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Turbo experts: need some input.

Zack

4 Doors 4 Life
Mar 21, 2004
6,297
20
NW Indiana
Im starting to gather parts for my upcoming turbo project.

Problem is, I have no idea how to properly select the correct A/R.
Im definitely using a 76mm precision (or comp) billet wheel turbo.
Both sides will be 2.5" piping merged together, and a 4" downpipe.
Then it will split into the stock dual exhaust.

Since its a 4500lb car, I was thinking the .82 A/R is what I should go with, but then I heard I may have backpressure issues at the top end.
Since im totally clueless, any advice is appreciated.
 

1MEANGT

Braaaaaaap!!!
Mar 18, 2004
8,815
2,121
A lot depends on how much power you want to make? Also how fast you want the turbo to spool. Plus there are way more factors, compressor maps, ect. But that is getting deep into it.

I run a .96 AR on my Precision 78mm. Spools fast and makes awesome power. Pulls hard all the way through the top end and I see full boost at about 3500 RPM. Though I have more cubes which makes a difference.

What are you looking to do with this setup?
 

Zack

4 Doors 4 Life
Mar 21, 2004
6,297
20
NW Indiana
I drive the car everywhere, and the engine is already built with 9.5:1 compression.
Also, the fuel system is setup for big power already.

So, I just need to make 12-13psi on 93 then turn it up when I put E85 in it.

Nothing fancy, just want a turbo...bad.

Oh, Im not after a power number, I already know it will make a lot. LOL
 

1MEANGT

Braaaaaaap!!!
Mar 18, 2004
8,815
2,121
The .82 A/R will more then likely work out perfect for what you want to do. If it becomes a restriction then just swap it out to a .96 housing.

Precision told me the smallest turbo I should go with is a 88mm. Which is probably true on my combo but my 78 works perfect and is awesome on the street. Does not take long to spool at all and easily got me to where I want to be for now.
 

Spoolin D Dub

"THE BOSS" But you can call me sarge!
Sep 21, 2012
201
0
Just Around da Corner
Im starting to gather parts for my upcoming turbo project.

Problem is, I have no idea how to properly select the correct A/R.
Im definitely using a 76mm precision (or comp) billet wheel turbo.
Both sides will be 2.5" piping merged together, and a 4" downpipe.
Then it will split into the stock dual exhaust.

Since its a 4500lb car, I was thinking the .82 A/R is what I should go with, but then I heard I may have backpressure issues at the top end.
Since im totally clueless, any advice is appreciated.

what size motor do you have?
 

Pressure Ratio

....
TCG Premium
Nov 11, 2005
20,303
11,728
Glen Ellyn
The .82 A/R will more then likely work out perfect for what you want to do. If it becomes a restriction then just swap it out to a .96 housing.

Precision told me the smallest turbo I should go with is a 88mm. Which is probably true on my combo but my 78 works perfect and is awesome on the street. Does not take long to spool at all and easily got me to where I want to be for now.

Did you order a 88mm for a winter upgrade yet? Lol
 

1MEANGT

Braaaaaaap!!!
Mar 18, 2004
8,815
2,121
Mike needs a 91 or 94 mm turbo. He has a way better motor than I do.





Op, twins are easier to package usually. And usually better suited for a street car. Better boost response and such. But call a pro for recommendations for sure. There is A LIT that goes into picking a correct turbo for a combo.

Would need to re-do the hotside of my kit to put an 88 on it. And how do I have a way better motor then you..........lol

I love my 78 on the street. Sees boost almost instantly when I nail it and I have plenty of power with room to grow. Besides, it is a street car. :smile:
 
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