Hypatec / Hypatech pistons
Turbo Mini Forums

please take away that sharp edge on the ridge above the dish though.

indeed! is hould have done that wile it was still clocked up on the chuck really, thought of it soon as ii took it off

which piston is that colin ,is it 23512 ergo 19648 (made up nos ) or such like ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

cant remember off the top of my head but its the standard deep 12cc dish turbo piston. You could possibly get it to 18cc total without weakening it beyond use

Edited by Sprocket on 7th Nov, 2008.

oh, also slipping on the the topic of mega pistons, i spotted this the otherday.

hmmm, weird, maybe this will work...

http://www.minimania.com/web/displayID/1705/ArticleV.cfm

Edited by Joe C on 8th Nov, 2008.

linky no work

+1 (or even +1000000 !)
What's the smell of the melted alu ? :)

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Just out of curiosity... why do you guys leave the outer rim on the crown so tall? It would seem that you could knock that down as well and not have to go as deep. In doing that you would also get rid of a "squish" point.

Squish is what you want to try and maintain. Squish promotes turbulance of the mixture in the chamber resulting in a better burn

I stand corrected... for some reason I thought "squish" could potentially lead to detonation if it is too tight or a hot spot. Taking a look in my book... it says "squish volume is considered scared and should not be tamper with." Just for reference squish volume is a rim about .3" to .4" wide around the chamber, and ~.040" thick. Apparently, the idea is to push the charge toward its center as the piston achieves TDC. It also states, that a reasonable rule of thumb would require the top thickness to be at least 6% of the bore... everyone here seems to meet that rule.

Read a different book! Bell, Yunick etc.

I don't have my stuff here (and for a long time), so I can not check.
I'm not sure a round squish area on pistons is a good idea on A-series. I'm pretty sure in some areas the top of the piston will be below the chamber cavity of the head. This will just create a narrower chamber area, but no squish. And this is bad for knock resistance.
I think you should match squish areas to the shape of the combustion chamber in the head.
And please remove sharp edges inside the pistons !

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Edited by Sprocket on 11th Nov, 2008.

I was thinking along the same lines the other day,

I dont think its bad piston design, its bad head chamber design

the thing is the heart shaped chamber has been around for longer than I have been on the planet, and has been see to give results so where is the problem?

The other thing to consider is if having all the chamber/ dish on one side of the piston, will that not put a tilting force on the top of the piston on ignition?

We've discussed that a bit in another thread, I gave my point of view on this page:
http://www.turbominis.co.uk/forums/index.p...id=252268&fr=25

No doubt it's a bad chamber design. Unfortunately pistons work together with the head.
On many old engines like Porsche v8, Peugeot 205GTI, R5 and other crappy designs the squish area was in front (on the opposite side) of the plug, pushing the mixture toward the plug. This was working well even turbocharged.
Instant pressure distribution is important for not burned fraction of the mixture, because it defines hot spot distribution and thus knock resistance. A burned mixture pushes everywhere, at least I've never seen any paper about related problems. That's why high pressure areas become even worse as mixture temperature raises with pressure, and start pre-ignition.

Edited by alpa on 11th Nov, 2008.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

RObert tarzwell and a few other racers I know always make and design their own dish and make them a mirror of the chambers...

I've just got some 73mm Hypatechs from minisport Asutralia. Great quality pistons. Quick question for those that have also bought them. The oil control support wavy ring, when fitted to the groove on the piston it won't close right up. I mean, when the ends of the wavy ring meet, the ring is still quite proud of the groove, is this right?

I don't remember if mine looked the same when I assembled them - possibly wouldn't have noticed as the very thin parts of the oil control ring above and below the wavy bit obviously stick out anyway - but the combined package (wavy bit and the two thin bits) compressed no problem with a conventional piston ring compressor.

I assume the "waves" just get shorther as the ring is compressed.

EDIT - typo

EDIT 2 - I should add that I measured the gaps of the two thin bits (and of both the upper compression rings) before fitting the package but obviously you cant measure the "gap" of the wavy bit because it's length can/will change. I was actually impressed by the quality of the Hastings rings supplied, none of the gaps needed adjusting.

Edited by Rod S on 29th Mar, 2010.

Schrödinger's cat - so which one am I ???

I really don't want to sound dumb, but the pistons are slightly smaller than 73mm and the rings expand to to fill the size of the bore. I'm sure mine lined up nicely when they slotted down the bores...

Most of the friction in an engine comes from the oil ring.

Obviously check the gaps of the scraper rails and compression rings, otherwise, dont worry about it :)