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Thread: Help planning turbo build in a Sierra

  1. #41
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    Re: Help planning turbo build in a Sierra

    Quote Originally Posted by sigurko View Post
    Please educate me. Could you, or anyone else on this thread, post a picture of a "good" and "bad" piston, where the relevant difference is visible, and point that difference out, with a big red arrow -)

    Thanks in advance.
    all std type pinto pistons have big slots, if you take the oil rings off you can see them, forged is the only way to get off the shelf ones without slots, or try to find a piston from some other type of engine which is ok

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    Re: Help planning turbo build in a Sierra

    Of course it is a simplification but remember the first post; Not a full on race car. keep the budget sane

    :-)

    I kind of think you need to start somewhere and by far the easiest way to give an indication of what might "work" for a build like this is boost pressure. Combine that with what Onyd said about how the engine is to be used (don't build a cheap Pinto turbo to tow a heavy trailer in the Alps!) and I that is sufficient for what the poster wants to know.

    Keep it reasonably simple, so that you actually get something done and have fun :-)

    Gustaf

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    Re: Help planning turbo build in a Sierra

    First post in this thread shows the two types of oil return path behind the oil control ring. Cant link the images directly here

    holes = ok
    slots = will break

    http://club4ag.com/forums/viewtopic.php?f=13&t=11414
    9.85 @ 145mph 202mph standing mile

    https://www.youtube.com/watch?v=Ss_c7fML3rw

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    Re: Help planning turbo build in a Sierra




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  8. #45
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    Re: Help planning turbo build in a Sierra

    Thank you for the clarification. It is now clear to me, why is this the weak spot of the OEM pistons.

  9. #46
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    Re: Help planning turbo build in a Sierra

    Quote Originally Posted by kliobas View Post
    I basically agree with everything written here except that I do not understand how you define the reliability only by using boost pressure. Different turbos create different airflow at the same pressure, therefore different torque which kills the piston.
    My small experience suggests that 260Nm/4400RPM and approx. 200 BHP was fine (boost pressure was 0,7), full boost at ~4100-4200 RPM as far as I remember.

    That's correct, 0,7 bar will give approx 260 Nm (can be lower as 4400 RPM) and 200 Bhp and is just within "save". The lower the boost comes in (small turbo) the faster it will be at the edge. Big turbo's can't push that hard in lower revs and are for one time safer. This does not mean it can't go wrong. It will be boost that kills the piston. Boost means cylinder filing in a correct build turbo engine and more cylinder filling will be harder for the piston.

    BTW, the original clutch usual let go round 240 Nm.

  10. #47
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    Re: Help planning turbo build in a Sierra

    It did but it's fairly easy to solve the issue with transit flywheel, cosworth clutch and mt75 gearbox, almost bolt on

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