Turbo size question

[dvieira]

Hello...



when it's mentioned that a turbo is a 12cm or 14 cm or 16 cm, exactly where is this measurement at, on the exhaust portion of the turbo or the fin size or exhaust inlet, i've been confused on his since day one...



thank you



dave

 

[Forrest Nearing]

it is a measurement of the inside dimensions of the turbine housing... the smaller the number, the smaller the "nozzle" that the exhaust gas has to pass through before it passes over the turbine wheel. smaller nozzle means earlier spool up, but more restriction and higher EGT's at higher RPM/power levels

 

[BPonci]

Area over radius.

 

[Forrest Nearing]

well, I was under the impression that the Holset measurement in mm was an actual area measurement... be it average or whatever



whereas the garrett A/R is a ratio number...

 

[dpuckett]

Forrest, you are right about the Holset number. It is, I believe, the area of the point where the scroll comes back into itself. You know, just past where you can get to with a die grinder to port some more :{



I'm still somewhat lost on the Area over Radius measurement.



Daniel