Turbo measurement questions

[AMink]

I see on different posts different sizes for turbos, ie- 14, 16 cm. What is this actually a measurement of? Is it the size of the pinwheel? And do the smaller sizes spool faster, but ultimately move less air? What is the stock size for a '97? Thanks

 

[SRadke]

A stock 97 truck will have a HX-35 turbo with a 12 sq. cm exhaust housing. The 12 is the square area of the housing that the exhaust must pass through before exiting out the exhaust pipe. The turbine will be spinning in that area and the exhaust spins it.



A smaller housing will leave less room around the turbine for the exhaust to pass htereby making it spool harder/faster. This will also create more backpressure (drive pressure) in the exhaust flow and have diminishing returns as the power is increased. with more power you open up the turbine size to allow more flow but give up some of the instant spool on the bottom end to gain the extra power at the top. Turbos are very much give and take.



On the other side is the compresser. It is measured usually in mm and you refer to the diameter of it. A stock turbo is around 56mm with a larger performance turbo being usually in the 60-66mm range. Large truck turbos like those used in twin applications will measure 3. 5-4. 25 inches generally.



Sombody correct me if my numbers are very far off



-Scott