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Thanks for the offers but I ended up just ordering the parts. Went with el' cheapo bellowed up-pipes and a 1.0ar housing for the gtp38. I will likely end up making a custom flange that bolts to the housing for the mid-pipe.
Got the 1.0ar housing in the mail today. Stock wastegate is a bit smaller than 3/4" (19mm) and only gates the passenger side of the motor.
First I drilled out to 3/4" and proceeded to cross drill into the driver's side bank of the housing. Next I removed the stock WG flapper. Then used a carbide cutter the open the main WG orfice to 1" (25.4mm)
Figure if im going to do this the biggest hang up will be the high pressure wastegate. 1" is a start but may do my best to make it larger.
I was just about to ask if you had made any progress and then you posted.
So you're going to bypass some of the exhaust gases to go straight to the low pressure turbine? Is that because the high pressure turbine is choked or because you want the low pressure turbo to light faster?
Mainly to keep exhaust back pressure in check. Not enough wastegate or too tight of housing can cause boost/ebp ratio that is far from 1:1 when the atmospheric starts making boost.
Brokestroke, if you find yourself in need of another OEM wastegate, I have one in my garage you can have for free.
Have you done any more planning for the tube routing under the hood in order to maintain "stockish fitment" as much as possible or just taking it one step at a time for now?
Brokestroke, if you find yourself in need of another OEM wastegate, I have one in my garage you can have for free.
Have you done any more planning for the tube routing under the hood in order to maintain "stockish fitment" as much as possible or just taking it one step at a time for now?
Thanks but I just got a new oem wastegate with the 1.0 housing. Will finish the housing and plate that bolts to it and then go from there.
What signal will you be using to control the bypass?
Boost pressure hooked to the wastegate actuator. Right now I have a 22psi oem actuator.
The 35mm wastegate is a little tricky. Had to completely remove the raise surface in the casting that was milled flat for the wastegate flap to seat. Then make the casting and new wastegate flap flat enough that it will hold back exhaust pressure. Colored the surface with a Sharpie and worked the WG flap back and forth on it. The high spots showed up in the Sharpie. Work them down gently with a stone wheel until flat. Works good if you hold the flap over the port and shine a flashlight into the housing, any gaps will shine light through. The wastegate arm with also need clearancing as well as a bit more of the casting.
Boost pressure hooked to the wastegate actuator. Right now I have a 22psi oem actuator.
The 35mm wastegate is a little tricky. Had to completely remove the raise surface in the casting that was milled flat for the wastegate flap to seat. Then make the casting and new wastegate flap flat enough that it will hold back exhaust pressure. Colored the surface with a Sharpie and worked the WG flap back and forth on it. The high spots showed up in the Sharpie. Work them down gently with a stone wheel until flat. Works good if you hold the flap over the port and shine a flashlight into the housing, any gaps will shine light through. The wastegate arm with also need clearancing as well as a bit more of the casting.
Throwing a wild idea out there. What if you modify a wastegate actuator to operate on differential pressure? That way the bypass control is a function of drive:boost pressure ratio rather than just boost pressure. You will probably have to run a lighter spring.
Still figuring everything out but basically just reading what typically works on a Cummins. One thing I can see happening is hot exhaust gasses messing up the diaphram in the WH actuator.
Thinking somewhere along these lines for parameters.
Hig pressure:
GTP38/1.0/35mm WG
Atmospheric:
S372 (or S475/T4)/1.0ar WG
44psi boost/50psi EBP
