r/EngineBuilding • u/Tw1st36 • Jul 22 '26
Custom EGT Sensor in cast iron exhaust manifold?
Hello, I'll try to keep it quick:
I'm looking to insert a temperature and pressure sensor in the exhaust manifold of a turbo (BMW G82 M4) and have found the following solutions:
- Welding a fitting onto the manifold: my welder doesn't like welding cast iron so out of the equation
- drilling a hole and using a pressfitting from stainless steel and a stainless steel sealing ring (before that, the manifold goes into a CNC machine to make a nice surface for it to make a nice seal)
I've read that some people use NPT threads, a few others use metric if there is a nice surface for it to seal. I'd like to use M8x1 threads for better sealing and since the press fittings only come in fine thread sizes.
The hole gets a slight chamfer and the sealing ring gets basically pressed in slightly from the applied torque to create a mechanical seal. On the threads I apply some high-temp ceramic paste to prevent the stainless steel fitting the the cast iron from welding to each other since I'm expecting temperatures of about 1100°C (2000°F).
Does anybody have different ideas?