Modifications to Cast Iron Turbo Exhaust Manifold

I have an old exhaust manifold for turbocharging a vintage BMW and I'm
running into a trivial difficulty with the wastegate flange. It's a
two bolt flange with a 22mm hole in the middle for the wastegate valve
to seat against. It's a leeetle small and I'm worried about boost
creep (engine getting higher psi than intended due to bad flow out the
wastegate). So I need to modify the circular hole to be around 32-38mm
in diamter instead of 22. Options obviously are use a flycutter to
machine it out or simply use an air powered die grinder (low tq, less
chance of mangling it) to grind it out after stenciling a template over
the existing hole.
Thanks for your time,
Jason
Reply to
GriffithBuilt
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Die grinder will make short work of it with minimal chance of digging, gouging, slipping, etc. Not too mention skipping all the setup and clamping.
GriffithBuilt wrote:
Reply to
RoyJ
I had a similar situation with internal wastegate hole it TD05 Cast iron turbo housing. I took it to a machine shop and they tried to drill out. It did not work. The drill just spun there barely making a scratch. It appears that part of the housing got altered over the years by constituents of gasses passing through it. I ported other parts of this turbo housing using a die grinder and had no problem. Finally I put a ball shaped grinding stone in my drill press and loaded the feed handle with an elastic band. It took some time but three stones later I had a 1" hole. I would appreciate if someone could explain the process that hardened the wastegate passage.
Regards,
Boris Mohar
Got Knock? - see: Viatrack Printed Circuit Designs
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Reply to
Boris Mohar
I don't know what a "TD05 Cast iron turbo housing" is, but if it got hard then it was exposed to carbon and heat, and carbon dissolved into the metal.
GWE
Reply to
Grant Erwin
I wouldn't change it at all, unless you have to. I would install a boost pressure gauge and maybe an EGT gauge as well. They are inexpensive and chances of the stock turbo overpumping is slim to none, considering how conservative the factories are. Steve
Reply to
Steve Lusardi
|||| ||>I have an old exhaust manifold for turbocharging a vintage BMW and I'm ||>running into a trivial difficulty with the wastegate flange. It's a ||>two bolt flange with a 22mm hole in the middle for the wastegate valve ||>to seat against. It's a leeetle small and I'm worried about boost ||>creep (engine getting higher psi than intended due to bad flow out the ||>wastegate). So I need to modify the circular hole to be around 32-38mm ||>in diamter instead of 22. Options obviously are use a flycutter to ||>machine it out or simply use an air powered die grinder (low tq, less ||>chance of mangling it) to grind it out after stenciling a template over ||>the existing hole. ||> ||>Thanks for your time, ||> ||>Jason || || I had a similar situation with internal wastegate hole it TD05 Cast iron ||turbo housing. I took it to a machine shop and they tried to drill out. It ||did not work. The drill just spun there barely making a scratch. It appears ||that part of the housing got altered over the years by constituents of ||gasses passing through it. I ported other parts of this turbo housing using ||a die grinder and had no problem. Finally I put a ball shaped grinding stone ||in my drill press and loaded the feed handle with an elastic band. It took ||some time but three stones later I had a 1" hole. I would appreciate if ||someone could explain the process that hardened the wastegate passage.
Turbo manifolds are often made of cast steel. They get a lot hotter and carry more weight out at the end than regular manifolds. Texas Parts Guy
Reply to
rex
I've done this a number of times on Buick GNs and a die grinder is the only way to go... but...be careful to first mark the WG pucks contact area before you begin to enlarge the hole. More often than not, the puck does not close exactly centered over the existing hole in the exh hsg. Usually you'll see a carbon track there on the exh hsg to indicate where the puck hits it so grind an equal amount concentric with that carbon track to be sure you don't get into an area that the puck can't close off. As for the carbon hardening the casting, though I'm a machinist and not a metallurgist, I douldn't think that could be possible but repeated heat cycles can work harden the casting which in this case is what I believe has happened. Thanks, Steve Monroe
Reply to
Steve Monroe

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