Question on forged internals

Supranos

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Hey all, this is my first post ever on here but I've spent quite some time this afternoon trying to a get a solid answer on the b58 internals. I am aware the rods and crank are forged but are the positions forged as well or just cast? I can't seem to get a solid answer anywhere and would like to know for my personal knowledge.





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Supranos

Supranos

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Maybe check the papadakis engine tear down of the b58?

I saw that whole break down but unless I'm missing something, he didn't say anything about the pistons did he? Again sorry If I missed it
 

KahnBB6

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My guess is that the rods are cast and the pistons are "semi-forged" hypereutectic which allow for far greater strength than simple cast pistons but much better expansion and contraction control properties (for better oil blowby control, cold startup noise control and long term cylinder wall wear) than true forged aluminum pistons.

It's apples to oranges but the stock pistons in all the non-VVT-i 2JZ-GE's and all 1JZ-GTE and 2JZ-GTE engines were all "semi-forged" hypereutectic type for these same reasons. Although not all semi-forged piston designs are going to be equally as strong for every engine design.

A few supercar manufacturers still use true forged OEM pistons but it's kind of rare. Cast piston quality and strength may have improved quite a lot from where the technology was in the 1990's but I'd still bet on the B58C & D using hypereutectic pistons given the high boost performance application. Cast pistons are good for many applications but not so much when it comes to high boost pressure in relatively small displacement gasoline engines used in high performance models.

Someone please correct me if I'm wrong though.
 

DatBassTho

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My guess is that the rods are cast and the pistons are "semi-forged" hypereutectic which allow for far greater strength than simple cast pistons but much better expansion and contraction control properties (for better oil blowby control, cold startup noise control and long term cylinder wall wear) than true forged aluminum pistons.

It's apples to oranges but the stock pistons in all the non-VVT-i 2JZ-GE's and all 1JZ-GTE and 2JZ-GTE engines were all "semi-forged" hypereutectic type for these same reasons. Although not all semi-forged piston designs are going to be equally as strong for every engine design.

A few supercar manufacturers still use true forged OEM pistons but it's kind of rare. Cast piston quality and strength may have improved quite a lot from where the technology was in the 1990's but I'd still bet on the B58C & D using hypereutectic pistons given the high boost performance application. Cast pistons are good for many applications but not so much when it comes to high boost pressure in relatively small displacement gasoline engines used in high performance models.

Someone please correct me if I'm wrong though.

Dropping a knowledge bomb and then asking to get corrected 🤣 I love learning on these forums!
 

KahnBB6

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Dropping a knowledge bomb and then asking to get corrected 🤣 I love learning on these forums!
It’s just what I have learned over time but I always defer to info and opinions from the pros and engineers. To the best of my knowledge everything I said above is accurate though.

When I was trying to decide on what pistons to use in my 2JZ I researched every piston type available from OEM to all forged aftermarket types because the OEM NA and TT pistons aren’t available in overbore sizes.

But... for my application I wasn’t sure if I could get away with using widely available 2618 forged pistons and 4302 4032 forged examples were nearly mia unavailable.

(Fun fact- for Toyota JZ engines only Arias still *sometimes* makes batches of 4032 forged aluminum 2JZ pistons. Every other company only offers 2618 forged aluminum. Although I did not get around to checking with Mahle and Cosworth though during my research.).

Cast aftermarket pistons were totally out. Those aren’t even up to the quality and strength of the OEM pistons.

In the end I finally went with the stock bore brand new OEM hypereutectic pistons because my machine shop determined my block needed no overbore and was still well within spec in each cylinder.

Here’s a good short video that talks about the main differences between each type of piston:

 
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