Hi all.
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Just want to check I'm not going mad.
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Working comp ratios out and my math doesn't seem to add up.
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Stock comp ratio is meant to be 9.4:1 apparently.
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I've done
8.1cm bore
8.2cm head gasket bore
0.12cm crushed head gasket thickness
7.7cm stroke
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Pi 3.142
Piston deck clearance 0.05cm
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(Did deck height
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(191mm)- conrod length
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(122mm)
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- comp height
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(30mm)
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- crank throw ie stroke/2
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(38.5mm)
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So 191-(122+30+38.5)
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= 0.5mm or 0.05 as cm clearance.
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Bore area
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(bore/2)
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*
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(bore/2)
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* pi
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= bore area.
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So 51.536655cm
Gasket bore area
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(basic same calc as above)
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= 52.81702cm
Stroke cc is bore area
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* stroke
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= 396.8322435 cc
Gasket bore area
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* gasket thickness
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= 6.3380424 cc
Piston deck clearance
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* cylinder bore
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= 2.57683275 cc
Head is 36 cc
Apparently stock bigport piston cc is
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-2.5
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So add all volumes
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(cc) up and divide by stroke cc.
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This gives 439.2471187 divided by 42.41487515 which is 10.36:1 compression ratio.
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Is my math wrong or alleged advertised stock piston cc wrong as stock comp is meant to be 9.4:1.
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For that stock ratio piston cc would have to be between 2cc
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& 2.4cc If my calc is correct.
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Any input anyone.
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