A/R and cm2

[Leiffi]

Did some rubber molds of 2 Garrett housings GT47 A/T 1.27 and GT50 A/R 1.41 , and Holset 27cm2 for reference , and measured their area.

I got Holset at 26.8cm2 so accurate enough.

1.27 was 28.3cm2 so maybe 28 or 29 , calculated backwards R should be then ~87-90mm

1.41 was 30.6cm2 so 30 or 31cm2 , R ~84-87MM

Tried to measure Holset R , it is ~ 97 so that gives A/R about 1.1

Shows how stupid way to give housing flow capasity in A/R is , if you keep A same but make R bigger , it gives smaller A/R number even if it should flow more because better flow angle into turbine.

[Archnemesis]

Wow! How do you have so much free time?

[Leiffi]

Got advice from my friend who is PhD of mathematics how to find centroid of that area. It is actually quite simple. So now 27cm2 Holset housing is about A/R 1.12

[joefarmer]

I'd always wondered what weird math was behind the A/R and cm2. Thanks for hte lesson.

[Leiffi]

Originally Posted by joefarmer

I'd always wondered what weird math was behind the A/R and cm2. Thanks for hte lesson.

When you calculate A/R you must convert everything to inches and square inches.

[Leiffi]

GT47 A/R 1.13 = 24cm2

[MoparRiggan]

if my exhaust housing is 14cm does this convert to .80 a/r ? sorry i am not educated on this.

[Leiffi]

Originally Posted by MoparRiggan

if my exhaust housing is 14cm does this convert to .80 a/r ? sorry i am not educated on this.

Hard to say , must find centroid and measure R.

I dont understand why A/R is given for users , it is only needed for housing manufacturing to get right shape.