turbosocks

So, i have been doing quite a bit of research lately, to find a turbo for my SRT-4, and I learned a few things, and thought I should post up some more advanced turbo information for people wanting to just know, or pick the EXACT turbo for their setup.

<span style="font-size:12pt;line-height:100%">Lets first go over A/R ratios.
</span>
Small displacement engines, a smaller A/R is better due to the lower amount of exhaust volume.

Larger Displacement engines, a bigger A/R is better due to the higher exhaust volume than a small displacement engine.

Although, sometimes you will WANT some lag, so you spool a little later. In this case, you would want to go with a bigger A/R even if you have a smaller displacement engine. In the case of my car, I will be getting a bigger A/R on both the compressor and turbine housings so I have a bit of lag

Another good rule of thumb for A/R sizing: smaller A/R housing = lower powerband, bigger A/R housing = higher powerband

Here is also a good way to look at it, in terms of water that I got off another site:

Imagine if you have a garden hose spraying water out at a pinwheel
with the hose open ended, the pinwheel spins okay. Put a nozzle on it an the pinwheel will spin like mad.

There are issues with the nozzle on the end, you lose volume but gain pressure. With the nozzle off you gain volume, but lose pressure and you can't turn the pinwheel as much.

so if you have a smaller A/R the pinwheel would 'spool up' faster but lack volume.

Here is a graphic that shows how to measure the A/R, although, its usually listed on the turbo. A/R doesn't have anything to do really with 'trim'


i will try and redo this graphic since its barely legible.

<span style="font-size:12pt;line-height:100%">Now onto Trim, what it means, how to calculate it, etc.</span>

Again, if you have a small displacement engine and want your car to spool really fast, a smaller trim would be optimal. Bigger displacement, where you want a higher cfm, bigger trim is the way to go.

Heres a quick breakdown of what you will need to figure out the trim.


We will get back to that in a minute...

<u>What is an Inducer?</u>
The inducer is the smaller diameter of the compressor wheel and the bigger diameter of the turbine wheel.

This part of the wheel has the most effect on airflow. With a bigger inducer, your turbo will flow more air. With a smaller inducer, it will flow less air. Flowing more air = more power.

The downside to a bigger inducer is lag (if you consider lag a downside) and a possibility of surge.

Here is a comparison of compressor wheels with different sized inducers, with same sized exducers.



<u>What is an Exducer?</u>
The exducer is the bigger diameter of the compressor wheel and the smaller diameter of the turbine wheel.

This part of the wheel has the most effect on spool. With a bigger exducer, you turbo will spool faster. with a smaller exducer, it will spool slower.


Here is a comparison of compressor wheels with different sized exducers, with same sized inducers.


<u>What is Surge?</u>
Simply, something you never want to see happen.

Surge is the situation when the compressor "spits out" more air than the engine can swallow, which causes a backup of air at the intake and it actually creates reverse-flowing pressure waves that can be very damaging to the turbo.

<span style="font-size:12pt;line-height:100%"><u>Now to the good stuff, lets put this information to use to figure out trims!!! so much fun.</u></span>

Figuring out the trim of a wheel (compressor or turbine)

There is a very simple formula to figure out compressor wheel trim.


the formula is OPPOSITE to figure out turbine wheel trim.. its ALWAYS minor dia. / major dia.

for example a T3/T4E 50 trim has a inducer wheel diameter of 2.122" and exducer wheel of 3.00" (compressor)

2.122 x 2.122 = 4.503
3.000 x 3.000 = 9

4.503/9.000 = .5003 X 100 = 50 trim

For the most part, when you see turbos listed, the 'trim' is always compressor since its most important when selecting a turbo size.

For the Turbine side, the wheels are most often referred to is Stages. Most common are Stage 1, Stage 2 and Stage 3 trim wheels. Exhaust/Turbine side isn't AS important. Typically you want the smaller wheel for faster spool, but for higher power, the bigger wheels will have less restriction and less backpressure in the exhaust.

<u>A common mishap when people are looking at turbos is when they are looking at different 'families' of turbo with the same trim, and thinking they have the same wheel.. They don't, by far.</u>

A t3 60 trim has a compressor wheel with these specs: 1.83"IN/2.367"EX
A t3/t4b 60-1 has a compressor wheel with these specs: 2.324"IN/3.0"EX
A t3/t4e 60 trim has a compressor wheel with these specs: 2.290"IN/2.95"EX

Now, you might be thinking... the T4B and T4E have about the same size wheels.. you are partially correct. but the T4B will flow MUCH more, because the 'B' housing wheels have a higher blade height.

and the t3 60 trim obviously is MUCH smaller than either of the other turbos.


That about covers A/R, Trim, and some of the more advanced concepts when looking at a turbo. I will be adding more info to this as I write it up.

Here is a List of some information I have collected, relating to popular turbos out there and the sizes that are most common for A/R, Trim, etc.


<u>Mitsubishi Turbos and 'breakdowns'</u>
TD05HR-16G-9.8cm^2
TDO5= Turbine housing size
H = type of blade
R = reverse rotation
16G = Compressor housing size
9.8cm^2 = A/R measurement

TD04 housing = 1.81"
TD05 housing = 2.22"

Mitsubishi 16G6 (EVO. VIII wheel)
Inducer: 1.89”
Exducer: 2.68”

Mitsubishi 20G-R
Inducer: 2.04”
Exducer: 2.67”



<u>Garrett Turbos and 'breakdowns</u>
T3/T4E 50 trim
T3 = Turbine housing size
T4 = Compressor housing size
E = Compressor housing sub-family
50 trim = Trim of Compressor wheel

GT3076RS
GT = refers to turbo family
30 = turbine exducer measurement
76 = compressor exducer measurement
R = ball bearing
S = higher flowing turbo assemlby

turbine T3 = 2.32"
turbine T4 = 2.92"
turbine GT28 = 2.10”
turbine GT28 = 2.20”
turbine GT30 = 2.36”
turbine GT35 = 2.68”
turbine GT40 = 3.03”
turbine GT42 = 3.23”

Garrett T3 35trim
Inducer: 1.396”
Exducer: 2.367”

Garrett T3 40trim
Inducer: 1.484”
Exducer: 2.367”

Garrett T3 45trim
Inducer: 1.595”
Exducer: 2.367”

Garrett T3 50trim
Inducer: 1.674”
Exducer: 2.367”

Garrett T3 60trim
Inducer: 1.830”
Exducer: 2.367”

Garrett T3 super 60
Inducer: 1.900”
Exducer: 2.367”


Garrett T3/T4B 40trim
Inducer: 1.870”
Exducer: 2.950”

Garrett T3/T4B 50trim
Inducer: 2.122”
Exducer: 3.000”

Garrett T3/T4B 60-1
Inducer: 2.324”
Exducer: 3.000”


Garrett T3/T4E 50trim
Inducer: 2.122”
Exducer: 3.000”

Garrett T3/T4E 54trim
Inducer: 2.170”
Exducer: 2.950”

Garrett T3/T4E 57trim
Inducer: 2.230”
Exducer: 2.950”

Garrett T3/T4E 60trim
Inducer: 2.290”
Exducer: 2.950”

Garrett GT3147RS
Inducer: 2.03”
Exducer: 2.67”

Garrett GT3071RS
Inducer: 1.77”
Exducer: 2.80”

Garrett GT3076RS
Inducer: 2.23”
Exducer: 2.99”

Garrett GT3082RS
Inducer: 2.42”
Exducer: 3.23”

Garrett GT3582RS
Inducer: 2.42”
Exducer: 3.23