Need help with turbo sizing

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Need help with turbo sizing

Postby sins23 on Fri Jun 13, 2008 6:54 pm

What turbo would be big enough for a 3.x L engine ?

Would like something with an internal WASTEGATE, turbo elbow, and SS exhaust wheel.(will however consider ceramic wheel)
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Re: Need help with turbo sizing

Postby Nave on Fri Jun 13, 2008 9:35 pm

They aren't really sized for the engine so much as they are sized for power. The size of the engine plays a part of course, but what matters most is what you want out of it. Say you have a 3L engine, you could put a "big" turbo on it and make the same power a "small" turbo would make. The difference might be the "big" turbo is barely working to make that power, it's below where it operates efficiently and doesn't spool until 6000rpm while the "small" turbo is above where it operates efficiently and you are pushing the limits of it's reliability. Both are extremes, yes, but you should still be thinking about it when sizing your turbo. If you know you want big power, get a big turbo. If you know you want relatively low power but a responsive kick, get a small one. If you have no idea what you want go for a ride in an example of each. Once you decide that you can choose the right turbo for your application, engine size is all part of the application.
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Re: Need help with turbo sizing

Postby sins23 on Fri Jun 13, 2008 10:26 pm

Ok, that i understand, and my fault for not specifying :)


I have a 3.4L engine,

i'm looking for a turbo that will give me 10PSI within it's efficiency range. decent spool time,

I currently have a T-70 but it's too big for what i want out of a turbo'ed engine.

i'd be looking at an RB25 turbo, or toyota CT-26 ideally.
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Re: Need help with turbo sizing

Postby Nave on Sat Jun 14, 2008 12:35 am

You still haven't said a power goal and what you are doing with the car.
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Re: Need help with turbo sizing

Postby sins23 on Sat Jun 14, 2008 2:34 am

stockHP on the 3.4 block is 205HP.

i'm looking for about 285~325 crankHP
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Re: Need help with turbo sizing

Postby DJPyro on Sat Jun 14, 2008 3:10 pm

Get some sort of T2, GT2871R, or GT28RS should do the trick, it'll nail your power goals and then some, and it'll give you ridiculously quick spool.
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Re: Need help with turbo sizing

Postby Nave on Sat Jun 14, 2008 3:40 pm

Which engine?
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Re: Need help with turbo sizing

Postby sins23 on Sat Jun 14, 2008 3:58 pm

this is going on a GM3400SFI
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Re: Need help with turbo sizing

Postby Drift_240 on Sat Jun 14, 2008 5:26 pm

You should probably look into this issue with people more experienced with your specific engine. If you are serious you probably have a lot of research to do.

5 seconds on google i came across this
http://www.grandamgt.com/forum/showthread.php?t=48117

also have you considered a supercharger setup with an eaton m62 maybe, They had them on the 3800 SSEI Bonnevilles and stuff for years
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Re: Need help with turbo sizing

Postby sins23 on Sat Jun 14, 2008 5:37 pm

The supercharger setup would require more work than a turbo setup.

reason being is the 3400 is a 660 and the 3800 is a 690 block.(6 cylinders@90degree opening)

The turbo setup, i've already done on a 3.1 using a t25, while very quick to spool, was choking at the end of the powerband. @ 8PSI.


ideally looking for a used GT28RS(dicso potato), in good condition WITH elbows.
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Re: Need help with turbo sizing

Postby thetest on Wed Jun 18, 2008 10:41 pm

if there are big ones and small setups, why isn't there a medium setup?
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