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Turbo Introduction

Time:2012-04-06 15:01Turbochargers information Click:

Turbo Introduction

The so called "T-series': T60, T61, T66, T70, T72, T76... are T4 turbos as well. The number means the compressor inducer size. ie: T76 means it has 76mm compressor inducer.

GT30R is a hybrid of GT30 turbine mated to 56 trim GT37 compressor. 

Wheel "trim" refers to the squared ratio of the smaller diameter divided by the larger diameter times 100. Generally, the larger the trim number the more flow the wheel has.

Garrett Turbos:

Garrett GT series turbo

For "families" of turbine wheels (those with the same inducer diameter), larger trim usually means better flow with less backpressure but longer spool time. 

GT37 Turbo Dimensions

GT28RS is a hybrid of GT28 turbine mated to 62 trim GT30 compressor.

Garrett ball bearing GTx-R turbo


There're two commonly used types of turbos, Mitsubishi and Garrett turbos. There are others but as not common...such as IHI, KKK turbos

Mitsu and Garrett turbos have totally different designations.

HKS uses Garrett turbos. HKS GT series turbos use Garrett GT's turbine with GT's compressor. For example, HKS GT 2835 is GT28  turbine with GT35 52 trim compressor.



Mitsubishi uses TD04, TD05, TD06, ...to designates turbo housing.

A/R is a ratio of the exhaust discharge area vs the distance from the center of turbine wheel to the center of the cross sectional area. Smaller A/R housing has faster spool up. Bigger A/R housing has less back pressure, more flow for the top end.

Greddy modifies Mitsu turbos. I don't have any published specs for Greddy turbos and i have not taken any time to measure them. It's possible some of turbos have different specs from Mistubishi. Also, both Greddy TD05 and TD06 use 3 bolt turbine flange where as Mistubishi's uses 4 bolt flanges.

Bisides the TD04, TD05, TD06, TD07 and TD08 turbos, Greddy also makes hybrid turbo, T67 is TD07 compressor and TD06 turbine, same turbo as TD06SH-25G. T78 is the compressor of TD08 and turbine of TD07, T88 uses compressor and turbine from TD08.


  • TD05 turbine housing with 'H' style turbine wheel. There are S, SH, H... style of turbine wheel/housing. 

  • T family has T22, T25, T3, T350, To4B, To4E, TS04, To4R ...These are 50 year old, WWII generation turbos.

    Mitsu turbos:

    It's a Garrett ball bearing GT turbo. It has 76mm compressor wheel, 60mm turbine wheel (same size as 3037).

    I'm working on spec'ing a newer turbo, GT30R. It's smaller than 3037 physically, but it flows quite a bit more and more efficient than 3037.


    The newer line of Garrett GT-R turbos are hybrid turbos. For example, 

    Garrett basically has two lines of turbos. The ancient, inefficient T series turbos and the new, modern, ball bearing GT series turbos.


  • 8cm^2 is referring to exhaust discharge area in the turbine housing. More specifically, it is the smallest cross-sectional area of the scroll, turbine housing. Very similar to Garrett turbo's A/R. The smaller number means faster spool-up but more back pressure at higher rpm. Bigger number means longer spool up but less back pressure, thus more top end power.

  • 16G compressor wheel. 16 is the size of the wheel, 1.83 inducer, 2.37 exducer. There is no direct correlation between MHI designation and actual physical size of the compressor wheel. G is the style of wheel (uneven height of blades). C, B, T style wheel's blades have the same height. Blades are equally spaced, but the number and pitch of the blades vary between models. 

    60mm UHP turbine wheel, T3 inlet flange, 4" outlet, .82 a/r.


    GT3037 is a hybrid of GT37 52 trim compressor and GT30 turbine.

  • The newer line of GT turbos are ball bearing on journal and thrust bearing. The turbine and compressor wheels are improvely aerodynamically to flow more air. GT20, GT22, GT25, GT30, GT35, GT40, GT45, ... GT turbos produce slightly more hp then older T series turbos with the same number designation. A GT Garrett turbine wheel wil flow more air than similar sized Greddy turbine wheel. Thus GT turbos are able to boost higher and flow more.

    GT35 Dimensions

    For example, TD05H-16G 7cm^2 is a turbo with,

  • Turbonetics and many domestic makers turbos based on T series turbos. A T3/To4E 60 T .63A/R is a hybrid turbo with T3 turbine, To4E compressor, 60 Trim compressor wheel and .63 A/R turbine housing.


    76mm BCI-18 compressor wheel, 4" inlet, 2.5" outlet

    For compressor wheels , larger trim tends to mean slightly lower efficiency.

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