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What turbo size???

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Old 03-01-2016, 02:37 PM
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Default What turbo size???

Ok so I'm looking into going single turbo kit on my goat. It's an ls1, throwing in some compstar h beams, and diamond pistons. Anyway, just curious on what turbo sizes you guys recommend for a 347. I'm looking to make a max of 650whp. Would like to either go borg or precision but any advice is welcome. I'm just trying to make sure I do my build properly.
Old 03-01-2016, 02:53 PM
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pt7675
Old 03-01-2016, 03:01 PM
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Seems to big for the power I want to run?? Is it laggy??
Old 03-02-2016, 07:30 AM
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I agree with him, that's a good Precision for a stock cube LS1 wanting to make 650+. From there larger or smaller is simply preference.

As for Borg, the small wheel S475 is like $650 and probably makes a bit more power (not to mention more reliable), but they're physically huge and hard to fit in a GTO.
Old 03-02-2016, 06:14 PM
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I see. Are the Turbonetics 7668 to small?? I know i want at least a 76mm compressor side but what about turbine side is 68 to small??
Old 03-02-2016, 06:51 PM
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7675 all day. it will also give you room to grow a little. I know you only want 650 right now. but that 7675 will do over 700 if you ever want a little more power. I know I started out just wanting 400 rwhp ten years ago, now I'm heading towards 800rw and wanting more haha
Old 03-02-2016, 07:45 PM
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Why do you want 'at least' a 76mm compressor? My 74mm is making huge power, and I haven't even pushed it to the point where I need more than cheap pump gas.

I'd stay away from the 7668 on a 5.7. Turbine side is just a little small.
Old 03-02-2016, 08:50 PM
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Idk. Just trying to find a turbo that isn't going to be laggy. Don't wanna spend 1500$ either. That 7675 just seems big for the power i want? Might consider just buying an lm7 and drop that in too.
Old 03-02-2016, 09:19 PM
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Lag can be helped by other things besides turbo sizing. But you said you wanted at least a 76mm and then said the 7675 sounded too big. They are one in the same.

The 7675 is a little expensive for mild power levels like that and a 7668 can make the power you want just not much more. For a little more money you can get a 7875 from Turbonetics and it will make plenty of power and support more later.

For less money you can get the Chinese copy of the 7875 from on3 and still meet you goal for like half the price.
Old 03-02-2016, 09:25 PM
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S475/77 1.10 A/R & go from there.

You going to add a cam to it? It will make hitting the mark a tad easier.

Oh &
Old 03-03-2016, 01:41 AM
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P-Trim 66mm T4 Turbo will get your goal just maybe

PT 6266 CEA get you your 650+ rwhp not much left yet would be ready for boost always..

PT 6766 CEA turbo, a bit overkill for 650 rwhp yet would be responsive and have room to grow..about 800 rwhp capable


You will probably find with a capable bottom end your going to be wanting more of that feeling Boost gives!! enjoy whatever you do....tune wisely and patience with timing advancing....its a killer!

Last edited by Rudy72; 03-03-2016 at 01:42 AM. Reason: spelling
Old 03-03-2016, 06:16 AM
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Those CEA turbos are expensive!

Personally, I would probably go 7875 from On3, or 7577 from Borg Warner. Both cheap, both capable of more than 650whp.
Old 03-08-2016, 08:23 AM
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Originally Posted by 1bdbrd
Lag can be helped by other things besides turbo sizing. But you said you wanted at least a 76mm and then said the 7675 sounded too big. They are one in the same.

The 7675 is a little expensive for mild power levels like that and a 7668 can make the power you want just not much more. For a little more money you can get a 7875 from Turbonetics and it will make plenty of power and support more later.



For less money you can get the Chinese copy of the 7875 from on3 and still meet you goal for like half the price.


I guess what I'm saying is the 7675 is good for 1000hp. Im shooting for 650whp. When i read the numbers that's why i was like it seems a bit big for my power. I mean i guess i could add a quickspool valve. I don't know? I guess i just really don't understand what you need as far as turbine side and such for it to be a sufficient turbo for a v8. Thank you for information though i appreciate it!
Old 03-08-2016, 08:26 AM
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Thanks everyone for chiming in. I guess i shall look at all of these different turbo options.
Old 03-08-2016, 01:51 PM
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Problem is you're just taking the compressor into consideration. Too small of a turbine will be a restriction on the exhaust. I would recommend looking at a minimum 80mm to 87mm turbine wheel single that will be very responsive but not restrictive. We had excellent results with a Master Power 76mm GT45 1.05 A/R ex 6-bolt exhaust outlet flange. Compressor and turbine wheel diminsions are very close to the Precision PT7675. I've seen Chinese copies on Ebay and a genuine Master Power made in Brazil can be bought for around $700 new. 69mm Borg Warner S300SX-E will support 900+ on the compressor but will choke the exhaust before that even with a 1.00 exhaust housing. Keep in mind the S400 Borg Warner compressor housings are huge in comparison to any of the Garrett copied compressor housings.
Old 03-09-2016, 08:18 AM
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Originally Posted by 00Wildcat
Problem is you're just taking the compressor into consideration. Too small of a turbine will be a restriction on the exhaust. I would recommend looking at a minimum 80mm to 87mm turbine wheel single that will be very responsive but not restrictive. We had excellent results with a Master Power 76mm GT45 1.05 A/R ex 6-bolt exhaust outlet flange. Compressor and turbine wheel diminsions are very close to the Precision PT7675. I've seen Chinese copies on Ebay and a genuine Master Power made in Brazil can be bought for around $700 new. 69mm Borg Warner S300SX-E will support 900+ on the compressor but will choke the exhaust before that even with a 1.00 exhaust housing. Keep in mind the S400 Borg Warner compressor housings are huge in comparison to any of the Garrett copied compressor housings.
I see. Ya as far as compressor side i knew i needed 74mm minimum. As far as turbine side i wasn't sure. So at least an 80mm? I don't know how well that s400 fits on the goat? Those are big aren't they??
Old 03-09-2016, 08:40 AM
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That turbonetics 7875 spools pretty good. 1300 dollars though. Just drives me nuts how expensive it is. I guess you get what you pay for though...
Old 03-09-2016, 07:16 PM
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On3 makes a "clone" of that turbo for a huge amount less. I say it like that because a few on here talked about the on3 possibly using the same parts as the turbonetics turbo it's just assembled here like the name brand one is.
Old 03-10-2016, 01:59 PM
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I run the 7875 from Turbonetics on a stock block ls1. You'll have no issues hitting your power goals, and will hit full boost before 3500rpm.
Old 03-11-2016, 04:31 PM
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Originally Posted by 1bdbrd
On3 makes a "clone" of that turbo for a huge amount less. I say it like that because a few on here talked about the on3 possibly using the same parts as the turbonetics turbo it's just assembled here like the name brand one is.
The On3 78/75 is $399 right now I believe.


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