1984 BMW 318i

Why you don't use header tubing for a turbo or wrap a turbo header.

These are a couple photos of the header I made for this turbo project.  I bought the header flange (part# 130022338) to bolt to the head and the mandrel bent 1.5" tubing (part# 175630305) from Stahl Headers. The T3 turbine inlet flange (part# 30263) was purchased through Turbonetics.  The header is wrapped with header insulation to reduce heat loss.  After several months of driving however, the header developed a leak.  I removed it and found that the metal under the heat wrap had overheated to the point where the pressure inside blew a hole in it.  The metal had begun to flake off under extreme heat.  The parts of the header that were not wrapped were OK.  After repairing the damage, I painted the header and reinstalled it.  I found out later that most header makers void all warranties if header wrap is used.  I can't feel any difference driving the car with or without the wrap.

Prior to paint and wrap.  The front 2 cylinders go into a single pipe.  #3 goes up, makes a 170 bend, then points directly into the turbo.  #4 is extremely short and makes a 90 degree bend.  The header flange is welded to the turbine flange.  The turbo sits at a 25 degree angle to the head.

Painted with 1500F paint and wrapped with special header wrap.  Don't ever use header wrap on a turbo header!!!
After driving it another 6 months since the last header repair, the tubes were completely shot.  They started cracking and bursting everywhere.  I finally broke down and removed the header to rebuild it.  This time I bought 1-1/2" schedule 40 weld pipe and elbows from McMaster Carr.  They have 2 different bend radiuses available, 1.5" (part# 43425K157) and 2.25" (part# 43425K151).  They also have the 45 degree bends and of course the straight pipe.  This tubing is 0.145" thick and is designed to be welded together.  The inner diameter is actually 1.61" so it is really bigger than 1.5".  This is the most common, and most commonly recommended, material for building turbo headers. I learned the hard way that regular header tubing will not work!

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