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| Home > Help Needed / General Tech Chat > just a quick question about compression ratio sorry! | |||||||
 871 Posts Member #: 2590 Post Whore Croydon |
29th Aug, 2010 at 06:14:00pm
well my engine being a metro 1275 engine 12hA83AA
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 334 Posts Member #: 7169 Gobshite that posts wank videos. Somerset, UK |
29th Aug, 2010 at 09:09:10pm
What's the bore and stroke again ill do the maths quick Gaball said:
Motorsport Engineering Student Project Car 1293 Turbo Mini (on a student budget) On 7th Oct, 2010 apbellamy said:
Carbon but plug? |
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334 Posts Member #: 7169 Gobshite that posts wank videos. Somerset, UK |
29th Aug, 2010 at 09:18:35pm
It's
Gaball said:
Motorsport Engineering Student Project Car 1293 Turbo Mini (on a student budget) On 7th Oct, 2010 apbellamy said:
Carbon but plug? |
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871 Posts Member #: 2590 Post Whore Croydon |
30th Aug, 2010 at 03:29:41pm
everything is standard in the block for the metro engine |
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 9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
30th Aug, 2010 at 03:35:58pm
The problem is that there are plenty of different standards and with out measureing you are just guessing. Look at roberts Vauxhall engine, if he'd have just assumed all standard he'd have melted something.
Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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 8604 Posts Member #: 573 Formerly Axel Podland |
30th Aug, 2010 at 03:40:22pm
On 29th Aug, 2010 Gaball said:
It's (1/2 BORE x pi squared) x STROKE Divide that by the combustion chamber volume and that's it assuming the pistons are flush with dexk Wrong on several counts. (1/2 BORE squared x pi) x STROKE Divide that by the combustion chamber volume, then add 1. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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871 Posts Member #: 2590 Post Whore Croydon |
1st Sep, 2010 at 10:31:23am
right i have done some measuring and i have come up with 10.25cr
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 16540 Posts Member #: 4241 King Gaycharger, butt plug dealer, Sheldon Cooper and a BAC but generally a niceish fella if you dont mind a northerner Rotherham, South Yorkshire |
1st Sep, 2010 at 10:42:53am
By my clac's it's 10.77:1 as the BK450 is is 3.8cc.
On 11th Feb, 2015 robert said:
i tried putting soap on it , and heating it to brown , then slathered my new lube on it 
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334 Posts Member #: 7169 Gobshite that posts wank videos. Somerset, UK |
1st Sep, 2010 at 11:18:48am
Yep sorry got my pi's r's and sqaures mixed up!
On 30th Aug, 2010 Paul S said:
On 29th Aug, 2010 Gaball said:
It's (1/2 BORE x pi squared) x STROKE Divide that by the combustion chamber volume and that's it assuming the pistons are flush with dexk Wrong on several counts. (1/2 BORE squared x pi) x STROKE Divide that by the combustion chamber volume, then add 1. Gaball said:
Motorsport Engineering Student Project Car 1293 Turbo Mini (on a student budget) On 7th Oct, 2010 apbellamy said:
Carbon but plug? |
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871 Posts Member #: 2590 Post Whore Croydon |
1st Sep, 2010 at 11:22:33am
ah great so i need a 6cc decompression plate and all should be well |
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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 |
1st Sep, 2010 at 11:44:11am
On 1st Sep, 2010 Gaball said:
Yep sorry got my pi's r's and sqaures mixed up! and where's the plus one? is that a constant Paul? i have never been taught this so just wondering? Because it's actually (swept volume + combustion chamber volume) all divided by combustion chamber volume. Swept volume is the pi*r^2*stroke or ((pi*d^2)/4 )* stroke. So if you say the swept volume (all the pi bit) is SV and combustion chamber volume is CV, just to make it look prettier, CR = (SV+CV)/CV which you can rewrite as CR= SV/CV + CV/CV Or CR = (SV/CV) +1 Personally I just use a spreadsheet :) EDIT - obviously in my simplified version, combustion chamber volume is the total combustion chamber volume, ie, the actual chamber in the head + piston dish + ring land volume + below deck volume + gasket volume. Another good reason to use a spreadsheet, so nothing is missed. Edited by Rod S on 1st Sep, 2010. Schrödinger's cat - so which one am I ??? |
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8604 Posts Member #: 573 Formerly Axel Podland |
1st Sep, 2010 at 12:05:10pm
On 1st Sep, 2010 blister said:
ah great so i need a 6cc decompression plate and all should be well Dont waste your time, just get a head with 28cc chambers. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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16540 Posts Member #: 4241 King Gaycharger, butt plug dealer, Sheldon Cooper and a BAC but generally a niceish fella if you dont mind a northerner Rotherham, South Yorkshire |
1st Sep, 2010 at 01:08:36pm
28cc head only gives him 9:1, he needs to look at his piston choice too. On 11th Feb, 2015 robert said:
i tried putting soap on it , and heating it to brown , then slathered my new lube on it
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871 Posts Member #: 2590 Post Whore Croydon |
1st Sep, 2010 at 01:45:33pm
cannot change pistons as that would mean taking the block apart and i dont really want to modify the head any more as if i decide to run N/A i would then have to have the head skimmed lots to bring the ratio up
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 3329 Posts Member #: 184 Senior Member Melton Mowbray, Pie Country |
1st Sep, 2010 at 02:10:59pm
What sort of boost are you thinking of running if you are looking for 8:1 CR?
http://www.twin-turbo.co.uk
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16540 Posts Member #: 4241 King Gaycharger, butt plug dealer, Sheldon Cooper and a BAC but generally a niceish fella if you dont mind a northerner Rotherham, South Yorkshire |
1st Sep, 2010 at 02:13:31pm
I was recommedned 8:1 for my suck through charger setup running 12psi On 11th Feb, 2015 robert said:
i tried putting soap on it , and heating it to brown , then slathered my new lube on it
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334 Posts Member #: 7169 Gobshite that posts wank videos. Somerset, UK |
1st Sep, 2010 at 03:50:40pm
Oh so its just a rearangement of the CR= SV+CV all over CV equation :) I get it now
On 1st Sep, 2010 Rod S said:
On 1st Sep, 2010 Gaball said:
Yep sorry got my pi's r's and sqaures mixed up! and where's the plus one? is that a constant Paul? i have never been taught this so just wondering? Because it's actually (swept volume + combustion chamber volume) all divided by combustion chamber volume. Swept volume is the pi*r^2*stroke or ((pi*d^2)/4 )* stroke. So if you say the swept volume (all the pi bit) is SV and combustion chamber volume is CV, just to make it look prettier, CR = (SV+CV)/CV which you can rewrite as CR= SV/CV + CV/CV Or CR = (SV/CV) +1 Personally I just use a spreadsheet :) EDIT - obviously in my simplified version, combustion chamber volume is the total combustion chamber volume, ie, the actual chamber in the head + piston dish + ring land volume + below deck volume + gasket volume. Another good reason to use a spreadsheet, so nothing is missed. Gaball said:
Motorsport Engineering Student Project Car 1293 Turbo Mini (on a student budget) On 7th Oct, 2010 apbellamy said:
Carbon but plug? |
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871 Posts Member #: 2590 Post Whore Croydon |
1st Sep, 2010 at 06:06:55pm
was after running the 10psi which means running the smaller pulley but would not mind getting it running with the standard pulleys which i believe should be 6-7 psi |
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871 Posts Member #: 2590 Post Whore Croydon |
1st Sep, 2010 at 06:06:57pm
was after running the 10psi which means running the smaller pulley but would not mind getting it running with the standard pulleys which i believe should be 6-7 psi |
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