whats all the numbers mean for some of the turbo specs, like a T04 turbo has a .68 compressor and a .84 A/R turbine. is this in millimeters? whats the stock dodge HX35W turbo #s?

 

A/R is the ratio of the area of the turbine scrolls (or the compressor scroll) to the radius (how far from the shaft they are at that point). The smaller the A/R of the turbine housing, the quicker the spool.

Holset uses an area of the turbine scrolls at some unknown point. The smaller the area the quicker the spool. That's why when HTT or II sells an S300, they say the housing is "equivalent to a 12cm", because Borg Warner uses A/R, and we're used to cm^2.

A stock HX35 should have a 56mm compressor inducer, 83 mm compressor exducer. The turbine wheel is somewhere around 65mm on the inducer and 57mm on the exducer. The turbine housing is 12cm^2; I'm not sure what A/R that would be.

 

reason I ask is I have this cummins reman turbo that is supposed to be similar to an HT3b but I can't find any info on it. heres what I got with my trusty tape measure:

compressor inducer- 74mm
compressor exducer- ?

turbine inducer- ?
turbine exducer- 91mm

5 inch exhaust flange
5 inch intake side

4.25x3 bolt pattern on exhaust inlet side

 

The compressor inducer sounds similar to an HT3B to me. IIRC when they're used in twins they have (generally) a 74mm inducer. Sounds like it might be a good bottom turbo.