how do hyper pistons work?

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modok
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Re: how do hyper pistons work?

Post by modok »

i know guys.
That's why I said NOT running engine.
You can turn an engine off, and re0-start it. If you shut it off hot and wait 30 seconds, there is no more temp gradient.
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Re: how do hyper pistons work?

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Truckedup wrote: Thu Jun 14, 2018 11:49 am What engine? I race vintage British Triumphs and do build some street engines, iron cylinders, around 3 inch bore...Normal cast piston, not low expansion, .0045 minimum. Modern forged pistons, .0055 minimum...Anything less will result in a seizure if the engine detonates..
yeah that's exactly what I'm thinking, .002 is too tight, even if it IS some kind of lower expansion piston.


If you really want to know,, It's a Vw cylinder, adapted to a corvair, that fits a fiat 500 experimental airplane.
Don't believe me? I didn't think you would, it's that KIND of thing. :P
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Re: how do hyper pistons work?

Post by Newold1 »

Makes you realize that a lot of special design, metallurgy and development goes into pistons and their types, shapes and usage goes into coming up with the good pistons that work well in their applications. Obviously pistons in a running engine that are subjected to cooling system effects, oiling and lubrication as well as type, and operating characteristics do not heat up and change dimension as they do when put in a toaster and uniformly heated.
Thank god they don't , we would have a lot of messed up engines!
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Re: how do hyper pistons work?

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I think it's like 'the bug in your eye'.
You can go your whole life, never see it, even though it's right there the whole time.
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Re: how do hyper pistons work?

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A stock 1600 can be any where between .0015-.0023 with a wear limit of .008. Just depends on where the manufacture says to measure the piston.
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Re: how do hyper pistons work?

Post by modok »

Right. but that was a completely different kind of piston.
The back side of oil ring groove was open to the inside, and had steel plates cast inside.
That type of piston sometimes uses no taper at all. if there is no taper, then there is no need to specify where to measure!! Makes a lot more sense.

Although, the wear limit of .008 is pretty interesting. :shock: what part of what did they think would wear that much?? OR, that's by the oil ring

But, maybe old things making sense is only because old things were designed by common sense.
i was thinking that about trying to line hone a subaru.....which was a total fail, thinking about fasteners and axle bolts and how an axle bolt is almost always a bad idea. A woman comes in with a telescope, basically wants me to make a new axle. She wants a 2" rod stepped and threaded basically an axle bolt that screws into to the frame. I say no, use a flange. After much inspection we find the original, which is broken off now, was in fact a giant axle bolt. Great minds think alike, and so do normal minds. That may not make a lot of sense to you but it does to me. ARp main studs in a subaru is a stupid idea that won't work, and I can't fix it. But I CAN fix this telescope!!
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Re: how do hyper pistons work?

Post by DrillDawg »

I think the stock piston is measured at the bottom of the skirt and your piston is a low expansion design also, the point is if you give yourself the extra .001 of clearance should not hurt anything, The cyl. usually wears more than the piston, with taper and out of round.
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Re: how do hyper pistons work?

Post by modok »

yeah, I think so too. but I won't think the same after realizing this.
I mean, I'm not going to argue that 'low expansion" is a misnomer......but they actually expand the same with heat.
If a hyper piston of the same general shape can run tighter, it is because it has greater scuff resistance and/or does not get as hot, The metal itself expands the same amount with temp.
It may also mean that forged pistons could run just as tight if you could impart these same properties to them, which is probably possible.
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Re: how do hyper pistons work?

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Hyper pistons were developed to be able to run tighter clearances for better ring seal while being stronger than cast and where the strength of a forged piston is not needed.
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Re: how do hyper pistons work?

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https://www.uempistons.com/installation ... lation.pdf

Look at the top of the second page, air cooled baja, then read just below that....disclaimer
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Re: how do hyper pistons work?

Post by modok »

Yes. KB is awesome.
however, look at the KB motorcycle pistons. some running SQUEAKY tight now.
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Re: how do hyper pistons work?

Post by DrillDawg »

Not sure what your after, maybe call the manufacture and someone who has experience with VW hyper pistons.
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Re: how do hyper pistons work?

Post by groberts101 »

Can't link from phone but a good Google is.. wiseco piston to wall clearance, myths, mysteries, and misconceptions explained.

Just far too many factors involved here to make blanket statements about clearance requirements. Power levels and sustained periods of WOT will change spec's on identical architecture motors.
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Re: how do hyper pistons work?

Post by modok »

Thanks I'll find that

What am I looking for?
I'm looking for is understanding. I want to understand this better than i do.

The piston that started me thinking, is, probably not a good example of anything.
It's not mine. Personally I would scrap it and use what I feel is a better piston for the job, which I even have in stock, actually.
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Re: how do hyper pistons work?

Post by MadBill »

Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
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