Turbo speak-definitions and data

Hot COCOAL

May the farce be with you
Jun 9, 2012
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So, since I can't find anything specific like this, I figured it would be bennificial to start a thread where newbs like me could learn the technical data revolving around turbos.

Also, in this thread, I thought we could start adding and compiling info about different turbos, so there could be sorta a do all and be all informational area about turbos for our duramax powered trucks:thumb:

Please try and keep input to technical info, I am hoping that this will be a helpful thread, and it's easier to keep interest pure, and curiosity peaked and knowledge flowing, when there is not a shitstorm to read through:hug:

The below info was found by me from various sources. Including, and not limited to: turbo by Garrett/ Honeywell, Nelson Racing, turbonetics, car craft magizine, and various forums

Here we go:D

Some things I have recently learned:

Turbine: the set of blades/bladed wheel, that is driven by the exhaust, the housing for the turbine is typically (if not always?) made out of cast-iron, this wheel is responsible for harnessing the exhaust gases and their representative energy, and transferring that energy to the compressor via the common shaft shared by both wheels

Compressor: the set of blades/bladed wheel driven by the turbine, connected by a common shaft that rides on bearings/bushings. There are many variations of these wheels and are commonly upgraded for various purposes. This is the side of the turbo housing or wheel responsible for pulling in and compressing fresh air and creating boost pressure to the cylinders

Trim: this term refers to the dimensional change in diameter that is found on the turbine and compressor wheels. The wheels are narrower at the "top" and wider at the "base", the calculation of the amount of change in diameter between the top and base of the wheel is the trim number( I can't find if this is a percentage or what? Sorry) generally speaking, the larger the trim number, the more air, or gas volume the wheel can move, which leads us to....

Inducer and Exducer: The terms inducer and exducer refer to the parts of the wheels that face the inlets and outlets of their respective housing. On the compressor wheel, the the small diameter of the wheel is the inducer, as that is where the air is drawn into the housing and the larger diameter of the wheel is the exducer as that is where the drawn in air exits the wheel, on the turbine wheel the larger diameter of the wheel is the inducer as this is where the exhaust gases enter to drive the wheel(s) and the smaller side is the exducer as that is where the gases exit. Forgive me here, cuz I haven't found the definable correlation to spool up and inducer/exducer ratio or size, only that basic knowledge, that the bigger the wheel the longer it takes.

Bearing(s): the what the common shaft that goes between the compressor and turbine housing rides on. The bearings are lubricated/cooled by pressurized engine oil, brass bearings or bushings are found in less expensive applications and are very durable, while more expensive applications will typically utilize a ball bearing cartridge, when changing from a journal bearing to ball bearing cartridge an oil pressure reducer/regulated needs to be implemented due to the fact that the ball bearing unit requires less oil for lubrication and will spin with greater ease or more freely which leads to faster boost response or quicker spool.

A/R
Doesn't meant "air ratio"
Actually the term A/R should be written/stated A/R Ratio and means ASPECT RATIO RADIUS. It is defined as this- Area Radius Ratio (A/R) refers to how much the volume of the housing decreases from the air inlet to the compressor OR turbine wheel, measured at the point in direct center line with the wheel shaft closest to the inlet(on turbine) and outlet(on compressor)

It is a calculation of how much smaller the volute becomes to the center of the housing, the A/R has the most profound effect to the turbine side of the turbo, a smaller A/R will spool faster and produce power/boost quicker, where as a larger A/R will spool slower but create more top end power. Of course, it's not that simple though...

Variable vane technology turbo: include AVANT (automatic vane adjustable nozzle technology) VGT (variable geometry turbo) VGNT (variable geometry nozzle technology) They all mean the same thing as far as I can tell, just had to be different/named different for patent rights. Basically, there are "vanes" , "fingers" or "nozzles" (take your pick) that sit around the turbine wheel of the turbo charger, these vanes move into or twist toward the turbine wheel depending on algorithm's of demand as seen by the ECM. When the demand and rpm is low the vanes are closer to the turbine wheel, allowing for an effectively smaller A/R, which allows the charger to be very responsive, as the demand and rpm increase, the vanes move out or twist away from the turbine wheel, allowing for more gases to move more freely and allow for more top end power, effectively splitting the two worlds or really taking the split out of the old turbo sense of " big turbo big lag big power, small turbo small lag small power" with vgt technology you can effectively have your cake and eat it to, so to speak, as well as enjoy more fuel efficiency.

That about does it for now, sorry for the book, but I am sure there is more info available, I had to get it off my chest and out of my mind. I hope this helps anyone who was needing some clarification, and I hope I represented everything accurately, I didn't write anything down, just sorta compiled it all in my head, feel free to correct anything that needs to be, as the whole purpose for this is knowledge.

Also, I hope that this thread will be used to compare chargers, like tech data between any and all chargers whether it be two borgs of the same frame size or different size, or a Garrett and a Borg, or an HTT or HX, whatever, just be sure to list all valuable info, such as

Manufacturer, designation, turbine and compressor size, trim, A/R Ratio, cfm it moves, flange style(t3,4 or 6) and maybe power goal, if its been on and proven tell us how much power it has made.

Cool:cool:

I hope this turns out to be an awesome and informative thread:thumb:

Thanks for the support:hug:

:hello:
 
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Hot COCOAL

May the farce be with you
Jun 9, 2012
4,433
0
0
:eek:

:stop:

Trader...


















:cool2: just kidding, that's cool, just wanted to enrich this forum, it's my favorite forum and I try not to link to others, but good info is good info, even if the source is not desirable....it still helps, besides, most the posts there were made by guys that are members here anyways, and it is a damn good thread
Thanks



:angel:
 
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nwpadmax

comlpete diphsit
Aug 17, 2006
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Why don't you just go buy the books by MacInnes, Bell, or Miller?

All this stuff is explained in those in much better detail. And sometimes there is value in reading several authors because each one explains in it their own way and it can shed some light on a concept you may be struggling with.
 

LWATSON

future trans limpers
Jul 30, 2008
2,587
1
36
55
Scotland Neck NC
Why don't you just go buy the books by MacInnes, Bell, or Miller?

All this stuff is explained in those in much better detail. And sometimes there is value in reading several authors because each one explains in it their own way and it can shed some light on a concept you may be struggling with.
He's just trying to bring something useful to the forum and I for one appreciate it. I dont completely understand turbo tech and the terms used and the way things work. This writeup has shed light on a few things for me and I'm sure I'll revert back to it from time to time for info. Thanks CoCo!!!
 

adeso

wait, what?
May 30, 2011
1,569
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Minot, ND
I had a huge write up somewhere I will try to find it. and there is a thread on compD with about every turbo size out there and the rated CFM
 

Magnus

New member
Jun 22, 2013
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A/R

Area/radius is actually a ratio involving the airflow path vs turbine size at distinct points along the path of airflow through the volutes. Bacisally if you take the cross sectional area of the volute at a point along the path of flow, and compare that to the radius from turbine wheel center to the centerpoint of your cross section... You get A/R. A large A/R housing means the volute exhaust flows through is large in relation to the turbine wheel the exhaust is directed onto. It's not necessarily a universal measuring stick, as housing designs can have varying A/R if you measure different points along the volute depending on housing designs and that's not even considering different manufactures have different wheel designs and some (eg Holset) prefer to give housing sizes in "critical area" measurements instead.

A/R only really relates an apple to an apple, eg a T4 S366 .9 A/R will spool faster and flow less exhaust volumetrically than a T4 S366 1.32 A/R assuming the same wheel designs.

Compressors also have varying A/Rs, but most automotive turbos are tight housings with few if any options available.
 

Magnus

New member
Jun 22, 2013
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You can sort of see how the BD diverter valve would work... In a divided entry turbine housing, a diverter forces exhaust gases into one of the two volutes (probably the one further from the exducer). By forcing the gases into the narrower volute, flow velocity is accelerated at the cost of increased drive pressure. The faster flow impacts the turbine blades with more kinetic energy effectively allowing the turbo to spool as if it had a tighter A/R housing. It's a low tech white trash VGT with only two settings.

That's a pretty simplistic explanation, but there's no point to getting into boundary layer behaviors at different Reynolds numbers or trying to solve for the perfect turbo system with differential equations or Riemann sum approximations.

Use charts, do mass and volumetric flow calculations, pick turbos that fit for ALL OPERATING CONDITIONS not just WOT screaming down the track because nobody likes reading about how someone's "ideally sized for HP goals" S4-- doesn't work for towing detuned at 65% throttle.
 

jkholder09

New member
Jan 8, 2012
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Maryland
all turbo catalogs have an introduction page on reading the compressor and turbine maps as well.
I think borg and turbonetics even have an app/program you can download to help you size them up.