Paul,

I just got through reading through John Slades website about
his turbo troubles with different stock and Aussie modified
Mitsubishi turbochargers.

He as well as several other people recommend a Turbonetic
TO4E -50 with the big shaft.  I know the unit  comes with
an Inconel turbine, and P trim is recommended.  Since I want
to turbo normalize the P-ported 13B at high altitude I have
been advised that an A/R   around 1.15.  is best.  This way
the turbine only makes a few inches on sea level take-offs
but really pumps the air at low flight levels.   Do you know
a purchasing source in California?  I am want to make sure
I can order one with high nickel content and ceramic ball
bearings as well.

Doug in Japan

Performance Turbochargers LLC
8482 Cherry Ave.
Fontana, CA 92335
909-429-7200
909-429-7204
Garyhetrick@dieselusa.com
www.dieselusa.com

Limit Engineering
885 Kiowa Ave.
Lake Havasu City, AZ 86403
928-453-7321
928-453-0789 (fax)
craig@redrivernet.com
www.limitengineering.com

Advanced Tuning Products
28988 Hopkins St.
Hayward, CA 94545
510-445-1682
510-445-1692 (fax)
info@atpturbo.com
www.atpturbo.com

Retail Distributors
Jim Wolf Technology
212 Millar Avenue
El Cajon, CA 92020
619-442-0680
619-579-8160(fax)
www.jimwolftechnology.com


You may have trouble buying a new TO4 as it is now obsolete.

The A over R is a measure of how far the inlet diameter is
restricted by the nozzle. An A over R over one means
the inlet gas velocity is actually reduced before it is
applied to the turbine.

The high turbine A/R means it will not generate a lot of turbine HP but
it will be less likely to over rev at high altitude. It will
also have less back pressure on the engine.

There are two A/R's numbers. One for the turbine and one for the
compressor.

http://www.turbobygarrett.com/turbobygarrett/tech_center/gt_basics.html

"GT Basics / Nomenclature

  Please note that we have made
a subtle modification to the GT nomenclature.

In our product catalog, all offerings are grouped according to
their turbine wheel frame size. The frame size of a turbo or CHRA
is dictated by its turbine wheel inducer diameter . The larger
the turbine inducer, the bigger the frame size-- so any turbo
in the GT42 family has a larger turbine wheel inducer than
those in the GT35 family, and so on.

In the model name of each turbo or CHRA, you'll also notice two
digits after the frame size. These two digits refer to the
compressor exducer diameter, as measured in millimeters.

Let's use the GT4294 as an example. This unit has a GT42 frame
size turbine coupled to a 94mm (exducer diameter) compressor wheel.

If there's an "R" on the end of a model name, this means the
unit is ball bearing. So, a GT4294 is not ball bearing; whereas
a GT4294R is ball bearing.

The biggest change related to the nomenclature is this: units
which utilize a 53mm turbine wheel (as measured at the inducer)
are now referred to as "GT25" frame size, while units employing
the slightly larger 53.85mm turbine wheel are now referred to
as "GT28" frame size.

For those familiar with our product range, this means that the
unit formerly known as "the GT28R" (part number 466541-1) is
now in the GT25R family. More specifically, it is now a GT2560R
model."

GTxxyyzz

*  Positions "xx" refers to the frame size of the turbine wheel inducer.

   o For example the "GT28" in "GT2860RS" refers to its turbine wheel
frame size family. All GT28 units use a turbine wheel with 53.85mm [2.12"]
inducer diameter

   o As a rule of thumb, the larger the number, the larger the turbine wheel.


* Positions "yy" designate the compressor wheel exducer (major) diameter
in millimeters

o The "60" in the GT2860RS example above has a 60mm compressor wheel
exducer diameter.

o Note: Wheel sizes 100mm and over omit the "1" (hundreds digit)

o Example: the 02 in a GT4202 refers to its 102mm compressor
wheel exducer diameter


* Positions "zz" may be used to designate special features of a particular turbocharger where applicable

o Example: GT2860RS

o "R" = this is a Ball Bearing unit

o "S" = used for units which require some differentiation
from units in the same family Compare a GT2860R to a GT2860RS.
While both are ball bearing and externally similar, the GT2860RS
is better suited for higher-flow applications than the GT2860R.
In this case, the S reflects the higher-flowing nature of the GT2860RS"

End of Garrett quote.

The 16 pound TO4 I have in my hand as we speak has a turbine inlet area
diameter is roughly two inches in diameter. In the new terminology
the inducers or diameter of the turbine wheel is roughly 3.5 inches
or 90 mm.  It is not out of the housing so I am not sure of
the exact dimensions. It could be a lot smaller. I'll take
it apart shortly when I get time.

The stock 1990 RX7 turbo weighs 22 pounds
but it has a built in waste gate. The stock RX7 1990 turbine OD
is 2.5 inches or 56 mm and compressor OD is 2.4 inches. Compressor
ID is 1.72". This one I have out of the housing. This has been made
to work in a modified form by Dave Leonard and others

The exducer (small diameter of the turbine) size is 2.75
inches in diameter or 70 mm. The turbine A/R is .96.

MY guess is the TO4 turbine is about the same size as a GT4508 or a GT4708.
I could be way wrong as the physical size is a bit bigger.
The GT4508R has a water called bearing like the stock Mazda turbo
and unlike the TO4 so that alone is a big positive. The R stands for
ball bearing. The aerodynamics of these new models has been drastically
improved so I would not be a bit surprised if the GT4508 was more
efficient than the old TO4. One the other hand the turbine is small
relative to the compressor so IMHO I don't think this is what you need.
I would go with a larger turbine to actual reduce the heat load
and the RPM on the turbine. The exhaust gas velocity and mass is
a given so the larger the turbine the lower the RPM.

Garrett uses a small diameter turbine to reduce the rotational inertia
and improve the angular acceleration for automotive use. Not what
a A/C application needs.

The TO4  M-24 compressor has an inlet diameter of 2.5 and an outlet diameter
of 1.95 and the marked A/R is .6.  The compressor wheel OD is roughly 2.5 inches
in diameter and 1.75" small diameter. This size turbo is good for 700 HP
so perhaps you need a higher A/R.

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

Download the catalog and go from there.
http://www.turbobygarrett.com/turbobygarrett/products/catalog.html

What ever you do get one of the these turbo tachs and install it so you
are sure you do not over rev the turbo charger as that is a sure
fire way to have the turbine wheel fail at 1800 F inlet temp.

---------------------------------------------------

I won't need to take my TO4 apart as I just found the TO4 dimensions
in the Garrett cat. Turbine wheel is 74 mm OD and not 90 mm.
That makes the GT3582R a better match and it has a highly
desirable water cooled bearing housing unlike the TO4.

I have also included Jeff Spitzer's spread sheet. Jeff got his
Rotax 914 powered airplane up to 57,000 feet.

One of the things that always bothered me about pressure ratio
calculations is the fact the pressure on the inlet side of the
turbine will vary with turbine RPM. I prefer to look at it
as gas velocity and density input to the turbine.
That can be measured (for awhile until it burns up) with a
tiny pito tube inserted into the exhaust  pipe.

Paul Lamar