Well today I finished modifying the internal wastegate on my hx35 12cm housing. I used the info and pictures that were provided by got...DIESEL? except that I didnt go with as large of a hole and flapper. The stock wastegate hole is 3/4" or 19mm, which has a surface area of 283.5sq.mm. I opened the hole up to 1" or 25.4mm, which has a surface area of 506.7sq.mm. So basically I was able to enlarge the surface area of the wastegate opening by 44%, if my math is correct. The flapper that I made is 1 5/16" in diameter which is the largest that I could fit in the housing without machining it. It also required no modifying or removal of the stock flapper arm or linkage. I just had to grind off the stock flapper and weld the new one in place. Another thing that I did in order to allow the flapper to open farther is that I ground a notch into the backing plate of the turbo where the flap makes contact with it. I also removed the divider in the housing all the way down to the back of the wastegate hole and radiused the path to the wastegate hole in an effort to smooth out the flow. Let me know what you think.
Cory









Stock flapper over new one

 

78% increase in cross section.

Good job.

[edit]

BTW, top two frames are a touch dark. Easy matter to edit them.
Open pics up in a Windows photo editor. Click 'Picture' tab in the toolbar, choose 'Balance'. Move 'Gamma' slide to right one notch, and enjoy.

This way I can make even most underexposed pictures much better.

 

Great write up, thanks for sharing. Please tell us what you see for egt reduction and performance gains.

thanks

 

I will post results as soon as I get the head back on the motor and get the thing on the road again.

 

Very nice!