Custom exhausts / oval exhausts

[nik.]

Not sure if this belongs here or in fabrication but I'm more concerned about the technical side of this , so here we go

 

I run a 1j 180sx drift car with a borgwarner s360 with plenty of custom shit 

I'm trying to make a 4" dump that merges to a 6"x2.5" oval section just under the front of the car and when it crosses under the tunnel (as a jz exhaust crosses under the car on any nissan) at the rear of the gbox it merges to 3.5" tube and points straight to the rear of the car 

 

I'm just wondering if anyone has any feedback in terms of performance or flow or any characteristics worth noting/ any discussion by making an exhaust like this 

I'm struggling to beat the metal to make it perfectly smooth. There is clearly some edges around the added in piece to make them merge but again, I dont think I'll encounter any issues, I'm just looking for any feedback/ discussion/ personal experience with changing exhaust dimensions/ shapes

 

 

 

 

And 1 bay pic because nothing is anything without pics ?

 

 

Cheers!

[iruvyouskyrine]

It won't be an issue. Also poewredbymax sell oval exhaust off the shelf i believe, but it looks like you have most of it done already.

[nik.]

I actually wrapped it up today 

Was more interested in if it would disturb exhaust flow going flat or lose velocity, or if running a twin 2.5" would be beneficial because round etc

I always read about "properly designed exhausts" but my take on a turbo car was just let it flow as much as it can 

 

Anyway, I guess there is nothing to gain. I've made it now lol

 

[GTSBoy]

The very best shape is round, because this has the highest ratio of cross sectional area to wall area.  If you make it oval shaped, you get more wall for the same number of square units of flow area, so get more friction.  But provided you don't go too extreme (ie, keep the L/D ratio to about 2 or less, it shouldn't make a difference that anyone would notice.