Questions about turbos?
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From: Connecticut
Questions about turbos?
I've been reading about turbos over here and have a better understanding about what makes turbos different from each other and how to choose a turbo for differnt applications but I am still a little unclear about a few areas.
1. Surge. How I understand it is when the turbo is compressing too much unusable air. The opposite of choke, when there is not enough airflow. I assume this because when looking at a compressor map they (choke and surge) are on opposite sides of the efficency islands. Other than having a big turbo on a small engine, what causes surge? I guess it sounds like the compressor is "barking"?
2. Trims. I understand that it is a ratio between the inducer and exducer on the compressor and turbine wheels. But I always see 'T trim' or 'P trim' being used injunction with turbos but don't understand that when in that writeup it describes the trims as being a number ie: '56 trim'. For anyone explain this?
1. Surge. How I understand it is when the turbo is compressing too much unusable air. The opposite of choke, when there is not enough airflow. I assume this because when looking at a compressor map they (choke and surge) are on opposite sides of the efficency islands. Other than having a big turbo on a small engine, what causes surge? I guess it sounds like the compressor is "barking"?
2. Trims. I understand that it is a ratio between the inducer and exducer on the compressor and turbine wheels. But I always see 'T trim' or 'P trim' being used injunction with turbos but don't understand that when in that writeup it describes the trims as being a number ie: '56 trim'. For anyone explain this?
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Joined: May 2003
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From: Connecticut
Re: Questions about turbos?
I forgot to add:
3. Tangential. What does this mean? I know it has something to do with how the exhaust gas enters the turbine, but that's it.
4. I also forgot to ask about turbo names. Example: T76GTS, the compressor trim is a 76 to my understanding, but waht does 'GTS' stand for or GT-40 88RL, etc? What does each letter stand for?
3. Tangential. What does this mean? I know it has something to do with how the exhaust gas enters the turbine, but that's it.
4. I also forgot to ask about turbo names. Example: T76GTS, the compressor trim is a 76 to my understanding, but waht does 'GTS' stand for or GT-40 88RL, etc? What does each letter stand for?
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Joined: Mar 2004
Posts: 2,125
From: Connecticut
Re: Questions about turbos?
Garrett Models Explained
GT Models explained
GT Models use a new naming system. The new system was introduced as 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
Digits 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)
B Compressor wheel without nuts
C Ceramic turbine
D A double hole in the turbine housing bypass
E Adapter integrated into the turbine housing
F Carbon seal
G Recirculation Actuator
H Separate manifold adaptor
I Manifold elbow and turbine housing integrated
K Turbo assisted hydraulic
L Body refrigerated by water.
M Manifold and turbine housing integrated
N Imitation shroud wheel
P Variable nozzle turbochargers (VNT OP)
R Ball bearing turbos
S A single hole in the turbine housing bypass
T Titanium-aluminum turbine
V Variable nozzle turbochargers (VNT)
W Refrigerated turbine housing
Z Compact
GT Models explained
GT Models use a new naming system. The new system was introduced as 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
Digits 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)
B Compressor wheel without nuts
C Ceramic turbine
D A double hole in the turbine housing bypass
E Adapter integrated into the turbine housing
F Carbon seal
G Recirculation Actuator
H Separate manifold adaptor
I Manifold elbow and turbine housing integrated
K Turbo assisted hydraulic
L Body refrigerated by water.
M Manifold and turbine housing integrated
N Imitation shroud wheel
P Variable nozzle turbochargers (VNT OP)
R Ball bearing turbos
S A single hole in the turbine housing bypass
T Titanium-aluminum turbine
V Variable nozzle turbochargers (VNT)
W Refrigerated turbine housing
Z Compact
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From: Baton Rouge, LA, USA
Re: Questions about turbos?
Surge is when the pressure at the discharge of the compressor overcomes the compressor wheel and goes backwards for an instant. This depressures the discharge so forward flow re-establishes. Pressure builds up and reverse flow happens again. It happend at low flow rates.
The letter trim designation describes the size of the exhaust wheel. The later in the alphabet, the bigger the wheel. For instance, S is bigger than P. When someone says they have a PT-76GTS, it means that it's a Precision unit (P) based on the old Garret stuff (T), the compressor has a 76mm inducer, it has a new Garret GT series turbine wheel and the exhaust wheel is an S trim. There are lots of ways that turbo model numbers run. TransAm396 is correct on the naming of Garret's new line of turbo's, that always start with "GT". Not sure what a 56 trim is.
There are two types of exhaust turbine entries: tangential and radial. A tangential housing has the exhaust gas entering at an angle, tangentential to the exhaust wheel major diameter. A radial housing has the exhaust gas entry pointing directly at the turbo shaft. The gas has to make an abrupt 90 when it enters before it hits the wheel. This abrupt 90 restricts flow and makes less power.
Mike
The letter trim designation describes the size of the exhaust wheel. The later in the alphabet, the bigger the wheel. For instance, S is bigger than P. When someone says they have a PT-76GTS, it means that it's a Precision unit (P) based on the old Garret stuff (T), the compressor has a 76mm inducer, it has a new Garret GT series turbine wheel and the exhaust wheel is an S trim. There are lots of ways that turbo model numbers run. TransAm396 is correct on the naming of Garret's new line of turbo's, that always start with "GT". Not sure what a 56 trim is.
There are two types of exhaust turbine entries: tangential and radial. A tangential housing has the exhaust gas entering at an angle, tangentential to the exhaust wheel major diameter. A radial housing has the exhaust gas entry pointing directly at the turbo shaft. The gas has to make an abrupt 90 when it enters before it hits the wheel. This abrupt 90 restricts flow and makes less power.
Mike
Registered User
Joined: Mar 2004
Posts: 2,125
From: Connecticut
Re: Questions about turbos?
i got that off jose's website.
Originally Posted by engineermike
Surge is when the pressure at the discharge of the compressor overcomes the compressor wheel and goes backwards for an instant. This depressures the discharge so forward flow re-establishes. Pressure builds up and reverse flow happens again. It happend at low flow rates.
The letter trim designation describes the size of the exhaust wheel. The later in the alphabet, the bigger the wheel. For instance, S is bigger than P. When someone says they have a PT-76GTS, it means that it's a Precision unit (P) based on the old Garret stuff (T), the compressor has a 76mm inducer, it has a new Garret GT series turbine wheel and the exhaust wheel is an S trim. There are lots of ways that turbo model numbers run. TransAm396 is correct on the naming of Garret's new line of turbo's, that always start with "GT". Not sure what a 56 trim is.
There are two types of exhaust turbine entries: tangential and radial. A tangential housing has the exhaust gas entering at an angle, tangentential to the exhaust wheel major diameter. A radial housing has the exhaust gas entry pointing directly at the turbo shaft. The gas has to make an abrupt 90 when it enters before it hits the wheel. This abrupt 90 restricts flow and makes less power.
Mike
The letter trim designation describes the size of the exhaust wheel. The later in the alphabet, the bigger the wheel. For instance, S is bigger than P. When someone says they have a PT-76GTS, it means that it's a Precision unit (P) based on the old Garret stuff (T), the compressor has a 76mm inducer, it has a new Garret GT series turbine wheel and the exhaust wheel is an S trim. There are lots of ways that turbo model numbers run. TransAm396 is correct on the naming of Garret's new line of turbo's, that always start with "GT". Not sure what a 56 trim is.
There are two types of exhaust turbine entries: tangential and radial. A tangential housing has the exhaust gas entering at an angle, tangentential to the exhaust wheel major diameter. A radial housing has the exhaust gas entry pointing directly at the turbo shaft. The gas has to make an abrupt 90 when it enters before it hits the wheel. This abrupt 90 restricts flow and makes less power.
Mike
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