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 11046 Posts Member #: 965 Post Whore Preston On The Brook |
30th Oct, 2008 at 10:18:41pm
11mm, Are they forged? They cant be very light? On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be... So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'... On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........ |
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 (2)[/url] by [url=https://www.flickr.com/photos/150672766@N03/]Rod Sugden[/url], on Fli) 5988 Posts Member #: 2024 Formally Retired Rural Suffolk |
30th Oct, 2008 at 10:53:38pm
On 30th Oct, 2008 Sprocket said:
7mm. Those turbo pistons are tough old boots!! On 30th Oct, 2008 PaulH said:
:lol that they are, On my omegas there is 11mm so from that point of view im not to bad Fook.... I've taken the Hypatecs down to slightly under 5mm to get the dish I wanted..... Does that mean my bang will be biggest :):):) Schrödinger's cat - so which one am I ??? |
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 1849 Posts Member #: 672 The oversills police Oslo, Norway |
31st Oct, 2008 at 07:57:12am
all 4 of mine are also cut with the cut outs at the same place Sprocket |
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520 Posts Member #: 2093 Post Whore Grenoble, France |
31st Oct, 2008 at 06:00:55pm
On 29th Oct, 2008 PaulH said:
Ok guys taughts on this, Attached is a pic of a drawing I have been doodling with, (I relay need to learn CAD) I have just finished Dishing out my pistons and got to thinking is there a possibility of bad flame prop and uneven burn as the piston moves of TDC with the current design (the left hand side of the attached drawing in cross section view) and would I be better radiusing the outside wall (as in the right hand side of the drawing again cross section view) ?? You’re taught greatly appreciated Hi, Sharp edges are sources of pre-ignition as they heat more. So to avoid (it's also true for pockets and engine bottom to head mismatch). The right-hand is better. High compression pistons usually have squish areas all around the top to make mixture go toward the middle of the chamber. This increases turbulences (and thus flame propagation speed, thus combustion stability and knock resistance and thus overall engine efficiency). This is not necessarily useful with series-A heads which have huge squish areas, if used with flat pistons. It's still useful on turbo engines to lower CR and keep chamber compact. Flame prop depends on turbulence, local mixture composition and wall heat transfer. I don't think rounding corners would affect the flame propagation, but it will certainly affect your ability to tune the engine. I think the best is to match the shape on the piston dish to the chamber in the head. The main goal is to avoid chamber having uneven height. Every time the chamber height changes so does the instant pressure. The more the pressure, the more probability to create a knock condition. The best chambers (F1) have a very regular height and are round (looking from the top) in order to avoid any pressure dispersion. Edited by alpa on 31st Oct, 2008. std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm |
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 6274 Posts Member #: 509 Post Whore Isle of Man |
1st Nov, 2008 at 12:48:01am
On 31st Oct, 2008 alpa said:
Hi, Sharp edges are sources of pre-ignition as they heat more. So to avoid (it's also true for pockets and engine bottom to head mismatch). alpa you'll love this then! : 
see http://www.turbominis.co.uk/forums/index.php?p=vt&tid=249407 "Turbo's make torque, and torque makes fun"
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520 Posts Member #: 2093 Post Whore Grenoble, France |
1st Nov, 2008 at 06:38:23am
It's interesting to note that it's melted on the edge side.
std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm |
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They are just made slightly oval:)| Page: |