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Turbo class
101
How to read
Garrett Turbos:
GT Models explained
GT Models use a new naming
system. The new system was introduced to permit an easier
identification of the turbo's characteristics.
New models can have up to 10
digits, that specify its range, measurement of the compressor
wheels and the rest of the turbo's characteristics. The old
naming system is obsolete.
|
Example |
G |
T |
3 |
2 |
7 |
1 |
B |
F |
|
Digits |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
Dígits Used
|
1-2 |
Should always be GT |
|
3-4 |
Range denomination ( based on the size of the turbine
wheels and the turbine housing) |
|
5-6 |
Corresponds to the diameter of the compressor wheel in mm
( In the event that the wheel is bigger than 100mm only
the last two figures are used ) |
|
7-10 |
These are used to designate the specific characteristics
of each model, according to the following table: |
|
A |
Variable nozzle turbochargers
(VAT) |
N |
Imitation shroud wheel |
|
B |
Compressor wheel without nuts |
O |
|
|
C |
Ceramic turbine |
P |
Variable nozzle turbochargers
(VNT OP) |
|
D |
A double hole in the turbine
housing bypass |
Q |
|
|
E |
Adapter integrated into the
turbine housing |
R |
Ball bearing turbos |
|
F |
Carbon seal |
S |
A single hole in the turbine
housing bypass |
|
G |
Recirculation Actuator
|
T |
Titanium-aluminum turbine |
|
H |
Separate manifold adaptor |
U |
|
|
I |
Manifold elbow and turbine
housing integrated |
V |
Variable nozzle turbochargers
(VNT) |
|
J |
|
W |
Refrigerated turbine housing |
|
K |
Turbo assisted hydraulic |
X |
|
|
L |
Body refrigerated by water. |
Y |
|
|
M |
Manifold and turbine housing
integrated |
Z |
Compact |
Click for
Complete Master List of Garrett Turbos
What is an A/R
ratio and how is it calculated?:
The A/R in a relationship that
is obtained when dividing the interior area of the turbine
where the inner walls are found, through the turbine housing
radio from the center to the tongue as the illustration
indicates.
A/R values are expressed as
.35, .47, .68, .84, 1.00, 1.15, etc.
A small A/R indicates a small
interior volume in the small turbine and a large A/R indicates
a greater volume.
At a minimum A/R the motor's
response is produced at small revolutions per minute but at
high revolutions we will not achieve an adequate caudal. We
should always find a compromise between achieving the lowest
response possible and have enough caudal at high revolutions.
The picture below is for reference:
What is the
Trim of a turbo and how is it calculated?
Each turbine wheel y compressor
wheel model generally have the same turbine diameter (highest
diameter), but different steps (lowest diameter). Each type of
step (trim), has different blowing characteristics.
- TRIM values are expressed as
45, 50, 55, etc... and can only go from 0 to 100. A value of
100 means Dp = Dg
- A large TRIM indicates a
large turbine diameter.
- A TRIM of 55, gives 10% more
caudal than a TRIM of 50.
- TRIM is used in the same way
for turbine wheels as for compressor wheels.
- TRIM is calculated through
the following formula.
TRIM = ( Dp / Dg )˛ x 100
Si Dg = 50 mm y Dp = 35 mm
TRIM = ( 35/50 )˛ x 100 = 49
What are the
different flanges and what are the sizes?
- All most all of your turbo
head units come with the flanges described below. The T3
housing is the smallest and flows the least, with the
T6/Thumper flange being the biggest and flowing the most.
The flange plays a role in spool up, backpressure...etc.
The rule of thumb here is use the largest flange you can
possibly fit. Of course this will be limited by what
headers you use, since most are pre-fabbed and come with a
flange already, and under hood space will also be a
limitation.
Selecting a Turbo for your Engine 101
Which turbo for
me?
-
First you must
select a Horsepower goal. This is the first parameter you
need, to start doing the elimination process to reach your
goal.
-
Second, what
rpm range or max rpm range are you shooting for?
-
Third what
boost pressure are you looking to run?
-
And lastly,
how much room do I have?
Below we will
explain what is needed to select a turbo and how to do it
using a theoretical setup. Not all details are covered since
their are millions of different configurations, such as cam
selection, head selection...etc. Keep in mind the internal
combustion engine is still nothing more then mechanical air
pump. So these calculations will get you VERY close to what
you will need. They will also teach you how to read a
compressor map as well as understand the physics of choosing
a turbo.
| PSI |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
| rpm\PR |
1.00 |
1.07 |
1.14 |
1.20 |
1.27 |
1.34 |
1.41 |
1.48 |
1.54 |
1.61 |
1.68 |
1.75 |
1.82 |
1.88 |
1.95 |
2.02 |
2.09 |
2.16 |
2.22 |
2.29 |
2.36 |
| 3400 |
23 |
24 |
26 |
27 |
29 |
30 |
32 |
33 |
35 |
37 |
38 |
40 |
41 |
43 |
44 |
46 |
47 |
49 |
50 |
52 |
54 |
| 3500 |
23 |
25 |
27 |
28 |
30 |
31 |
33 |
34 |
36 |
38 |
39 |
41 |
42 |
44 |
46 |
47 |
49 |
50 |
52 |
54 |
55 |
| 3600 |
24 |
26 |
27 |
29 |
31 |
32 |
34 |
35 |
37 |
39 |
40 |
42 |
44 |
45 |
47 |
49 |
50 |
52 |
53 |
55 |
57 |
| 3700 |
25 |
26 |
28 |
30 |
31 |
33 |
35 |
36 |
38 |
40 |
41 |
43 |
45 |
47 |
48 |
50 |
52 |
53 |
55 |
57 |
58 |
| 3800 |
25 |
27 |
29 |
31 |
32 |
34 |
36 |
37 |
39 |
41 |
43 |
44 |
46 |
48 |
49 |
51 |
53 |
55 |
56 |
58 |
60 |
| 3900 |
26 |
28 |
30 |
31 |
33 |
35 |
37 |
38 |
40 |
42 |
44 |
45 |
47 |
49 |
51 |
53 |
54 |
56 |
58 |
60 |
61 |
| 4000 |
27 |
28 |
30 |
32 |
34 |
36 |
38 |
39 |
41 |
43 |
45 |
47 |
48 |
50 |
52 |
54 |
56 |
58 |
59 |
61 |
63 |
| 4100 |
27 |
29 |
31 |
33 |
35 |
37 |
39 |
40 |
42 |
44 |
46 |
48 |
50 |
52 |
53 |
55 |
57 |
59 |
61 |
63 |
65 |
| 4200 |
28 |
30 |
32 |
34 |
36 |
38 |
39 |
41 |
43 |
45 |
47 |
49 |
51 |
53 |
55 |
57 |
59 |
60 |
62 |
64 |
66 |
| 4300 |
29 |
31 |
33 |
35 |
36 |
38 |
40 |
42 |
44 |
46 |
48 |
50 |
52 |
54 |
56 |
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