Here is a turbo elbow and downpipe I made for a friends evo 9.

I have noticed that most elbow-downpipe combos do not have a flex or a slip joint where the stock O2 has. In my opinion this is a problem because you have a long piece of exhaust between the turbo and flex joint (which is then in the back) that applies large moment onto the turbine housing. Possibly inducing cracks in the manifold and/or making turbo bolts loose..

I have made this 76 mm elbow with Vband + short flex joint + a large flex joint in the back, under the crossmember. It is 76mm trought... The lambda boss is moved to a new position right after the sump. I have never understood why it should be right behind the turbo.. (if you do not have a precat..)

 

Nice fabrication work. The reason the o2 sensor is on the turbo elbow, is because the further the exhaust gasses go from the turbine wheel the more their density, pulses, temp, etc change, thus giving a less accurate reading.



You are right about the cracking on the manifold, the flexing and weight of the elbow and downpipe can impose, I've seen it happen so many times, especially on tubular ss manifolds, not so much on properly built manifolds, but way too many times on cheaper ebay ones. I have eliminated completely the flexing of the downpipe by welding a bracket on the dp and bolding it on to the car.




Marios

 

looks nice is it 3inch all the way through?

 

it is 76mm OD all the way... 2.5mm wall, so 72 mm ID

 

I know, although it is mostly because of emissions regs.. I have to say the car works the same with the o2 in both locations... and works better (smoother idle) when I turn it off..

Have to switch that car to SD because the combo of gsc s2 and hks turbo and MAF makes idle a bit messy..