpipe.

It might not be your goal to have a significantly better flow but to run it cooler, in this sense it will certainly make a good difference.

Looking forward the results of this experience.

 

328's that are Cat. equipped have only one. Don't know if they're the same as a 308's but I would guess they are not.

 

I'm not trying to answer for Mike but I did not notice any difference going from OEM cat. to test pipe so I would be surprised if anyone could notice a difference between different cats.

 

More cheap insurance and peace of mind. Also, I would assume, having it off the car prolongs its life. Then if you need to put it on later for a smog test it may very well still be fine and have plenty of "life" left in it.

 

I took my cats (1982 US) to a performance shop. They gutted them and added straight stainless tubes, proper diameter, through them. This was easier for them than simply welding the flanges onto the pipes, because of fitting without the car present. That is, I had the car in the body shop all Winter, removed the exhaust and cats, took them to the perf. shop and he did the work there, including new stainless tips, slightly larger and longer than stock. What I now have is a deeper rumble at low rpm, still no V8, I mean American muscle car V8, sound, but I love it. I THINK it runs a bit cooler at least the luggage doesn't melt! I had Dynamat installed under new trunk carpet as well.

 

Perhaps some people who make changes to their exhaust system end up with a rich smelling exhaust because they end up not re-fitting the 02 sensor back when done. I've seen a couple such muck ups....the 02 sensor just lying there tie wrapped to a convenient bracket. Of course, the mixture is going to be off if the 02 sensor isn't plumbed back into the new "custom" exhaust system.....duh....

 

If the smell of exhaust bothers you, I'll bet:


You are probably an anti-smoking zealot ...

and,


You probably should buy a Volt instead of a R E A L High Performace vehicle.


Just sayin'




I am running test-pipes. Cats were so clogged I honestly COULD NOT SEE THE SUN when pointed directly at it, thru them.

 

I've always been curious of this myself since the euro system did not have an O2 system feedback. Mine did with a hokey box with a "lamdba control" labeled on the front of it. The system has since been removed. But how does the euro system work and can the us system be modified to work ala euro setup.

Ace

 

Euro 328's did not have Katastrophic Konverters except for the Swiss market version. Is that the version you are talking about? I have always wondered about that. It had the Cat. but no O2 sensor, no frequency valve etc. It has been my understanding that a cat. needs a somewhat accurate "input" to operate properly and also so it lasts a long time. With no feedback (adjustment to the Air/Fuel ratio) I'm not sure how that happens.

 

Not a 328 but on my 84 QV (one cat) I installed a test pipe along with the Larini and I must say it sound so good and as far as smells goes sometimes I can smell a little fumes and sometimes not, I guess it depend on on the wind direction.

 

The smell of automotive napalm, "... smells like victory." Don't it tho?

 

While my '85 was having an engine-out major last winter had the cat cut out and replaced with a stright pipe (re-using the OEM flanges, which were pretty crusty looking but are working fine), with a bung for the O2 sensor.
The cat had puked over half of it's internals into the muffler; had to spend about 5 minutes twisting and turning the muffler around to shake out all the little chunks.

There's definitely a different tone to the exhaust, hard to say if it's 'deeper' or something else, I'd say it's a bit louder and more 'raw'. Anyway, I like it

 

Hi Ace,

I don't know about the euro setup. Most systems have static maps in the ecu which provide the basic roadmap of AFR under the various conditions, and this generally works pretty well as-is, however, the 02 feedback loop is a refinement that allows for better tuning on the fly in my experience. I know the CIS on porsche and mercedes with 02 loop depends quite heavily on the 02 feedback, and I would imagine the gtsi CIS is the same (it's the same basic system).

A failed 02 sensor can certainly mess the car up as far as emissions go - ask me how I know!

 

I had the cat removed and a test pipe fitted to my 84 308 last yr. Did it mainly to avoid the risk of fire from fuel leakage into the cat. I definitely notice it runs cooler than before, given the heatwave in the Northeast this summer. I don't notice a difference in smell, but then again, I love the smell old sports cars give off (gas, oil, leather)...smells like at the track and gets the adrenalin going.

The sound is a bit louder, the description of raw, is on point. When I am on the throttle in 4th it can get a little loud for conversation but then again, it is a good way to get your passengers to shut up and enjoy the music of the engine!

 

I would like to know, is US and Swiss cat identicals?

IOW if I would like to put a test pipe too on my Swiss Mondial is it the same part as the one Mike996 will put on his car?


Mike, you gave me an idea to try it also!!!


Cheers!