![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
#26 | |
Comes with a free Frogurt
Join Date: Dec 2009
Location: Torrance, CA
|
![]() That is a nice solution, especially for packaging an external gate with a stock style manifold.
Quote:
I don't have any personal experience with that exact housing but I can ask them for the scoop if anyone's seriously interested... |
|
![]() |
![]() |
![]() |
#27 |
Ronald Culberbone III
Join Date: Feb 2010
Location: Portland, OR
|
![]() To me it seems like the oversized throat width would cause the 28 series turbo to be a bit slower to get moving, but have higher overall flow capacity.
Is that a correct assumption?
__________________
Cult Person. Pissing in your Kool-Aid. |
![]() |
![]() |
![]() |
#28 | |
Comes with a free Frogurt
Join Date: Dec 2009
Location: Torrance, CA
|
![]() Quote:
The nozzle is the thin little ring between the volute (scroll) and the wheel inducer (major diameter). Throat width is the axial width of the nozzle, along the direction of the shaft. The nozzle area would be pi*(inducer diameter^2)/4 x (throat width), approximately. I think what happens with response is that the housing will act like a bigger A/R than it physically is, because the flow is not being accelerated as much in the nozzle. Un-shrouding the wheel a bit means more of the wheel is acting as inducer; it extends past the corner of the blade to include some of the contour area. The wheel wasn't designed to work that way so it will likely reduce turbine efficiency. Velocity vectors at the inducer will be "sub optimal." Flow velocity at the turbine inlet would be reduced, and the amount of power you can make from a turbine is directly proportional to inlet velocity...so you'd now need a higher turbine pressure ratio to make the power your compressor needs. The measurable effect would be higher exhaust manifold backpressure vs. what you'd get with the same A/R but smaller throat width that matched the wheel inducer width. Overall flow capacity most likely won't be affected. Usually the turbine stage chokes in the volute - i.e. the only thing that will increase flow is a larger A/R, up to some really large maximum A/R where it will start to choke in the wheel. |
|
![]() |
![]() |
![]() |
#29 |
Comes with a free Frogurt
Join Date: Dec 2009
Location: Torrance, CA
|
![]() Throat width is represented by the little yellow line I drew in the turbine here...it's a twin-scroll but same idea, just ignore the divider wall.
![]() And then a nice simple diagram I found on a University of Cambridge site to illustrate what I'm jabbering about. This is a cross section through the turbine centerline. Flow is coming "out of the page" in the volute but spiraling in towards the turbine inducer. The volute itself is off-screen up at the top. Throat width is the left-to-right width of the inducer (section I) plus the clearance, and the shroud is the little bit of housing that follows the wheel contour as you move downwards and rightwards, along "meridional length S." Increasing throat width basically just removes the inlet part of that little shrouded area. ![]() |
![]() |
![]() |
![]() |
Thread Tools | |
Display Modes | |
|
|