What is difference/better bellmouth or divorced dp

[haruichi808]

Just curious there are so many types of dp and exhaust I just don't know which is better or what they do , I wanna go stage two headers up/dp n looking at q300 , but could someone inform me on bellmouth ?vs.divorced /catted n uncatted dp, and also thinking of tomei elh n up, if anyone has good reviews on that or something else

[scoobyscoodle]

Catted vs cattless is really a matter of what your emissions laws are, what you want to spend, and what you want to smell.

 

Divorced vs bellmouth has obvious differences in construction, as you can see by simply looking at them. There are arguments for either configuration from an engineering point of view. I personally went with a bellmouth style, but I have owned divorced DP's in the past, in real life I doubt you would be able to record any measurable difference in performance.

 

My personal argument against divorced designs, which are apparently supposed to increase laminar flow, is the gap between the actual turbine and wastegate flapper, and the DP flange. When the DP is mounted there's an empty air cavity between the turbo and DP, so it's not like the internal wastegate is sealed to the small pipe on a divorced DP. The argument here is that with high gas velocity the two exhaust streams stay separated, but I just don't see it making a large enough difference.

 

From a practical standpoint, there are definitely issues with some turbos and some divorced DP's in terms of iwg flapper clearance.

[Max Capacity]

Both my DP are Invidia, divorced, both had to be trimed to get them to clear the wastegate. The one I bought used, even had to be trimmed. I took off about 1/2" of the plate.

 

So just get a bellmouth.

 

IMO you don't need the header.