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Thread: Stayer. Pistons.

  1. #1
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    Default Stayer. Pistons.

    Hi friends!
    Continue your project. I wrote earlier that for the construction of necessary engineering approach. That is, first done structural calculations. After that begins the process of compiling details. In this topic I want to talk about the pistons.
    To obtain a power of about 300 HP (N/A) for the 4G69, I need to get a CR 11.8 : 1. This cannot be done with stock pistons. Therefore, I need custom pistons.
    I considered various options. For example, well-known companies (Wiseco, CP, Cosworth, etc.) do the pistons. The problem is that all these pistons are forged. Don't think forged pistons are cool. Doubt?
    In this case, ask yourself the question, why not install forged pistons from the factory? Why the best and the most powerful cars from the factory, have the cast pistons?
    Yes, forged pistons are more durable. But they have a significant disadvantage. This thermal expansion.
    Cast pistons have the clearance 0.02-0.04 mm.
    Forged pistons have the clearance 0.06-0.10 mm.
    A lot or a little? Because of this, forged pistons have a higher noise level. And most importantly, they do not go more than 30k miles. Further, the oil flow rate becomes simply monstrous. Drops the compression in the cylinders. There is a sharp engine wear.
    While cast pistons will run 200k miles (or more)
    Also, if you make cast pistons for modern technologies, the strength can be increased significantly. In this topic, I want to tell you how to make pistons.

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    First comes the design stage. I did the calculation, I need to CR 11.8
    Is measurement of the volume of the combustion chamber, the volume of the cylinder-head gasket recess in the piston, etc.
    Further work in the computer.





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    Next, we obtain a drawing of what we need to.

    I have done porting the cylinder head. I have big valves on the inlet and outlet. Therefore, the undercut valves are oversized.
    When all drawings are ready, we can start production. I mean, in Russia, it is possible to make a detail of any complexity. Originally done casting in a metal mold.

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    The pistons are cast under pressure. Aluminum alloy is very durable.
    It has a large silicon content. This is called a hypereutectic alloy. I'm not sure that in English it sounds right.



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    Next you need to obtain high strength alloy. The pistons are hardened at a temperature of 520 C for 8 hours.
    Further, the stage of aging. 14 hours at a temperature of 190* C.

    The alloy is gaining a very high strength and hardness. The stock pistons do not have such strength.
    Why is it done?
    The factory, the stock pistons have very low resistance to detonation.
    The stock piston will break the barriers between the rings. This is not my photo, I brought them for example.





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    After the pistons acquired a high strength, you can start machining.

    This is done on precision machines.
    Further, it is necessary to apply coatings. On the lateral surface of the piston to apply a Teflon coating black. This really reduces the resistance of the piston friction.





    On the upper surface of the piston is applied with a ceramic coating zirconium oxide. In these pictures the top coating is not done yet.
    Last edited by stayer; 24-08-2017 at 06:27 PM.

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    In the upper part of the piston is made of ceramic coating. It keeps the temperature of the gases inside the cylinder and does not spread to the engine parts. On average, this gives an increase of 5-8% capacity. Now the pistons are ready to install.











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    The cost of one piston $ 150 USD.
    Can make any configuration, under any degree of compression, etc.
    Thank you for your attention.

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