Clearing up some Turbo Info

[FordGuy100]

All these posts about turbo's are almost getting on my nerves. Turbo's arent that crazy hard to understand. Sizing can be generalized (although specific and precise sizing should be used before buying a turbo for any application).

So...let me try to introduce a little knowledge. If I'm missing anything, just add to this post.

First off....A/R Ratio tells you NOTHING about the size of the turbo except for the....get this....A/R ratio. Ratio meaning two numbers, one over the other number, so using math, you divide them. Thats the A/R ratio. Now, how does one measure the A/R, to find both the A, and the R value's? Well this is it. The A is the inducer side of the wheel, that is, basically the size of the inlet of the turbo (where your intake connects). The R value is way more complicated. You take the centerline of the wheel (the center of the bolt that holds the wheel in place) and measure to the outlet of the housing. Thats for the compressor (cold) side. The opposite is true for the exhaust side, as the exhaust doesnt come in in the middle of the turbo, thats the outlet. Reference: http://www.supracentral.com/articleimages/arhousing.jpg

So, A/R has nothing to do with size other than the ratio of those two numbers. For example:

Lets say you have a compressor housing you want to figure out the size of. Wow, it has a large inlet of 5" (our turbo's have what, 3" inlets?), we then measure from the center of the wheel to the center of the outlet and we get 7.13" inches. I mean this compressor housing is massive. We take that 5" and put it over 7.13" for the model of: 5/7.13. Doing the math, that turbo has an A/R ratio of .70.

Wait a second...that large of a turbo only has an A/R of .70??? What??? I mean looking at my compressor housing it also says, and I quote "A/R .70." But mine is much smaller than the turbo in the example. Well, thats cause A/R is just a ratio.

Or for another example, we find this little tiny compressor housing, its got an inlet of 1", and a R value of 1.43", this is a really small turbo. But, the math shows, once again, it only has an A/R of .70.

Now all you need to know to find out how big the turbo compressor or turbine housing really is, is either an A or R value. Basically have someone just measure the inlet to the compressor side, or tell you what size the turbine inlet is (T3, T4, they are fixed numbers, you can calculate that). Once you get that value, have them tell you the A/R that goes along with it, some simple math ensues, and there you go, you can see how big of a turbo it is.

Also, I was talking about the compressor side A/R...which really isnt that big of a deal. A/R is more used for the exhaust side. You figure out the mounting of the turbo, T3, or T4 or whatever, and the A/R. A T3 (smaller A) with an A/R or 1.00 is a smaller housing than a T4 with an A/R of 1.00. The T3 is smaller as the the equation is as follows: A/R= A/R therefore 1.00 (T3, therefore smaller than the T4)A/R has to equal one, but since the T3 has a smaller inlet, the R has to be smaller to equal that same A/R of 1.00, so its smaller.

 

[MUDKICKR]

i dont understand, i think im going to start a new post

 

[82F100SWB]

For compressor sizing, have a look here, lots of reading:
http://www.oilburners.net/forums/showthread.php?t=18059&page=2&highlight=twin+turbos

I suggest Corky Bell's maximum boost for some very good reading.

 

[1994IDI]

Good write up Justin. Should clear up some turbo sizing confusion.

 

[typ4]

Thanks tons for this Justin, I wasnt going to go into detail because my typing sucks.

Very well explained

 

[BrandonMag]

Very good info!

i dont understand, i think im going to start a new post

 

[ghunt]

A/R ratio doesn't tell you anything about a turbo, but looking at turbine A/R numbers can often give you an idea of how quickly the turbo will spool or whether it will be a flow restriction at higher RPM's.

Compressor A/R gives you sort of an idea of how much air the compressor can move, but otherwise it's not all that useful.

Compressor wheel trim is the most useful thing to know, but I don't even think I could explain that well enough to help much...I feel like I'm still trying to understand it myself

 

[FordGuy100]

I was just using compressor side as an example, as my compressor has it's A/R number cast into it. I would agree A/R of the turbine housing is much more important.

What it boils down to is this, don't ask someone what A/R their turbo us without asking either the compressor inlet size, or turbine mounting (T3, T4 ect) as without that info A/R means nothing.

 

[redneckaggie]

Well since we are on the subject of turbos

I dont know the exhaust flange type for this rajay turbo but here are the measurements according to this pic that i found

exh a=2.46875 b=.375 c=2.875

intake a=2.125 b=.25 c=3.03125 50 trim

compressor a/r=.23


exhaust a/r=.59

center bolt to center bolt on flange 4 1/4in x 2 3/4in

if you need any more info i would be happy to provide it but just trying to ask someone that knows a little more than me

does anyone know how to get a map for this thing? or maybe can tell me theoretically how it would work.

 

[rwilles]

Hey Justin,

I'd guess I'm one of the posters that's 'driving you crazy'! Thanks for the summation. I've been asking with the incorrect assumption that most turbo systems on these trucks are the OE system (would be interesting to find out the percentages!) Mine also has the .70 A/R on the compressor housing. A question for clarification: Is the inducer size or the inlet size used for the calculation? I've seen both ways in my searching.

The OE turbo is the Garrett TC-43 which is based on the T 04b-h trim with the waste-gated elbow. The inducer is 2.3" and the inlet is 2.5".
Using the inlet size to calculate area= 3.1415*(0.5*2.5)squared= 4.9085square inches.
With an inverse calc the radius inside the housing would be 4.9085"/.7=7.0122sq". Correct so far? The 'upgraded housing' claims a 13% increase in flow would require a like increase in area 7.0122sq"*1.13=7.85"sq. the hard part is that those changes can be in either the width or height of the housing.

I'm still trying to figure how to identify from some external dimension what the ATS 'housing upgrade' is and have been asking for the measurements on the upgraded system and thought that the A/R ratio would be a quick shorthand to find the upgraded new part! As the housing doesn't seem to have a manufacturer marked on it, is there a better question to ask?

Does someone have an 'upgraded housing' that some measurements could be taken from?
From the ATS web site (http://www.atsdiesel.com/ats2/productdetail/2029043158):
(This is really confusing because the words say compressor (cold) housing while the pictures show the housing bolted to the elbow and down-pipe (hot) side. I'm concluding that the copywriter knew not what he was writing about! But this very well could be one of those moments i only think i have a clue!)

"The ATS Ported Shroud Compressor Housing, designed to increase your turbo life by eliminating the damaging effect of compressor surge. When performance products are added to increase horsepower, the compressor wheel accelerates faster and compressor surge and flutter becomes more apparent and damaging.

Our Compressor Housing is designed with a 4" intake and exclusive inducer bleed ring. This results in a 13% increase in choke flow allowing more air into the compressor wheel, and inducer bleed broadens the range of the compressor wheel, smooths out air flow and eliminates turbo compressor surge."

Without real measurements it is almost impossible to find the housing with any of the manufactures. Borg/Warner in my best bet right now.

 

[ghunt]

Sounds to me like ATS has something screwed up, because that description is talking about one of their Powerstroke upgrade compressor housings from the sound of it.

There's nothing different about the turbine housing on their upgrade kits- all the change is in the exhaust elbow, which is enlarged to 3". I assume that's what they're talking about if they're touting increased flow.