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Turbo guys :: What A/R are your turbos and why?

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Old Jul 11, 2009 | 01:42 PM
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Default Turbo guys :: What A/R are your turbos and why?

I've been doing a bit of research in the world of FI and I've gotten to the point where I understand the schematics and technology alot more that I did before. My question is what A/R are your turbos and what influenced the you to use that selection? I'm planing a stock cubed TT build and I've concluded that a Stage V T3/T4 Hybrid with .63 A/R would do the trick. My understanding is the the Stage 5 Turbine, which is 62mm, will allow me to make adequate power with a stock LS1 as well as all me to turn up the boost once I forge my bottom end. The 0.63 A/R will spool early, but the only thing I'm concerned about is if they will consistently produce boost up to 7k. So please, share you experiences with me.
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Old Jul 13, 2009 | 01:47 AM
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I run a .96 a/r hotside with a 6.0 litre and I shift around 6k. I chose it because a .68 would have fallin off a little early and I still have full boost by around 3500/3600
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Old Jul 13, 2009 | 11:55 AM
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the best thing to do would be to find out how much air those turbos can push each then find out how much air your engine will need at 7k. Forcedinductions.com has a chart that goes up to 6800 rpm and 15psi.

but with a twin turbo using to small turbos that will spool fast anyway you might want to think about a higher ar. call sponsers and ask them.
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Old Jul 13, 2009 | 12:05 PM
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thanks guys.

close thread
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Old Jul 14, 2009 | 01:14 PM
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My twin .68 AR stage V 60-1 Garretts get full boost as early as 3500 and hold to 7200. The ability to spool sooner or later can be controlled with an EBC as well.
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Old Jul 14, 2009 | 02:36 PM
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Originally Posted by TXZ0603
The ability to spool sooner or later can be controlled with an EBC as well.
I assume that stands for electronic boost controller
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Old Jul 14, 2009 | 02:46 PM
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Correct. You can change the way it spools to a degree. By changing the gate pressure ( what psi it starts to open the wastegate ) you can move the spool time. For my application, my low boost is on spring pressure ( 7# ) the factory GP set was 3#. By holding the gate closed longer ( say 4# ) I can make it reach full boost sooner. Change it to say 2# and it will reach later.

Other things to consider is what is the AF while going into boost? By maker it slightly richer ( from what Ive been told ) it will achieve boost faster. Just some more things to look at.
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Old Jul 15, 2009 | 12:49 PM
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Originally Posted by TXZ0603
Correct. You can change the way it spools to a degree. By changing the gate pressure ( what psi it starts to open the wastegate ) you can move the spool time. For my application, my low boost is on spring pressure ( 7# ) the factory GP set was 3#. By holding the gate closed longer ( say 4# ) I can make it reach full boost sooner. Change it to say 2# and it will reach later.

Other things to consider is what is the AF while going into boost? By maker it slightly richer ( from what Ive been told ) it will achieve boost faster. Just some more things to look at.
So an ebc can do more than just hold boost @ x psi....

hmmm... thanks for the useful info, I might be picking up the twins this weekend; Turbonetics T3/T4 Stage 5 (62mm c.w.) .81 A/R; hopefully i can start my build thread by Halloween....
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Old Jul 15, 2009 | 03:04 PM
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I run a 76mm T4 with a .96AR on the hot side, stock motor.

I went with that because thats what my friend had and he made me a good deal, turns out its a pretty good choice for my motor.
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Old Jul 15, 2009 | 03:42 PM
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Originally Posted by WS6HUMMER
I run a 76mm T4 with a .96AR on the hot side, stock motor.

I went with that because thats what my friend had and he made me a good deal, turns out its a pretty good choice for my motor.
on stock compression as well?? when does boost build and peak?
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Old Jul 15, 2009 | 04:02 PM
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Originally Posted by IT_SS
on stock compression as well?? when does boost build and peak?
Yes stock compression, it starts building boost at about 1800 and hits max boost at about 4400.
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Old Jul 15, 2009 | 04:16 PM
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Originally Posted by WS6HUMMER
Yes stock compression, it starts building boost at about 1800 and hits max boost at about 4400.
does it maintain maximum boost?

lol, like you can notice a drop in boost @ wot from 4k thru 7k
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Old Jul 15, 2009 | 04:33 PM
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i have a .70 with my 5.3 and a ls2 cam ... that should work out good for me eh?
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Old Jul 15, 2009 | 04:35 PM
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Originally Posted by IT_SS
does it maintain maximum boost?

lol, like you can notice a drop in boost @ wot from 4k thru 7k

Not right now, its been bleeding off 1.5 to 2 psi. I did find that the v band flange was leaking on the wastegate and a torn o-ring in the gate. Just got all that straight this morning before work and hope to give it a try soon.
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Old Jul 15, 2009 | 06:07 PM
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Not trying to hijack the thread but will my turbo be to small? Its a forged 347 with a precision t76 .75 compressor and .96 ar hot side. I plan on running 16-18 psi will it not do that? Will it max to early?
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Old Jul 15, 2009 | 06:51 PM
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^^^^

you should be fine
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Old Jul 16, 2009 | 11:06 PM
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good info guys, thanks!
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Old Jul 18, 2009 | 02:09 AM
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Originally Posted by 02anti_vnm
Not trying to hijack the thread but will my turbo be to small? Its a forged 347 with a precision t76 .75 compressor and .96 ar hot side. I plan on running 16-18 psi will it not do that? Will it max to early?

can anyone explain those numbers in bold? i think the .96 determines how large the tubo flows or am i dead wrong? i don't know crap about what a compressor does on a turbo?
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Old Jul 18, 2009 | 02:37 AM
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Originally Posted by airforcemanss
can anyone explain those numbers in bold? i think the .96 determines how large the tubo flows or am i dead wrong? i don't know crap about what a compressor does on a turbo?

Check out the stickies and also www.forcedinductions.com for some good info. Basically the turbine AR determines how quick you spool up vs. how much top end power you are going to make. It's a delicate balancing act so you still spool well, but don't choke yourself out on top.
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Old Jul 18, 2009 | 06:37 PM
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i c. i have looked at thread several times i guess ill go peak at again i might of missed something thanks.

what about the compressor?
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