Hello all,

In trying to educate myself more about turbo technology, I'm quickly realizing that when looking at vendors offerings, that saying GT35R for example, really only tells you just a small part of the whole story.

In this thread, I thought I might be able to solicit members to contribute information which we know about the turbo options out there right now, their specifications, and other results, opinions, etc.

All participants should have a handle on the concepts summarized here:

http://www.turbobygarrett.com/turbob...ch_center.html

Here are some questions that I had.

1. What is the history of this T3, T3/4, T4 turbine housing designation? Is it Garrett specific? Is there T2 and T5? What specifically does it dictate? The size of the flange on the turbine inlet?

2. I notice Full Race uses a GT35 turbo for both their Stage 3 and 4 kits. Is it common that from any vendor like Buschur, AMS, Full-Race that you can specifiy your Garrett turbo to any turbine side trim and A/R plus specifiy the compressor side to anything you want?

3. What options apart from Garret turbos exist out there? The GT37 that people talk about... is this a Garrett item? Could someone explain more about this turbo and how it can be specified? I thought it was made perhaps by Precision Turbo?

4. Where does twin-scroll play a role in all this? Does the turbo for example in Garrett's case need to be manufactured as twin-scroll from the beginning? Am I correct in saying the GT30 and GT40 and GT42 turbos by Garrett are twin scroll? Whike the GT35 is not?

So just some basic questions to start, but I invite any discussion that helps explain further the turbo options available to us evo owners.

T2's are the Garrett T25 and T28 turbos. Biggest "t" size I've heard of is a GT47R

1) There is T2, T3, T4 and T6

2) it is ok for you to specify what you want from Full-Race i can not say anything for the other vendors

3) The GT37 is a precision turbo. It is not a true GT turbo however, so the name GT37 (which i think AMS started naming them??) is not a correct name

4) twinscroll makes any turbo spool faster, respond quicker, and increases turbocharger efficiency. Some turbos are available as twinscroll (40R, 42R, 45R) others must be modified to be twinscroll (30R, 35R)

T2, T3,T4, T5, and T6 are all Garrett nomenclature and specifically refer to their turbos. The GT series is something new, but the base designs of most all of these turbos has been around since like, the 50's. They started out (and are still used) on diesel trucks and tractors maybe some trains.

There are a tremendous amount of combinations you can make by mixing and matching different compressor housings with differet turbine housings with different inlets, different wheels and different center sections. ITs just that the sport compact industry has narrowed a lot of them down to very common, popular applications depending on wether you have a ~1.6L, ~2.0L, or ~3.0L engine or so on. That's pretty much why a T4 is as big is as you are likely to see.

T6 is not Garrett nomenclature. T2 is actually T25.

T2, T3,T4, T5, and T6 are simply flange sizes for the turbine inlet, T2 being the smallest (in area) and T6 being the largest. T3 is by far the most popular flange used today on sport compact cars.

Thanks guys good info so far.

So how about who the players are in the market as it relates to Evo's?

Garrett, Precision Turbo, Turbonetics, Greddy?

Who else is out there?

Presumably Garrett turbos are 100% built and designed by Garrett. Is this true of the other companies?

Do these other companies use the Garrett standard of Tx turbine inlet design?

I recall hearing something about how the twin scroll GT30's are created. Like a company makes the twin scroll housing for replacement to a Garrett GT30 turbo? What company again does this?

Also there exists companies like Forced Performance who modify turbos. Does Forced Performance create their own turbos as well or just do modifications?

In terms of the modifications they make, is it confined to porting and modifying existing turbos, or do they develop new components from scratch like wheels/turbines?

Here is a GT55 It uses the T6 housing..

http://www.atpturbo.com/Merchant2/me...egory_Code=GLF

I'm not positive about this but I think the twin scroll turbo chargers need new exhaust turbine wheels so one exhaust flow can hit an area for faster spool while the other hits another part of the fin for same/better top end. Does anyone know if this is correct?

Garrett, Mitsubishi, KKK, and IHI are pretty much the only people left that actually MAKE turbos from scratch. There are/were other companies like Borg-Warner, Hitachi, and some other I can't remember too, but a lot of them were bought out by Honeywell which owns Garrett AiResearch. Mitsubishi Heavy Industries and Garrett cover most of the market and most OEM turbos come from them.

Companies like GReddy, HKS, Turbonectics actually take the above companies designs and modify them as their own.

GReddy modifies Mitsubishis
HKS modifies Garretts
Turbonetics modifes Garretts.

dont forget about the vcariable geometry turbo, said to help decrease lag and increase power across the spectrum

Great info!

Garrett does not produce twin-scroll GT35R but Turbonetics does... does that mean Turbonetics casts a special turbine housing on their own?

Another question... why have I never heard of an Evo running a Turbonetics turbo?

And can someone explain to me.. the GT37R or I think what is called T67 P-Trim...

I believe this is a turbo from a company called Precision Turbo?

How specifically is this turbo developed? What is it derived from?

Precision turbo has a lot of clout in the tuner world because they have the ability to cast their own turbine housings and inlets which lets them adapt Garrett style turbos in bolt on Ford and Mitsubishi applications. They fine tune winning combinations that make fast drag cars as opposed to a turbo better suited for a diesel dump truck.