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Old 02-24-2009, 09:26 PM   #1
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Turbo codes for Garrett + Precision Turbos

Obtained from posted by DIRep972 AKA Chris Stein

Hopefully it helps. Frankly, the turbo code and models confused me until I read this post. Enjoy!

I still see alot of people confused on the Garrett GT model #'s and especially the Precision models #'s that use the GT series parts. Im going to try and explain the part #’s so everyone can understand whats going on inside the turbos that we use here on H-T on a daily basis. I am going to start with the Garrett GT series and then explain the Precision SC/PT/GT line up.
The basic GT model code format is: GTaabbcccc

The first two positions are always GT.

Position "aa" tells you the turbine family and bearing system(does not mean ball-bearing) that the turbo uses. Position "aa" is considered the base model # and is often used as a shorthand name for the turbo.

Position "bb" tells you the compressor wheel family the turbo uses.

Position "cccc" is used to tell you special features of a specific turbocharger. Not all four positions are always used. Here are a few of the codes used(the only ones we really deal with):

L- Watercooled center housing
R- Ball bearing
S- Internally wastegated

After the model code you can list specific wheel trims of the wheel family's and designate the housings.

Here is an example of how these codes are used and often mixed up:

"GT35R"- this is a base part # in short hand. There are many variables of this turbo.

The "GT3540R" is most often the turbo that the "GT35R” short hand part # refers too. To designate the exact specs on this turbo you would specify the family and trim and call it a "GT3540R 56 trim"

Another variable of this turbo would be a "GT3540." Notice there is no "R," this means it is not ball bearing.

It is a good idea to designate the specs for the wheel that you are refering too in the part #. An example is a "GT3540 56 trim" and "GT3540 54 trim" This lets you know exactly what wheel from the GT40 family the turbo is using. The 56 trim GT40 wheel uses a 82mm exducer while the 54 trim GT40 wheel uses an 88mm exducer. If there are two wheels in the same family with the same trim you should then clarify the exducer spec.

Another variable of this turbo is the "GT3040R" Notice the change in the "aa" part of the code. This tells you the turbo is using the GT30 family turbine wheel/bearing system. In short hand this turbo would be referred to as a GT30R. (Alot of people will like to call it a GT35R and then say it has the GT30 turbine side. That is not correct. What they are trying to do when they refer to it in that way is to tell you that it is using the GT40 compressor wheel that comes in the "GT35R.”

Are you guys starting to see why there are so many misconceptions and false information going around about these turbos?

It gets even more confusing when you start mix and matching these GT wheels with T/E/B series wheels, E/S compressor housings, and 5 bolt turbine housings.. This is what happens when Precision comes into the picture.

Precision manufactures Garrett performance turbos. This means they use Garrett wheels and CHRA’s and make their own custom housings, upgrade the bearing systems, and provide their own full custom line up of turbos with their own nomenclature. By now most of us have already memorized the Precision naming system(or lack of naming system, its very confusing) for the SC line up of turbos. Now we need to learn the GT line up of precision turbos and how they name them when they mix and match them with GT parts.

The format I use for Precision turbos is: XXYY

Below are the codes used in the "XX" spot.

SC- (stands for Sport Compact) These are T3/T4 hybrid turbos that use standard T series bearing systems.
PT- (stands for Precision Turbo. duh.) These are strait T4 turbos that use standard T series beaing systems.
GT- These turbos use Garrett GT turbine wheels/bearing systems and they can be T3/T4’s or strait T4’s.
(Sometimes the SC line up and PT line up cross paths, like when you put an SC61 in a T4 turbine housing it now becomes a PT61. Easy enough to understand.)

The "YY" spot is used to tell what compressor wheel the turbo is using.

When refering to the T family of compressor wheels the "YY" code tells you the size of the inducer on the compressor wheel.
Example’s: “PT67" and “PT70”- The PT67 has a compressor wheel with a 67mm inducer and the PT70 has a compressor wheel with a 70mm inducer.
To determine the turbine wheel being used you must specify this after stating the turbos name along with the compressor housing and turbine housing A/R you want as well. A “PT67 w/ T350 76 trim w/ .70ar compressor housing and .68A/R turbine housing” is an example of doing this.

When refering to E family compressor wheels the “YY” code tells you the trim of the wheel. The only wheel that directly represents it’s trim # is the 50 trim found in the SC50. The other wheel trim’s have desginated #’s that represent the trim #. For example, an SC34, uses a 57 trim E family compressor wheel and an SC32 uses a 54 trim E family compressor wheel. (Why they use those #’s to represent the trim I have no idea and as far as I can tell it is not a predictable system and you must memorize it.) All E family compressor wheels are mated with T31 turbine wheels.

When refering to B family compressor wheels,(well we actually only use one of them) the “YY” code tells you the compressor wheel its using and also the turbine wheel. The only B family wheel we use is the 60-1 compressor wheel and it is found in the SC52,53,54, and 60. Each of these turbos uses a different turbine wheel and precision assigns each one of these #’s to represent a different turbine wheel while the compressor wheel stays the same for all of these turbos. For example an SC60 uses a 60-1 compressor wheel with a T31 turbine wheel and an SC52 uses the same 60-1 compressor wheel but with a T350 76 trim turbine wheel. With these #’s you do not have to state the turbine wheel being used but you do need to state the housings.

Now lets mix them up with GT series parts and get confused.

When Precision uses standard T series bearing systems with T series turbine wheels the SC/PT part # coding is used. When they put a GT series compressor wheel in a turbo and still use a standard T series turbine wheel/bearing system they go by the code for the T series parts. In the T series coding the “YY” spot is designated for specifying the compressor wheel inducer. An example of this type of turbo is the “SC61.” The “SC61” has a T series turbine wheel/bearing system and uses the GT40 56 trim compressor wheel that has a 61mm inducer. (As far as I know the GT40 56 trim is the only official GT wheel that precision is mating with standard T series turbine sides and bearing systems. The 67mm 63 trim compressor wheel found in the PT67 is not officially a GT family wheel, although it was designed around the same time, it is designated a Garrett Performance wheel and was originally designed for use by HKS in the T04R.)

When they switch over to GT series turbine wheels and bearing systems is when they switch over to the GT series part # code.

The GT series code for Precision is:
The first two positions tell you its a GT series turbo.
The “aa” positions tell you which turbine wheel family and bearing system it is using.
The “Z” position tells you which compressor housing it comes with. (I think they specify this because the Garrett GT stuff all comes with “S” compressor housing standard while the Precision stuff comes standard with “E” compressor housing standard. “S” housings are available as an option.)

To specify Ball Bearing just add BB after the short hand part code.

Precision leaves their names in shorthand and does not specify which compressor wheel is being mated with the “GTaa” turbine/bearing set up. It is assumed in most cases, like in the case of the GT35e. The GT35e turbo comes with the GT40 56 trim compressor wheel(this is also used in the SC61 and has a 61mm inducer.) I have seen Precision etch GT3561e into these turbos so I like to refer to it in that way so that there is no confusion.

Precision offers the 5 bolt (TA31) turbine housing standard with the “GT” line up but the 4 bolt is an option. Ball Bearing is also an option that you can upgrade too. (you do get the GT ball bearing system if you order a GT series turbo. remember it comes w/ a GT bearing system. However if you order an SC61 ball bearing w/ out the GT turbine side you will get a standard T series ball bearing set up.)

Hope that clears up some confusion and doesn't add too much more. There are alot of #'s and symbols so its takes some time of seeing it over and over again before it soaks in. I left out alot but I tried to put everything in their that I felt was pertenant to the turbos we actually use in the honda world. If anything is wrong let me know and I will correct it.

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