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  1. #1
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    Default What turbos on a 350 build

    Hi guys
    I try to edjucate myself about turbos
    I read alot and at least i figured. The t3, t4, hybrid, GT difference pretty much.

    Im planing a350 Turbo build and
    Would like to know a efficent turbo with upside for a
    Twin build
    Single build

    Goals 650hp on low boost 7-9 psi

    Motor is a beefed up 350 wich ported heads and a ok cam LS112
    Like min. 360-380 hp i would say

    So

    What you suggest for each scenario..
    I dont mind "ebay" turbos

    BUDGET MINDED





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  2. #2
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    Default Re: What turbos on a 350 build

    The cam you have is NOT an OK cam for turbocharging!!!
    It is not just the LSA but the amount of overlap.
    Your present cam has at least 12 degrees too much overlap and that is mainly because of the long duration exhaust duration which is meant for Nitrous use.

    In order to get 650 hp on 9 lbs of boost the engine would need to have over 400 hp N/A with an 8.5:1 compression ratio.
    The cam would need to have more duration in order to move the torque peak to a higher rpm and the LSA would need to be 114* minimum.

    The problem with trying to make big HP with low boost is the engine needs to run at a higher rpm
    It would be better to use 15 lbs of boost at a lower rpm. There is a lot more torque available and the engine has much better street manners.
    Turbos also run more efficient at pressure ratios of 2 and above.

    Now here's the interesting part. It takes a larger turbo to make a certain HP at low boost than to make that same HP at a higher boost.
    It takes twin 55mm to make 650 hp @ 9 lbs of boost, It only takes twin 50mm @ 15 lbs.
    It takes a single 75mm @ 9 lbs but only a 70mm @ 15 lbs.
    Last edited by pmuller9; 01-10-2017 at 01:18 AM.

  3. #3
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    Default Re: What turbos on a 350 build

    Quote Originally Posted by pmuller9 View Post
    The cam you have is NOT an OK cam for turbocharging!!!
    It is not just the LSA but the amount of overlap.
    Your present cam has at least 12 degrees too much overlap and that is mainly because of the long duration exhaust duration which is meant for Nitrous use.

    In order to get 650 hp on 9 lbs of boost the engine would need to have over 400 hp N/A with an 8.5:1 compression ratio.
    The cam would need to have more duration in order to move the torque peak to a higher rpm and the LSA would need to be 114* minimum.

    The problem with trying to make big HP with low boost is the engine needs to run at a higher rpm
    It would be better to use 15 lbs of boost at a lower rpm. There is a lot more torque available and the engine has much better street manners.
    Turbos also run more efficient at pressure ratios of 2 and above.

    Now here's the interesting part. It takes a larger turbo to make a certain HP at low boost than to make that same HP at a higher boost.
    It takes twin 55mm to make 650 hp @ 9 lbs of boost, It only takes twin 50mm @ 15 lbs.
    It takes a single 75mm @ 9 lbs but only a 70mm @ 15 lbs.
    I see...i ll adress the cam later.. As said before i have to try out the cam
    .
    Regarding ebay turbos
    55mm turbos are GT30 s?
    50 mm turbos are t3/t4 hybrids?

    Gt35s are to big?

    If single i was looking at t76 or t78

    What you think

    Quote Originally Posted by pmuller9 View Post
    The cam you have is NOT an OK cam for turbocharging!!!
    It is not just the LSA but the amount of overlap.
    Your present cam has at least 12 degrees too much overlap and that is mainly because of the long duration exhaust duration which is meant for Nitrous use.

    In order to get 650 hp on 9 lbs of boost the engine would need to have over 400 hp N/A with an 8.5:1 compression ratio.
    The cam would need to have more duration in order to move the torque peak to a higher rpm and the LSA would need to be 114* minimum.

    The problem with trying to make big HP with low boost is the engine needs to run at a higher rpm
    It would be better to use 15 lbs of boost at a lower rpm. There is a lot more torque available and the engine has much better street manners.
    Turbos also run more efficient at pressure ratios of 2 and above.

    Now here's the interesting part. It takes a larger turbo to make a certain HP at low boost than to make that same HP at a higher boost.
    It takes twin 55mm to make 650 hp @ 9 lbs of boost, It only takes twin 50mm @ 15 lbs.
    It takes a single 75mm @ 9 lbs but only a 70mm @ 15 lbs.

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  4. #4
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    Default Re: What turbos on a 350 build

    Quote Originally Posted by Sebambam View Post
    Im planing a350 Turbo build and
    Would like to know a efficent turbo with upside for a
    Twin build
    Single build

    What you suggest for each scenario..
    I dont mind "ebay" turbos
    The biggest factor on a single or twin turbo set-up is engine compartment space and packaging.
    If you do a single, where would it mount and how to get the exhaust to it from both engine banks.

    Twins on a Buick 350 usually end up just above and out from the heads between the first 2 cylinders but you can get creative and find 2 spaces elsewhere.

    Your engine presently has Hooker headers on it. What would you for an exhaust system to the turbochargers?

    Quote Originally Posted by Sebambam View Post
    Regarding ebay turbos
    55mm turbos are GT30 s?
    50 mm turbos are t3/t4 hybrids?

    Gt35s are to big?

    If single i was looking at t76 or t78

    What you think
    GT30s and T3/T4 hybrids come in a range of sizes so they are not necessary 55mm or 50mm.
    You would need to look at the compressor inducer size of the turbo in question.
    Better yet is if there is a compressor map for the turbo for you to look at.

    Most GT35s would be too big.

    A T76 might work for a low boost application but it is too big for boost 12 lbs and above.
    You would need something around 70mm.

  5. #5
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    Default Re: What turbos on a 350 build

    Quote Originally Posted by pmuller9 View Post
    The biggest factor on a single or twin turbo set-up is engine compartment space and packaging.
    If you do a single, where would it mount and how to get the exhaust to it from both engine banks.

    Twins on a Buick 350 usually end up just above and out from the heads between the first 2 cylinders but you can get creative and find 2 spaces elsewhere.

    Your engine presently has Hooker headers on it. What would you do for exhaust plumbing to the turbochargers?



    GT30s and T3/T4 hybrids come in a range of sizes so they are not necessary 55mm or 50mm.
    You would need to look at the compressor inducer size of the turbo in question.
    Better yet is if there is a compressor map for the turbo for you to look at.

    Most GT35s would be too big.

    A T76 might work for a low boost application but it is too big for boost 15 lbs and above.
    I try to learn more
    Is there a goid lecture?

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  6. #6
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    Default Re: What turbos on a 350 build

    The first 21 pages of the Garrett catalog is very informative.
    Pages 7-12 are the most important.

    https://dl.dropboxusercontent.com/u/...Catalog_V5.pdf
    Last edited by pmuller9; 01-10-2017 at 06:25 PM.

  7. #7
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    Default Re: What turbos on a 350 build

    Quote Originally Posted by pmuller9 View Post
    The first 21 pages of the Garrett catalog is very informative.
    Pages 7-12 are the most important.

    https://dl.dropboxusercontent.com/u/...Catalog_V5.pdf
    Thanks alot..


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  8. #8
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    Default Re: What turbos on a 350 build

    Quote Originally Posted by Sebambam View Post
    Thanks alot..
    If you have any questions or need clarification on the material please ask.

  9. #9
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    Default Re: What turbos on a 350 build

    Quote Originally Posted by pmuller9 View Post
    If you have any questions or need clarification on the material please ask.
    Im on it... Tryiing to learn..thanks for the support..

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  10. #10
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    Default Re: What turbos on a 350 build

    Update?

 

 

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