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The BMW Range
5 Series
E34
Local M50 engines secretly built for tarbo?
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<blockquote data-quote="fandango" data-source="post: 462385" data-attributes="member: 3194"><p>The pressure in a compression test can be calculated using the formula below:</p><p></p><p>Compression ratio X 14.7 psi</p><p></p><p>14.7 psi is the nominal atmospheric pressure at sea level and you multiply that times the number of times it's volume is compressed (compression ratio).</p><p></p><p>Example:</p><p></p><p>Compression ratio for the M52 engine is 10.2:1</p><p></p><p>Compression test pressure should nominally be 14.7 x 10.2 = 149.9 psi</p><p></p><p>For the M50 the compression ratio is 10.5:1 so:</p><p></p><p>14.7 x 10.5 = 154.4 psi</p><p></p><p>You'll get some variation readings due to engine tolerances, altitude, etc.</p><p></p><p>If you were in Denver at 5,000 ft altitude the atmospheric pressure is 12.23 psi so your compression reading would be:</p><p></p><p>12.23 x 10.5 = 128.4 psi</p><p></p><p>If you were really high in the mountains at 10,000 ft the pressure would be 10.1 psi so your compression reading would be:</p><p></p><p>10.1 x 10.5 = 106 psi</p><p></p><p>Now you know why your performance falls off at higher altitudes..............</p><p></p><p>(source: bimmerfest.com)</p></blockquote><p></p>
[QUOTE="fandango, post: 462385, member: 3194"] The pressure in a compression test can be calculated using the formula below: Compression ratio X 14.7 psi 14.7 psi is the nominal atmospheric pressure at sea level and you multiply that times the number of times it's volume is compressed (compression ratio). Example: Compression ratio for the M52 engine is 10.2:1 Compression test pressure should nominally be 14.7 x 10.2 = 149.9 psi For the M50 the compression ratio is 10.5:1 so: 14.7 x 10.5 = 154.4 psi You'll get some variation readings due to engine tolerances, altitude, etc. If you were in Denver at 5,000 ft altitude the atmospheric pressure is 12.23 psi so your compression reading would be: 12.23 x 10.5 = 128.4 psi If you were really high in the mountains at 10,000 ft the pressure would be 10.1 psi so your compression reading would be: 10.1 x 10.5 = 106 psi Now you know why your performance falls off at higher altitudes.............. (source: bimmerfest.com) [/QUOTE]
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Local M50 engines secretly built for tarbo?
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