Question On M3 & Cats (Also A Q On Akrapovic)

[hl0m4n]

the oem m3 cats are 400 cpsi correct? will a high flow 200 cpsi still give a code even when driving hard?

also is akrapovic planning on making a a catted version of their exhaust?

thanks guys.

[Lemans_Blue_M]

Originally Posted by hl0m4n

the oem m3 cats are 400 cpsi correct? will a high flow 200 cpsi still give a code even when driving hard?

also is akrapovic planning on making a a catted version of their exhaust?

thanks guys.

Yes it will still code.

The Akrapovic evolution system already has cats...

[hl0m4n]

Originally Posted by Lemans_Blue_M

Yes it will still code.

The Akrapovic evolution system already has cats...

thanks, the akra has cats? i thought they were resonators...why place the cats back there and not before and after the 02 sensors at the front?

is the "collector" in the diagram the cats or are they both resonators?

[Lemans_Blue_M]

Originally Posted by hl0m4n

thanks, the akra has cats? i thought they were resonators...why place the cats back there and not before and after the 02 sensors at the front?

The Akra exhaust has a set of cats before the X-pipe crossover transition, and a set of resonators after the transition.

Why did they place the cats so far downstream?

Two reasons...

1) By placing the 100 cpi metal matrix cats further back, it has a far less restrictive effect on the exhaust gas flow as it exits the headers. This also improves the scavenging effects of the exhaust system, which will yield higher hp/trq gains.

2) To reduce the smell of unburned fuel as it exits the tailpipe.

[Lemans_Blue_M]

Originally Posted by hl0m4n

thanks, the akra has cats? i thought they were resonators...why place the cats back there and not before and after the 02 sensors at the front?

is the "collector" in the diagram the cats or are they both resonators?

Read my previous post...

[hl0m4n]

thanks for the help man, so the placement is like like the csl exhaust. to be more specific if you look at the ss ones: http://www.supersprintna.com/product...earch_model/86 (enlarge pic)

there 02 sensors are before and after the cat. with this placement, will it pass and not give code?

[Lemans_Blue_M]

Originally Posted by hl0m4n

thanks for the help man, so the placement is like like the csl exhaust. to be more specific if you look at the ss ones: http://www.supersprintna.com/product...earch_model/86 (enlarge pic)

there 02 sensors are before and after the cat. with this placement, will it pass and not give code?

That's an interesting design, but I think the car will still code.

The length of pipe between the pre-cat 02 sensors, and the post-cat 02 sensors seem to be way too far apart.

I think the car will still throw a CEL for poor catalyst efficiency regardless.

You could be the giuinea pig though...and let us know if it actually works.

[rzm3]

Correct me if I am wrong...

The cats are downstream of the O2 sensors, so regardless of what kind of cats there are, the car will still throw a code because it cannot "see" the cats...

Still better for the enviornment though

[Lemans_Blue_M]

Originally Posted by rldzhao

Correct me if I am wrong...

The cats are downstream of the O2 sensors, so regardless of what kind of cats there are, the car will still throw a code because it cannot "see" the cats...

Still better for the enviornment though

Correct.

The high-flow cats on the Akra are downstream of both sets of 02 sensors, so the car will throw a code shortly after it's installed.

[mixja]

Originally Posted by hl0m4n

thanks for the help man, so the placement is like like the csl exhaust. to be more specific if you look at the ss ones: http://www.supersprintna.com/product...earch_model/86 (enlarge pic)

there 02 sensors are before and after the cat. with this placement, will it pass and not give code?

The rear O2 sensors are there to monitor emissions so if you have no cats in front you will get emissions CELS.

I'd say the rear O2 sensors can't be too far away from the exhaust manifold as they probably are designed to operate at a certain exhaust gas temperature and the exhaust gas temperatures further back will be much lower...

[Eugene-TAIWAN]

Originally Posted by mixja

The rear O2 sensors are there to monitor emissions so if you have no cats in front you will get emissions CELS.

I'd say the rear O2 sensors can't be too far away from the exhaust manifold as they probably are designed to operate at a certain exhaust gas temperature and the exhaust gas temperatures further back will be much lower...

ya, the second O2 is very close up front.

[hl0m4n]

the fabspeed one gives no CEL but the rear 02 sensors are located a bit differently compared to supersprint. they both use 200 cell cat though so the supersprint should pass right?

http://www.m3post.com/forums/showthread.php?t=314064

also based on this poll: http://www.m3post.com/forums/showthread.php?t=317820

and pictures of the encore, the encore xpipe has the same concept idea as supersprint in terms of 02 placement http://www.m3post.com/forums/showthread.php?t=236693