To help clear up some confusion over nomenclature for turbos available for the Evo, here's some background info.

Some of the turbos for the Evo are sold as a "GT37R". This is confusing since they are simply BB T4 turbos. This is not to say they are bad, they are fine turbos. They are just not true GT37Rs, as described below.

The only true GT37R turbos (that is, a Garrett GT turbo with true GT37 turbines and GT compressors) available today are found in Garrett's Duramax and Cummins upgrade kits. These come either as a GT3782R or a GT3788R. These are built on the same center housing and ball bearing assembly as the GT40R.

If you wanted to use a true GT37R from these kits you would have to deal with their non-standard compressor and exhaust housings.

However, it has been rumored that these true GT37R turbos will soon be available with housings that will make them directly swappable with the GT40R. Imagine the confusion when they debut as they will be totally different than the "GT37R" that has been available for the Evo for quite some time!

 

Most "37R" turbos are BB but have a T3, not T4 turbine housing.

 

You can stick many turbos in a variety of housings (T3, T4, divided, undivided, etc).

The turbine wheel itself in a "37R" is a T4 and the center housing design is BBT4.

 

The vast majority of the "37R" turbos as used in, for example, AMS 37R kits, Buschur 37R kits, Shearer 37R kits, etc etc etc are T3 flanged turbine housings. This is important for other readers to understand, because the flange on the exhaust manifolds for these kits is T3, not T4.

Turbine and compressor wheels are neither T3 or T4 -- those designations refer only to the turbine housing.

Sure, you can find T4 flanged kits (like ETS), but one needs to remember that the flange on their header or cast manifold is the factor that dictates which turbine housing they will be limited to using. That was the point of my prior post.

 

See what I mean about confusion? Naturally it is important to know what turbine housing footprints (T3, T4, etc) are being used.

However, turbos are named primarily by their wheels. T4 turbo has a T4 turbine wheel and T4 comp wheel. A T3 turbo has a T3 turbine wheel and T3 comp wheel. A T3/T4 has a T3 turbine and T4 comp wheel. This even extends to the GT series too: GT3582R has a GT35 turbine and 82mm comp wheel.

The housing footprint does not dictate what the turbo is called. Otherwise we'd be calling all GT30Rs "T3s" and all GT40/42/45Rs "T4s".

 

Honestly a 37R is just a T04Z with a 4 bolt style T3 exhaust housing like on a 35R...

 

^Yup. Though I believe the T3 housing used is the 4-bolt T31 rather than the 4-bolt GT housing on the 35R.

T04Z, "GT37R", PT67R... all different names for a BB T4 with T04S compressor. Now that the T04Z is available directly from Garrett, there is little reason to rely on 3rd party outfits to cobble this combination together.