Reducing exhaust fumes from cammed L77.

[RevNev]

some tuning that not many shops do or understand can help with the smell, but at the end of the day if the cats arnt burning the emission it will smell, but tune wise should be able to clean up alot of it

It's common to de-cat the F Series M3/M4 BMW's and the exhaust smell is minimal compared with de-catted or 100 cell Commodores. The BMW's run dual wideband lambda trim off each turbo and idle at 1.00 lambda and unless you rev them up a bit in an enclosed shed, you can't really smell the exhaust much to consider they're likely de-catted. They remain at 1.00 lambda pretty well until they come on boost and switch down to .89 through the rev range. Great mixture control for a stock ECU system!

 

[Jeda]

Fumes have always been an issue with mine.

Went from 100 cel to 200. Made zero difference

That's what I hear too, which is why if I'm going to redo the cats, may as well go for a 400 cell if I can fit it.

The headers I've got are meant to allow standard cat back fitment. I'm trying to find out if I can run an oem cat set up with modifications to suit an aftermarket catback exhaust.

I'm just gonna take it to an exhaust shop and ask what options I have.

 

[RevNev]

I'm trying to find out if I can run an oem cat set up

I don't think there's enough room for OEM size 400 cell cats with long tube headers.

 

[Jeda]

I don't think there's enough room for OEM size 400 cell cats with long tube headers.

Are my headers considered long tube though? They arent shorties, but boubt there's much I can do because the aftermarket ones are 5" round. I'll take it to an exhaust place and see what options are available. If there aren't any, I'll just get it retuned.

These are my headers;

 

[daves8]

You’ll find that the cats make a huge difference to sound and headers equally as much.

Of course if you fit a standard cat back you won’t notice much difference in sound at all.

Maybe I’m just more particular than others when it comes to the sound of a v8?

I have often thought Difillipo 1 7/8 headers would sound better (more beat / note separation) than my 1 3/4 Rex short 4-1s

What does the cat do to note in your mind?

 

[daves8]

Are my headers considered long tube though? They arent shorties, but boubt there's much I can do because the aftermarket ones are 5" round. I'll take it to an exhaust place and see what options are available. If there aren't any, I'll just get it retuned.

These are my headers;

View attachment 251934

Do you have any drone between 1000-1100 rpm with yours?

I have the same headers

 

[losh1971]

It's worth fixing the tune though. With a good proper tune it will be better all round.

 

[RevNev]

re my headers considered long tube though? They arent shorties, but boubt there's much I can do because the aftermarket ones are 5" round.

These are VF2 Euro 5 cats (pretty restrictive), but I think too big to fit behind your headers.

 

[Jeda]

Do you have any drone between 1000-1100 rpm with yours?

I have the same headers

I get a bit of drone at around 1600 to 1900 now. Before the cam upgrade I was getting drone everywhere under 2500rpm. I'd say it's more my catback being responsible for the drone. I have an xforce catback. I can't stand the sound anymore. The only time I don't mind the sound is when you floor it. Everywhere else it sounds like crap.

Have you got the Rex 1 3/4 headers or the triple stepped headers that have 3 pipe size differences. These go 1 3/4" to 1 7/8" to 2".

 

[Jeda]

These are VF2 Euro 5 cats (pretty restrictive), but I think too big to fit behind your headers.

View attachment 251948

There's no way they'll fit behind the headers. Even if you mod the pipe that bolts to the standard exhaust manifold, cutting it back almost to the cat body, it'll leave stuff all ground clearance. I might try picking a pair up if I can get them cheap enough and take them to an exhaust shop and see what they say.