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 The old naming system is obsolete.
[font=Arial]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.
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[font=Arial]TRIM values are expressed as 45, 50, 55, etc… and can only go from 0 to 100. A value of 100 means Dp = Dg [/font][font=Arial]A large TRIM indicates a large turbine diameter. [/font][font=Arial]A TRIM of 55, gives 10% more caudal than a TRIM of 50. [/font][font=Arial]TRIM is used in the same way for turbine wheels as for compressor wheels. [/font][font=Arial]TRIM is calculated through the following formula. [/font]
[font=Arial]TRIM = ( Dp / Dg )² x 100
Si Dg = 50 mm y Dp = 35 mm
TRIM = ( 35/50 )² x 100 = 49
[left]What are the different flanges and what are the sizes?[/left]
[/font][font=Arial]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.[/font]
[font=Arial]Basic T3[/font]
[font=Arial]Basic T4[/font]
[font=Arial]Basic T6[/font]
[left]the following was ripped from http://forcedinductions.com/help.htm[/left]
