can somebody explain turbos to me?

[vsp3c]

before you guys call me a nub and flame me to ashes, i know how they work :p

i was just wondering if somebody could teach me about compressor trims and exhaust a/r...and how they relate to the amount of power they could make and spool up time ( let's pretend we're working with a 2liter engine..sr/rb20det ) if somebody could explian compressor maps to me, that would be great too ( i've been to turbocalculator but i dont get what they're saying :/ )

thanks a lot

[JaeTea]

www.howthingswork.com

They got illustrations and everything.

[vsp3c]

it's clear to me that you lack reading comprehension skills

[Jeff240sx]

Do yourself a favor and search Freshalloy for poster "Enthalpy" and keyword "turbo."
Honestly, Enthalpy, Scott, degreed engineer from Ga Tech, and probably smartest turbo/tuning guy I've ever talked to. He has tons and tons of great info there.
Then come back and ask any questions you have left. I know enough about the things...
-Jeff

[Jeff240sx]

it's clear to me that you lack reading comprehension skills

Ohhh! New guy owns noob! LOL!
-Jeff

[JaeTea]

it's clear to me that you lack reading comprehension skills

Nope just lazy. :mrmeph:

[vsp3c]

Ohhh! New guy owns noob! LOL!
-Jeff
look up vsp3c or jeong at nissanforums :p

Do yourself a favor and search Freshalloy for poster "Enthalpy" and keyword "turbo."
Honestly, Enthalpy, Scott, degreed engineer from Ga Tech, and probably smartest turbo/tuning guy I've ever talked to. He has tons and tons of great info there.
freshalloy is gay and won't let me search w/ usernames -__- plus he has 1000+ posts so blehhh

[MELLO*SOS]

Just go to your bookstore and buy this book:

http://a1055.g.akamai.net/f/1055/1401/5h/images.barnesandnoble.com/images/1590000/1595090.gif
Maximum Boost
by Corky Bell
(http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=O9t1bOwmOZ&isbn=0837601606&itm=1)

It will give you all the info you need to get you on your way to boostin your ride.Great investment if you're curious about turbos & turbo setups. Otherwise just go to google.com or howstuffworks.com.....

[wootwoot]

or go to amazon.com and buy the book for a lot cheaper

[Jeff240sx]

If you, yourself, don't know about turbos, don't post.
If you have a specific question about turbos, ask away.
-Jeff

[coldfire07]

I second the idea of buying Maximum Boost by Corky Bell. It is an amazing book.

[vsp3c]

bleh i dont wanna buy a book -__-

[MELLO*SOS]

If you're too lazy to go flip thru the book at barnes & noble, then you're never gonna have a decent understanding of turbos.

Otherwise go read this
http://auto.howstuffworks.com/turbo.htm

good luck...

[vsp3c]

If you're too lazy to go flip thru the book at barnes & noble, then you're never gonna have a decent understanding of turbos.
and i'm sure you know everything about turbos :rolleyes:

[91rusty240sx]

what are the pros and cons of AR??? what exactly is AR? do you change it on the compressor side? turbine side? both?

[mrmephistopheles]

vsp3c - stop being a selfish prick. You ask for help and people are trying to help you. Don't shit on them by complaining about what they're offering.

[Jeff240sx]

what are the pros and cons of AR??? what exactly is AR? do you change it on the compressor side? turbine side? both?

A/R is a ratio of the diameter of the inlet/outlet of the turbo divided by the distance between the center of the inlet/outlet and the center of the turbine.
Both housings have an A/R, but the turbine side is expecially susceptable to changes. Too large an A/R, the more flow, but the more lag. Too small and you'll choke off up top.
Compressor side is changable too. Too small and you'll not flow enough for alot of boost. Too large and major lag, but more efficiency. Everything about a turbo is a tradeoff.
There are generally accepted sizes for a KA and SR. A simple search will tell you the best of a certain size/type/compressor series turbo for your application. Simply asking what is best would be impossible to answer alone.
-Jeff

[mellojoe]

I'm going to go steal some info... be right back....


...ok...

Stolen from ARImport.com from Jeff aka "Swordfish" who is a turbo guru.

A/R
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.


CHRA - center housing rotating assembly
The CHRA includes a complete turbocharger minus the compressor and turbine housings.

Clipped Turbine Wheels
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.

Free-Float
A free floating turbocharger has no wastegate device. This turbocharger can’t control its own boost levels. For performance applications, the user must install an external wastegate.

GT
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.

On-Center Turbine Housings
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.

Trim
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:

Wastegated
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.


I can also help you read a compressor map if you like......
example map...
http://img.photobucket.com/albums/v451/lewroe/gt32compress.jpg

The numbers you see on the left, listed vertically from 1.00 to 3.60 is the pressure ratio. Let's say you are boosting at 7psi. This is roughly half of the sea level atmospheric pressure (14.7psi), so your pressure ratio is 1.5. if you're boosting 15psi(rounded up for simplicitys sake), your pressure ratio would be 2. The formula for figuring pressure ratio is: pressure ratio=(14.7+boost pressure)/14.7

The numbers you see on the bottom that start at 0 and end at 50 is the flow rate of the turbo measured in lbs/min(some are in cfm and some are in cms). This is the amount of airflow that you are wanting to push through your turbo.
Now that that is done look at the map again, the next thing to look at are the lines that make it look like a thumb print. Those line are effciency lines. The outer one being 65% effciency, and the inner one being 78% effcient(the effciency % differ from map to map, but should be marked on the lines). The area inside the 78% ring is the most effcient area or "island" of the turbos range. Getting your turbo to spend most of it's time in there will give you the most power at the lowest charge temperture.
Let's say you were boosting at a pressure ratio of 2.20 and were moving 30lbs/min worth of air. Follow those two lines together and you will find yourself almost right in the middle of the most effcient island. This is the ideal area to run your turbo. But let's say you want to boost at a pressure ratio of 2.6 and were moving the same 30 lbs/min worth of air, that would put you right between 78% and 76% effciency which is still good, but once you drop below 70% you might want to reconsider your turbo selection. You set your boost at 2.0 pressure ratio, but want to move 45lbs/min of air, this puts your point outside the turbos effciency range, this means that your turbo is to small, you could boost more to get the effciency up but notice how much more you would have to boost to increase the effciency.
This brings us to another bit of infomation; turbine speed. The horizontal lines that slope down towards the right of the map. That is the turbine speed measured in x1000rpm. Notice how at higher pressure ratio the faster the turbine spins and the lower the effciency and how suddenly the effciency drops compared to lower pressure ratios, going outside the top line on the turbine speed is were you decide to go with a bigger turbo(to much speed and you will just be making the turbo work harder and not as effcient). Now to the far left is the surge line, this is the point were the turbo starts to make boost at a given pressure ratio and turbine speed, you do not want a point on the left side of this line doing so will cause your turbo to surge at WOT, and when I mean surge I mean the turbo starts to spool but doesn't have enough turbine speed to build more boost and the car will start bucking madly and your boost gauge will start bouncing, this is murder on a turbo. It is imperative to size the turbo correctly so that this does not happen. In closing you have to figure out how much power you will be making at what boost levels and plot those points on the chosen compressor map to see where they fall in the effciency range of the turbo selected. I hope this is of some help, PM me with any questions that I haven't answered here or that you might have. Happy boosting.

[mellojoe]

Page 2

A/R = Area Ratio

Compressor Trim = (Inducer Diameter ^2 / Exducer Diameter ^2 ) X 100

Turbine Trim = (Exducer Diameter ^2 / Inducer Diameter ^2 ) X 100

And below is the one everyone leaves out but this one can be a killer if you get it wrong.

Expansion Ratio = (Exhaust Manifold Pressure + Atmosperic Pressure) / (Turbine Outlet Pressure + Atmospheric Pressure)

Also I noticed in the article that they listed the old school on center turbine housing but left off the housings that everyone actually uses. They are Tangential housings. Tangential doesnt mean that the housing is divided. It describes the exhaust gases angle of approach to the turbine wheel. There is Tangential is available in both divided and undivided designs.

[mellojoe]

Page 3

Their is a lot of weirdness in nomenclature of turbos. After the numbers come letters to designate T04 turbines.
O trim
P trim
Q trim
GTQ trim
R trim
GTR trim
S trim
GTS trim

Then the absolutely huge F Trim and G Trim. These are paired with 91mm compressors and larger.

Now for some compressor naming crap.
T04E and T04B nomenclature.
These are named in trims instead of compressor size like a straight T4. 46 trim, 50 trim, 54 trim 57 trim, 60 trim and then there is the 60-1, 62-1 and 66-1. These names are derived mathematically by the formula I listed in the above post with the exception of the -1 units. The -1's are based on compressor size like a full T4. 60-1 = 59mm compressor. 62-1 = 61mm compressor.

Full T4's compressors are named based on compressor size in millimeters. T66 = 66mm. T61 = 61mm and so on.

If it is a Greddy (mitsubishi) turbo then pay no attention to the numbers because they mean jack sh1t. A greddy T78 is not a 78mm compressor. Its a 66mm compressor. Their naming system is based on different features. I'll list those later.

Now, you also have to take into account the way different retailers name their turbos. Take forced performance for example. They have the red and the green. Doesnt tell you anything about the turbo. Then they have the FP3065 for example.
Looks like the FP stands for Forced Performance right. And maybe a GT30 turbine wheel and a 65mm compressor right? WRONG!

FP = Forced Performace so that part was righ
30 = GT 30 series turbine wheel. Its actually a GT35 but thats 30 series
65 = 65 lb/min compressor. Its a Garrett GT40 56 trim compressor which flows 65 lbs of air per minute.

Then their are the compressor cover names.
T04B = .50AR compressor housing
T04E = .60AR compressor housing
T04S = .70AR compressor housing
Then there are the T series which are just huge.

That should give you guys something to get your heads around for a while. I'll come back later to do the large greddy nomenclature and the small mitsu stuff as well.

Keep a few things in mind as well. Turbonetics is NOT Garrett. Precision Turbo is NOT Garrett. Innovative Turbo Systems is NOT Garrett. These are all Garrett based and some do use Garrett parts. But none of them are full Garrett turbos. These companies machine their own parts as well. Take Precision for example. Most of the compressor wheels, turbine wheels and even some full rotating assemblies are Garrett but the compressor housing and turbine house are manufactured by Precision. Therefore, they are not Garrett housings. Precision does manufacture some of its own wheels as well though. Like the 71mm billet compressors and such. Turbonetics doesnt use anything Garrett. They make all their own stuff. ITS is pretty much the same.
jeff

[mellojoe]

Page 4

Greddy Nomenclature

OK first we'll start with the small crap. 16G, 18G, blah blah. These turbos are basically named by what turbine wheel they have plus some arbitrary part number that mitsu has assigned to them. The bigger the "G" number, the more the compressor flows. Simple enough. Goes like this.

TD05H-16G. Turbine wheel is TD05H and 16G is compressor

Common turbine wheels are as follows.
TD04
TD05
TD05H
TD06
TD06S
TD06H
TD06N
TD07
TD08

Good enough.

Now for the big Greddy stuff whic is actually mitsu. Ready or not, here we go. We'll use the good ole T88 for this. Below are the different configs for the T88
T88-34D (22cm)
T88H-34D (22cm)
T88H-38GK (22cm)

The first letter, "T" denotes it is a Turbo charger. The second number denotes the exhuast turbine base spec (in this case, from an MHI-TD08) and the third letter denotes the compressor base spec (again, from an MHI TD-08).

The "H" denotes the use of a hi-flowed compressor housing.

In the second group of letters/numbers, the first number denotes the exhaust turbine wheel base spec, in the above cases all T88's use a type 3 exhaust wheel, as follows:

Type 3 spec: A/R = .77. Inner wheel dia. 79mm. Outer wheel dia. 90mm. Exhaust port throwoff dia. 94mm. Straight cut 12 spline wheel.

The second number in the second group denotes the compressor wheel base spec, either a Type 4 or a Type 8. The t78 uses a 33 or 34 spec exahust wheel.

The type 4 specs: A/R = .54. Inner wheel dia. 70mm. Outer wheel dia. 95mm. Inlet trumpet dia. 100mm. Straight cut 8 blade wheel.

The type 8 spec: A/R = .60. Inner wheel dia. 76mm. Outer wheel dia. 98mm. Inlet trumpet dia. 100mm. Slide cut aero 6/12 spine wheel.

The letters that follow the second group of numbers denote the compressor housing spec.

Type D spec: Conventional trumpet, from 100mm reduced into 70mm.

Type GK spec: Revised recirculation ports, using 100mm inlet.

Get it? Got it? Good....

jeff

[mellojoe]

Ok, and the reason I copied all this?

I had the exact same questions... Lots of good reading!

[kazuo]

FYI, FreshAlloy DOES let you search via username. Click where it says "AND" and you'll see you can choose "OR," or "BY DISPLAY NAME."

DISPLAY NAME = USER NAME

Some good info in this thread. Cut the e-thug-I'm-better-than-you bullshit and stick to turbo talk.

Thanks

[vsp3c]

finally some good info :D ty mellojoe

[mellojoe]

Here is some more information that I've been able to gather. I did some research and pulled some stuff from several sources. I even went straight to Garrett Turbos and got some information (the page 1 post has their definitions straight out of their brochure).


cfm (lbs/min) = (0.069) * (cid x rpm) / 3456

EDIT: cid = CUBIC INCHES of your engine.
Convert Liters to CC by multiplying by 1000 (approx).
Convert CC to CI by multiplying by 0.061.
(ie. 2.4L = 2400cc = 146.4ci)
(ie. 5.7L = 5700cc = 347ci)
(ie. 383ci = 6279cc = 6.3L)

This will give you the airflow that your car produces in stock form (N/A). You multiply this result by the pressure ratio to determine the amount of air your engine will flow WITH the turbo.

So, if you want to push 9psi of boost, you would have:
(9 + 14.7) / 14.7 = 1.61

cfm of stock x pressure ratio = cfm (lbs/min) with turbo

This is an ideal air flow, so factor in about 85% of that to be the real air flow.

cfm (lbs/min) with turbo x (0.85) = corrected cfm (lbs/min)

There we go!

So....
The best route it seems is to plot a few points (ie 3000rpm, 4000rpm, 5000rpm, 6000rpm). Then you plot those points on the chart. For my engine I am making a couple of assumptions... 1) Boost will hit by 3000 rpm, 2) Boost builds somewhat linearly until it hits boost at 3000rpm, 3) boost will remain mostly steady from 3000rpm through the powerband.

So, we plot those plot those points on a compressor map like this one (T3/T04E "50" Trim) shows for 9psi:
http://www.nissaninfiniticlub.net/photopost/data/500/10093t04e-50-9psi.JPG

This still doesn't all make TONS of sense, but it definately helps.

You can mix it up saying that you hit 9psi of boost at 3000rpm, 12psi at 4000rpm, 13psi at 5000rpm and 13psi at 6000rpm, or whatever. Sure you have to make a few assumptions, but this will help us get close.

These formulas can be plugged into a spreadsheet to make your calculations easier.

[Taffy]

Here are 2 websites that have some of the BEST info on turbos.

www.turbobuick.com This one is a bulletin board, so do a search on turbos.

www.gnttype.org Goto the tech section, then to turbos. There is more reading there than you can do in a week. All articles are written by guys that either are turbo nuts, have degrees in the field, or worked for Buick when the Turbo Regal was being built.

Happy reading.