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01-09-2024, 01:35 PM | #1 |
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Forged Pistons for the S65B40(V8) engine
Hi Bimmers,
Can someone help me find a set of forged pistons, preferably coated (92.00 mm at 12.0CR) I need them to rebuild my engine. which will have a VF620 kit fitted. Suggestions and contacts are much appreciated. |
01-09-2024, 02:01 PM | #2 |
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S85 builder knows everything about these engines. All of your questions should go to him.
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01-09-2024, 05:58 PM | #3 |
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Stock S65 pistons are forged and coated
https://www.mahle.com/en/products-an...iston-systems/ |
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DrFerry6748.00 |
01-10-2024, 05:05 AM | #4 |
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mahle powerpak
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01-10-2024, 08:34 AM | #5 | |
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UPSROD1015.00 herrubermensch47.00 |
01-10-2024, 08:57 AM | #6 | |
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That’s Weak! I think I’m going to have to get Mahle aftermarket pistons for my refresh. |
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01-10-2024, 08:33 PM | #7 |
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It's cost efficient for them and has better NVH properties as a street car, which is why most OEMs don't go with forged on their street cars. If you're going to be boosting the engine you really want to go with forged. CP / Carrillo have solutions too. Mahle aftermarket is a good solution that should really be plug and play, but you really should balance the new assembly as tight as you can. Not really sure how much money you want to throw in to this tho.
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charliev68243.50 a5m794.50 |
01-10-2024, 09:20 PM | #8 |
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https://www.ecstuning.com/b-mahle-mo...197843622~mhs/
I think I’m going to go with this as soon as it becomes available. Seems like a direct plug and play |
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01-11-2024, 04:34 PM | #10 |
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01-11-2024, 08:15 PM | #11 | |
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01-11-2024, 08:24 PM | #12 |
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forced induction engines are more susceptible to detonation, the top edges of cast pistons often times are where they will get damaged, catastrophically. That's why it may be better to lower the CR if you are going to make it forced induction. It's really up to how you have it tuned, many guys reduce the built in safeguards in pursuit of more power.
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01-11-2024, 11:51 PM | #13 |
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I feel it’s just insurance to run forged pistons. All this time I thought we had forged pistons from the get go!
Most of us run tunes and our compression ratio is 12:1. I think forged pistons are prudent in case of an abnormal ignition event. Also, the motor revs to 8600! If you are running FI it’s stupid, not to run forged pistons. Anyways, $1500 for a complete set of Mahle forged and coated Slugs is not bad. |
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01-12-2024, 11:23 AM | #14 | |
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Recent Past '12 E92 M3 ZCP, '08 E93 M3, '18 F80 ZCP, '04 E46 M3 I think I have an M3 problem. |
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01-19-2024, 10:08 PM | #15 |
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Just wanted to share some new insight…
After talking to some of my colleagues within the Porsche community, I’ve come to realize that cast piston choice by BMW was purposeful and not them being cheap. I had the pistons professionally cleaned and a very reputable engine builder stated to me that our pistons are very robust and expensively cast. Meaning, it was not them cutting cost. BMW chose to use cast pistons to ensure engine longevity and to combat bore scoring. Porsche went from cast pistons to forged pistons and the results were more bore scoring problems with their later engines. It has to do, mainly with the expansion rate of the pistons and the looser tolerance requirements of the forged piston. The result was, more rocking in the bore causing more wear and tear over time. |
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01-21-2024, 01:41 AM | #16 |
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Good video explaining the difference, and why forged isn't always better:
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01-23-2024, 05:22 PM | #18 |
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With their budgets it’s apples to oranges. If you are ever in the paddock for a top fuel drag event you’ll see them tearing the engine down after every pull. It’s nothing for them to blow holes in pistons and heads running on nitromethane.
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01-24-2024, 10:41 AM | #19 |
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Those top fuel mechanics must hold the time record for engine rebuilding. I haven't been to a top fuel meet in ages but I remember the sound and the thumping I felt on my chest.
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03-03-2024, 04:53 PM | #20 |
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Okay. I’m contemplating between https://www.ebay.com/itm/19566871873...mis&media=COPY or https://www.ecstuning.com/b-mahle-mo...197843622~mhs/
To Forged or Cast, that is the question! The price difference is not a big deal (~$600). I love the idea of having “stronger” internals with a bump in compression but should I mess with BMW’s recipe? There are definite benefits to running cast pistons in a street motor! |
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05-25-2024, 11:40 AM | #21 |
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I weighed these pistons and found out that the Pins are 20 grams heavier than oem. The actual piston alone weighs the same as cast oem. Would 20 grams of additional weight in the Pin require a Crankshaft rebalance?
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06-10-2024, 02:02 AM | #22 |
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These are beautifully forged 4032 Pistons on the OEM Rods. The wrist pin is a heavier duty pin that brings the weight up 18 grams. With the ARP Rod Bolts bringing down the weight 8 grams, I’m overall 10 grams heavier. Talked to my friend who builds Air-Cooled Porsche engines professionally…said it should be perfectly fine and should not upset the balance at all.
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