1985 400i 5 spd / Long overdue / 12k Service

Forgive the dumb question of the day, but what are the 2 curved pipes at the connection of the headers to the exhaust, outboard of the main pipes? They seem to be present in some pictures but not others.
My 412 has somewhat less of the exhaust than it used to have, and to great effect, too, but my headers don't seem to even have the connections for these smaller pipes.
It all adds to the mystery of what my car should actually have in the way of an exhaust. It passed CA smog recently with the small cats you see in the picture, but at some point another smog tester might fail me for not having whatever else is supposed to be there. I can't find a CARB sticker anywhere so I have no idea. Image Unavailable, Please Login

 

Follow-up question - what are the hexagonal pieces on each downpipe? Top right of my picture.

The headers on the cars are a work of art, aren't they?

If only they were equal length, the significance of such a configuration I have only recently heard, pun intended.

 

You mean the balance pipe? If so, these were previously discussed in this very same thread.

These were used to tune the k-jet.

 

Ah, I had thought the balance pipe was referring to the cross connection "balancing" between the two main pipes.

What does the actual balance pipe actually balance then? Mine runs like a dream without them.

 

Presumably balancing pressure inside the muffler so as to allow better flow in the slotted portion of the tube and reduce stress on the muffler (all this with question marks...) .

Some cars do not have them, in some other cars they are "tapped".

 

The SPCs show that they got rid of the "balance pipes" on the 412 (only present on 400).

Those are typically referred to as the "exhaust sampling ports". They give a place to measure the exhaust gas from each individual cylinder to investigate if there's a problem (they are very rarely used). The actual hex headed threaded plug is Ferrari PN 110860 -- used on many F models.

 

I see you have added universal cats on your 412. How is the sniff test, and what are your CO NO values?

I will be installing cats as well as the smell is very pungent, I use many underground parking garages and without a cat is unusable.

Sent from my MAR-LX1M using Tapatalk

 

See attached for the emissions.

The engine had to be leaned out a lot, which was a function of adding the cats and would have been done irrespective of the smog anyway. I previously put on 2 in/2 out cats and they were annihilated within 500 miles as the car was running rich.

Running rich, without cats, with only the small mufflers you see to the rear of the new cats and straight pipes aft of the rear wheels, manual transmission and the confidence to wring out a recently rebuilt engine, is a deeply stimulating experience and IMO the most fun you can have with your clothes on and/or without psychedelics.

There is a definite loss of power with the cats and leaning out, perhaps 5%, but to my relief the car still runs very smoothly.

Image Unavailable, Please Login

 

Did you use 2 or 4 2inch cats?



Sent from my MAR-LX1M using Tapatalk

 

4 inch.

 

2inch cats, and 2 on each side?

Did you get them installed and did you notice a difference in the exhaust smell?

Sent from my MAR-LX1M using Tapatalk

 

You and Britward may be talking about two different "sizes" -- the size of the pipe diameter (2") vs the OD size of the cat body (4").

 

1 x 4 inch Cat on each pipe, and yes, made a significant difference in the smell.

Apologies for taking this great thread in a different direction.

 

Great, I will be getting mine installed next week. Will make a separate thread.

Sent from my MAR-LX1M using Tapatalk

 

How did you replace the boots and where did you source them?

Sent from my MAR-LX1M using Tapatalk