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Model Years 1999.5 - 2003 7.3L PowerStroke
Engine
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The GTP38R Turbo
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A Garrett Exclusive Ball Bearing Cartridge for
Unbeatable Response, Efficiency, and Durability. Elimination of the Thrust
Bearing Eliminates Failures at Elevated Boost Levels
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The 88mm GT Compressor Wheel Provides 33% More
Flow than the Stock 80mm Wheel. Ported Shroud Housing Improves Compressor Flow
Range for Surge Control
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1.00 A/R Turbine Housing for Free Flowing
Exhaust with Reduced Back Pressure and up to 200° F Reduction in Exhaust Gas
Temperature
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Maximum Recommended Boost Level is 40psi
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Turbo Glossary-
Performance
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A/R describes a geometric property of all compressor and turbine
housings. Increasing compressor A/R optimizes the performance for low
boost applications. Changing turbine A/R has many effects. By going to a
larger turbine A/R, the turbo comes up on boost at a higher engine
speed, the flow capacity of the turbine is increased and less flow is
wastegated, there is less engine backpressure, and engine volumetric
efficiency is increased resulting in more overall power.
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The CHRA includes a complete turbocharger minus
the compressor and turbine housings. |
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When an angle is machined on the turbine wheel
exducer (outlet side), the wheel is said to be ‘clipped’. Clipping
causes a minor increase in the wheel’s flow capability, however, it
dramatically lowers the turbo efficiency. This reduction causes the
turbo to come up on boost at a later engine speed (increased turbo lag).
High performance applications should never use a clipped turbine wheel.
All Garrett GT turbos use modern unclipped turbine wheels.
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The GT designation refers to Garrett’s state-of-the-art turbocharger
line. All GT turbos use modern compressor and turbine aerodynamics which
represent huge efficiency improvements over the old T2, T3, T3/T4, T04
products. The net result is increased durability, higher boost, and more
engine power over the older product line. |
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On-center turbine housings refer to an outdated style of turbine housing
with a centered turbine inlet pad. The inlet pad is centered on the
turbo’s axis of rotation instead of being tangentially located. Using an
on-center housing will significantly lower the turbine’s efficiency.
This results in increased turbo lag, more backpressure, lower engine
volumetric efficiency, and less overall engine power. No Garrett OEM’s
use on-center housings.
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Trim is an area ratio used to describe both turbine and compressor
wheels. Trim is calculated using the inducer and exducer diameters. As
trim is increased, the wheel can support more air/gas flow. Use these
formulas when calculating trim:
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A wastegated turbocharger includes an integral device to limit turbo
boost. This consists of a pneumatic actuator connected to a valve
assembly mounted inside the turbine housing. By connecting the pneumatic
actuator to boost pressure, the turbo is able to limit its maximum boost
output. The net result is increased durability, quicker time to boost,
and adjustability of boost. |
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