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The critical area can be found with the raised cast numbers on the outside of the turbine housing near the inlet. In addition to the outside numbers, some turbine housings have larger indented cast numbers on the inside of the turbine inlet. Hopefully the turbine housing has not rusted to a point where it cannot be read. The critical area is based on the casting not the machining of the turbine housing. A turbine housing casting can be used to make several machined turbine housings to match the wide array of turbine wheels.

Most are marked...12, 14, 16, 18 etc…but this is a generic designation. In actuality, a 12 cm marked turbine housing might actually be 11.2 by design...while others will be 12.4 by design. Hope this helps.
 

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That's correct ... 16cm.

MY96Z, That's correct... the 1st & 2nd numbers under the casting part number is the cm2.
 

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Look inside one of the exhaust runners also, the number is an inverted casting in there.
 

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Not Usefull Information
 

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I'm sorry, but why don't you just measure the damn thing.

;)
Sure, Charles, good idea un-huh: now just tell us where to measure and how to measure? :rasta:
 

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That's an excellent question.. Where's Charles?

Much easier with a single volute vs a twin volute...that inboard volute could be a little more challenging to measure than than the outboard...and then you will still need to know the actual diameter of the restriction.
 

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That's an excellent question.. Where's Charles?

Much easier with a single volute vs a twin volute...that inboard volute could be a little more challenging to measure than than the outboard...and then you will still need to know the actual diameter of the restriction.
You need to measure the area of the volute where it starts the scroll (A) and from the centre of the wheel to the centre of that area (R).
Divide A by R to get A/R.
Measure in centimeteres and square cm and the numbers will take care of themselves.

Jamming some plasticine or clay down the neck will be the easiest way to get the shape, cut that and draw squares on it to get the area.
 

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You need to measure the area of the volute where it starts the scroll (A) and from the centre of the wheel to the centre of that area (R).
Divide A by R to get A/R.
Measure in centimeteres and square cm and the numbers will take care of themselves.

Jamming some plasticine or clay down the neck will be the easiest way to get the shape, cut that and draw squares on it to get the area.
True.... :beer: but you will need to jam the clay down the neck about 70mm...for an H1C.

I prefer to measure it like a VG axial nozzle and take gage pins to confirm the volute opening closest to the turbine wheel blades tips (which will be about 4-8 mm up inside the volute). Then measure the radius from that point to the center of the turbine housing. With those measurements... its Pi x 2 x Radius x width(gage pin diameter) and then x 2 for a twin volute...

But I still prefer to read the numbers on the outside/inside of the casting:)
 

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The only time I've had to do it was on a compressor housing. The hole was round so I just stuck bigger and bigger drills down it till I found one that hit at the right depth.:dustin:
 
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