rough surface inside of ta49?

[turbo buicks]

when i looked inside the turbine inlet on my used ta49 i just got it had a rather rough terxture so i took sandpaper and smoothed it out. what was this roughness? is it just from the exhaust that went through it over the years? was i OK in smoothing it out?

 

[UNGN]

Smoother is better, but as long as there is no loose rust, a little roughness won't hurt much.

Where it should be smooth is the approach to the wastegate hole. If you are using a stock elbow with a TA49, the wastegate hole is going to need to be as efficient as posible to avoid boost creep.

Make sure there is a smooth, sweeping radius inside the turbine housing to the wastegate hole. If the hole is stock sized and is straight with square corners inside (the puck side SHOULD have square corners), the odds are pretty good you will get some boost creep.

 

[turbo buicks]

what are all the ways i can avoid boost creep using a ported stock DP elbow and stock WG hole? i saw you said something about making the corners of the WG hole curvy or something. anything else i can do to help control boost?

 

[UNGN]

You need to make the stock sized hole flow as much as possible. To do this, you need to "port" the inside of the housing.

A square sided hole only flows 62% of the air of a bellmouthed hole of the same throat diameter. The idea is to bellmouth the wastegate hole to get as much flow as possible for a given throat size (hole is determined by puck size).

 

[turbo buicks]

oh. do i want bellmouth both the inside and outside of the WG hole or just the inside?

 

[UNGN]

Just the inside. If you bellmouth the outside, the puck will not seal.

 

[turbo buicks]

ok thanks UNGN