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Turbo Tech 101 and 102

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#1
Bill@SiR

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Ok.  

 

I added some info on a topic on the other board, and it seems a lot of turbo info is a black art.  

 

Well here is how I explain it!

 

Turbos are basically Exhaust driven compressors.  They have a turbine wheel driven by the exhaust and a compressor wheel driven by the turbine wheel. (Left is the compressor wheel, on the right is the turbine wheel)

 

IMG_0230_0.jpg

 

A GT-R has 2 basic types of Turbos.  Stock Frame Turbos and Aftermarket Manifold turbos

 

A Stock frame turbo takes a Stock GT-R Turbo

2012-08-14 01.14.40.jpg  

You can see the 1pc Exhaust manifold and turbine housing. 

 

Here you can see the turbine side, on the left is the wastegate hole, on the right is the turbine wheel.  This is a Stage 1 turbo (I will get into the sizes a little later on)

2012-08-14 01.16.08.jpg

 

The exhaust goes through either the turbine wheel and increases the turbine speed (And corresponding compressor speed), or out the wastegate hole to regulate boost (Closed makes more boost, as it forces more exhaust through the turbine wheel, Open does the opposite)

 

The other basic style of turbo in the GT-R is the upgraded manifold.  

 

Here is an example of an AMS A10/A12 kit.  You can see the header off the engine is 1pc, and the turbo turbine housing is a separate piece, and the wastegate is again a separate piece.  

 

ams_alpha_10-12_kit_4.jpg

 

This allows for significantly more flow from the exhaust manifold, turbo and wastegate.  Increasing efficiency from pumping losses (Less back pressure) and allowing for larger turbo sizes.

 

 

 

 

 


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#2
Bill@SiR

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Turbo Sizing (it is off the top of my head so if you find a mistake let me know)

 

Turbos have 4 basic measurements.  Compressor and Turbine, Inducers and exducers

 

Garrett_rotating_group_enlarged.jpg

 

That gives a general ideal of the size and flow potential of a said size.   Generally larger makes more power and spools slower. 

 

Things like Blade area, blade pitch, number of blades, blade height effect flow and response.  But that's a little more advanced subject. 

 

In general the Inducer measurement of a compressor wheel, effects how it does at low boost, and the exducer size effects higher boost pressure ratios. 

 

Lets look at the OEM GT-R turbo Specs

Compressor (6+6 blade design)

Inducer 43.3mm

Exducer 56.1mm

 

Turbine (9 blade design)

Inducer 52.4mm

Exducer 39.9mm

 

Lets look at some popular GT-R Turbo upgrades for the stock manifold

 

Lets use a GTX3071 as en example (Not exactly my stage 3 but similar, my compressor wheels do have a larger exducer + extended tip)

Compressor wheel (11 blade design)
Inducer 54.1mm
Exducer 71.4mm

Turbine Wheel (10 blade design)
Inducer 60mm
Exducer 54.8mm

EFR6758
Compressor wheel (7+7 Blade Design)
Inducer 53.9mm
Exducer 67mm

Turbine Wheel (10 blade design)
Inducer 58mm
Exducer 51mm

 

 

HTA2871

Compressor Wheel (7 Blade design)

Inducer 51.2mm

Exducer 71mm

 

Turbine wheel (9 blade design)

Inducer 53.9mm

Exducer 47.1mm

 

 

SiR Stage 1 

Compressor Wheel (6+6 Blade Design)

Inducer 46.5mm

Exducer 60mm

 

Turbine wheel (12 blade design)

Inducer 53mm

Exducer 48mm

 
SiR 1.5

Compressor Wheel (11 Blade Design)

Inducer 50.9mm

Exducer 70.5mm

 

Turbine wheel (12 blade design)

Inducer 53mm

Exducer 48mm

 

 

Lets look at some popular Aftermarket Manifold turbos

 

GTX3076R

Compressor Wheel (11 Blade Design)

Inducer 58mm

Exducer 76.6mm

 

Turbine Wheel (10 blade design)
Inducer 60mm
Exducer 54.8mm

 

 

HTA3076

Compressor Wheel (7 Blade Design)

Inducer 54.8mm

Exducer 76mm

 

 

Turbine Wheel (10 blade design)
Inducer 60mm
Exducer 54.8mm

 

GTX3582R

Compressor Wheel (11 Blade Design)

Inducer 62.5mm

Exducer 82.5mm

 

 

Turbine Wheel (10 blade design)
Inducer 68mm
Exducer 62mm

 

 

HTA3586

Compressor Wheel (7 Blade Design)

Inducer 62mm

Exducer 86mm

 

 

Turbine Wheel (10 blade design)
Inducer 68mm
Exducer 62mm

 

 

 

Next up is airflow potential.  A GTX3071R has a rated flow of 55lb/min from garrett, a EFR6758 has a rated flow 49lb/min from borg warner  Keep in mind thats the rated flow of the COMPRESSOR wheel.  

Things do change a bit when you stuff them down into OEM GT-R Housings.  I can say the flow is potential is lower.  I actually changed my wheel dimensions after some testing, so the turbos like Scuba Steve have and Doug3223 have are my custom GT-R housing dimensions.  (Basically as big as you can go to try and boost efficiency in the OEM compressor housing)

 

The other thing to think about is how bit the OEM housing is.  With anything bigger than about 56-57mm you must be VERY careful on the turbine side. 

2013-05-25 02.23.51.jpg

Here you can actually see the air in the casting.  it gets very thin when you go this far.  And steps need to be taken to ensure longevity in a turbo of that size.  


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#3
Bill@SiR

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Turbo Technology 102...

 

Going to highlight a few topics that are most relevant to GT-R guys. 

 

Back-pressure. 

 

Back-pressure is a measure of restriction in a turbo system and efficiency.   Exhaust has a maximum air speed.  That speed is very close to the speed of sound (its actually slightly above it)  What happens is as boost and airflow goes up, the exhaust speed goes up.  The smaller the turbo system, the higher the speed will be with the same volume of air.  Next what happens is that air naturally wants to go a certain speed (the speed that it exited the engine).  Now its being forced into a much smaller opening, the air speed goes up, and a restriction begins.  Now that high air speed is great for turbo feel and spool.  But it is not good for back pressure related restriction.  Once the exhaust cant go any faster, pressure builds to force it out (and it also forces it BACK IN a motor through reversion, and contaminates the incoming charge of air)

 

In general the Backpressure measurement is generally expressed as a pressure ratio between manifold pressure (AKA boost pressure in the engine) and Turbo pressure in the turbine housing.  In a Stock Turbo GT-R, this is actually fairly high, at relatively low boost pressures.  At 15psi of boost in a stock turbo GT-R (at lets say 7000rpms) the back pressure is above 35psi. It is in the 2.4-2.5 to 1 range.      In general the higher the rpm (or airflow of the motor) the higher the back pressure will be.  

 

So if you want to optimize an RPM range, turbo housing sizes play a big role, and effect back pressure directly.  If you want a drag racing motor, going to a GT35 with a 1.06 AR might make more sense (Ratio of inlet and turbine size, the higher the AR Ratio, the more flow the housing has in a given size)

 

With a stock manifold GT-R you are stuck with the size of the inlet and turbo nozzle.  So when you go bigger the ratio changes actually smaller.  Since the manifold did not change and the turbine got bigger.  A typical AR Ratio for a stock frame turbo is around .40 AR (or very small), This is great for spool, but not great for pressure build up and subsequent heat build up. 

 

NOT all AR ratios are the same.  Since its a ratio, if both numbers change, you can maintain a Ratio, but have a different size and flow.  Lets take for example a VBand housing for a HTA3794 (67 Inducer Compressor, 65mm Exducer turbine)  And compare that to a PTE 6766 T4 housing.  

Lets say both have the Same AR Ratio, but since the PTE T4 housing is larger in both measurements, it has much higher flow and much lower back pressure, and will make a good amount more power.  (And require cutting the frame to fit them LOL)

 

The other BIG topic with back pressure is Camshafts.  If you change how an engine pumps air, how long the valves are open, how long they are overlapped, etc you can effect back pressure directly.  Also RPM range and boost effect back pressure a lot too.  

 

A lot of guys think I am a miracle worker when I retune a car with lower boost, lower timing, richer AFR, and make more power and or go faster at the track.  It is mostly the understanding of back pressure that is the key here, and its effects on how an engine does work.  

 

I am looking for the Goldilocks number, of maximum boost with minimum back pressure. 

 

Ok well thats back pressure.  

 

When guys refer to "Billet wheels" in a turbo they are referring to the compressor wheels.  Its "Technically" a Machined Forged Billet compressor wheel.

 

By going billet, it allows to change the blade design, blade pitch, number of blades, wheel height, hub thickness, Curve and wheel dimensions.  These are all great things and allows a small batch change (its cost effective to make as little as 10 forged billet wheels at a time)  

 

For example, On my billet wheels, I do custom dimensions and wheel height, and custom hub thickness. You can notice in this photo, the bottom is thinner, the wheel is taller and thinner, the extended tips are wider.  

 

This is something a guy like me can do.  The wheel on the left is made by garrett a HUGE company, and because of modern technology a little guy like me can make something that can compete with them.  (all be it on a MUCH smaller scale)

 

 

That same type of technology, small production, optimized for a certain size, engine, or even camshaft can be applied to the turbine wheel as well.  As far as I know I am the 1st GT-R "Tuner" to put a "Billet" Forged Inconel material turbine in a GT-R.

Turbine.jpg

 

This allows me to optimize blade height, blade dimensions, hub dimensions, Number of blades ect.  So I can make the perfect turbine for the application.  This is an even lower volume type of operation because of the machine time involved.   

 

Any turbine wheel from a large manufacture is going to be cast.  The costs involved in doing a machined turbine are relatively high, and the break even point on doing a casting is as little as 25pc.  So this is a very low production method of manufacturing, but it does allow for designs that cannot be cast.  


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#4
Todzilla

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Nice contribution Bill. 


2011 Nissan GTR Gun Metallic
Switzer P800
Switzer Premium 90MM Stainless Steel Exhaust
Switzer Engine Cooling Package
Cobb AccessPort

H&R Springs
Custom Pine Tree Air Freshener from AutoZone

ADV 10 Deep Concave Wheels with Pirelli P Zero Nero Tires 355/25-21 / 285/30-21 Titek Lugnuts

 

IMG_0148-1.jpg


#5
Tim

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Thanks Bill,I just learned something today :) and that's a good day
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#6
doctorspeed1

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Thanks Bill. Your a great asset to the community on the forum and locally.

#7
PianoProdigy

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Great stuff.  I certainly respect that you may not want to share, but I figure I'll ask anyways, what are the specs on the USM?



#8
icarus

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Very nice, appreciate this info!


2014 NISSAN GT-R
Racing Brake - HKS - GotBoost Performance - AMS

#9
Bill@SiR

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Just updated post number 3 with turbos 102 ;)

 

 

Great stuff.  I certainly respect that you may not want to share, but I figure I'll ask anyways, what are the specs on the USM?

 

To be perfectly honest I am not going to share.  I spent a lot of time, effort, money, and R&D into the custom wheel sizes.  Its not hard for a competitor to buy my turbos and measure the wheels.  But I would rather make them buy it.

 

The only other thing I have going for me, is a lot more than dimensions goes into turbo performance.  When I buy my billet wheels, I use very high quality parts.  This costs me a LOT.  I could source the same looking, same dimension part for less than 1/4 what I am paying from my supplier.  I believe that honoring my existing business relationship, as well as working with someone that shares the same passion as me for performance, and technical expertise is key.  

 

I can make a 51/70mm compressor make more power than a 54/71 compressor in a GTR with the same turbine.  Those numbers are general guidelines for performance.  

 

I know that no one else is going to spend $400ea on billet wheels (thats my cost, look around online and you can buy that general size for as little as $65ea, fully custom)

 

Against my better judgement I am going to post 1 reason why. 

 

I make my wheels thinner than anyone else you can see that below.  

 

compwhel.jpg

 

Now I did the R&D, I did the Computer analysis, I did the material analysis.  And figured out how thick the blades could be made in that given size.   Could you copy that? Sure.   But they would not know what i know, and the steps I took to make it work. 

 

So I know that gives me a performance advantage, and I know the machining processes I use make more power, with better response as well. 

 

Could someone make a USM sized turbo for 1/2 the cost, probably.  But it wont perform the same.

 

 


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#10
audioenvy

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Good info!



#11
ian.r

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awesome writeup! Bill you have proven yourself on this platform fo sho, and seeing all the results it speaks volumes

glad we have your expertise available to provide parts and services, it clearly shows in your builds.

i remembered what i said in chat about proving what you can do, and ive seen alot. i owe you beers!

(sad that sometimes people dont see any of this and get all bitchy sometimes).
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#12
Tim

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(sad that sometimes people dont see any of this and get all bitchy sometimes).[/quote]

Just let the haters keep drinking big buckets of Haterade,we also appreciate you putting up with all of are questions in chat
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#13
Fabshopmiami

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Very cool.



#14
icarus

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Obviously you have a lot of careful analysis and R&D in your stock frame turbos.  Do other companies providing GT-R stock frame turbo upgrades also spec out and customize their turbine and compressor wheels and other components of the turbo?  Or are the GTX, EFR, HTA offerings just a mass-produced turbo not specific to GT-R?


2014 NISSAN GT-R
Racing Brake - HKS - GotBoost Performance - AMS

#15
PianoProdigy

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I just read every word again trying to digest everything more fully.

 

I like that Ben posted lots of pics of the EFR stock frame setup here: https://www.facebook...73460388&type=3

 

It is neat to examine everything closely now that I know a bit better what I'm looking at, lol.



#16
Jiaim

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Does the USM uses the forged turbines ? nice



#17
Bill@SiR

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Does the USM uses the forged turbines ? nice

No they do not

 

For example.  Some company's forged compressor wheels cost as little at $50 complete.  They can produce it with 10 to 20 minutes of machine time.  And aluminum is pretty cheap at $1lb, Even with that, my compressor wheels take 2.5 to 3hr to complete, and off the shelf wheels are $350-500ea.  

 

My forged milled turbine wheel, takes 8-10 hours of machine time, and a $30 per lb (you also need a pc about 4x bigger than the compressor wheel, due to the fact you have a 1pc design, and that includes the shaft) The cost is $2000-2500ea for the turbine wheel. Its expensive.  Thats the main reason you don't see them widespread.

 

When a Casting fee is $20,000 and the turbo wheels are $2000ea, it pays to do a casting at a fairly low production number.  


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#18
Bill@SiR

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Obviously you have a lot of careful analysis and R&D in your stock frame turbos.  Do other companies providing GT-R stock frame turbo upgrades also spec out and customize their turbine and compressor wheels and other components of the turbo?  Or are the GTX, EFR, HTA offerings just a mass-produced turbo not specific to GT-R?

 

Just saw this. 

 

GTX, EFR and HTA are off the shelf units, that are not specific to GTR.  The choice is what size to put in.  Not Changing the size profile. 

 

A few guys made custom dimensions, and I make custom dimensioned compressor wheels in like the 1.5 and USM.  And I have made the turbos for a big build I am doing with the Forged Turbines.  That way I can put a high flow turbine in a smaller housing.  The customers goals are going for max power with non frame cutting turbo dimension.  



#19
Doug3226

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It's pretty cool that Bill is sharing all this information, it took me a long time to understand more boost does not automatically mean more power. Bill has done a great job of explaining this to me and even proving it to me with my own car on the dyno.

 

Tim it would be great if this thread could be pinned...so much good information here, This should be a must read for anyone looking to upgrade turbo's


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#20
Tim

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Ask and you shall receive .Bill thanks again for sharing all this info :)
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