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| − | ==Beyond DCR==
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| − | There is a limit to what DCR can do. Other concepts have been developed that take this a step (or several steps) further than what DCR is able to accomplish.
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| − | *[http://victorylibrary.com/mopar/cam-tech-c.htm#factor Cam Timing vs. Compression Analysis] is an "advanced" formula for looking at the relationship of SCR vs. DCR. In the text the author uses "'''''supra'''''" a lot, it basically means "more info above".
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| − | *[http://horsepowerchain.com/ The Horsepower Chain] attempts to put things into a mathematical prospective, and breaks the 4-stroke engine's cycles into 7 distinct segments.
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| − | ==Online calculators==
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| − | ===Static CR===
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| − | *[http://www.wheelspin.net/calc/calc2.html SCR calculator]
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| − | ===Dynamic CR===
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| − | *[http://www.empirenet.com/pkelley2/DynamicCR.html Dynamic compression calculator] by Kelly
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| − | *[http://www.uempistons.com/calc.php?action=comp2 Dynamic compression calculator] by KB
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| − | *[http://www.wallaceracing.com/dynamic-cr.php Wallace Racing DCR calculator]
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| − | *[http://www.rbracing-rsr.com/comprAdvHD.htm RSR DCR calculator]
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| − | {{Note1}} Some dynamic compression ratio calculators (like KBs) ask for an additional 15 degrees of duration be added to the IVC @ 0.050" lift point figure. This works OK on older, slower ramped cam lobes, but the faster lobe profiles may need to have 25 degrees or more added to be accurate.<br>
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| − | {{Note1}}If the intake valve closing (IVC) point isn't known, it can be calculated:
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| − | # Divide the intake duration by 2
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| − | # Add the results to the lobe separation angle (LSA)
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| − | # Subtract any ground-in advance
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| − | # Subtract 180
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| − | This result does not need to have any amount added to the IVC point, like the KB calculator calls for.
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| − | ==DCR and pump gasoline==
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| − | It's worth mentioning that 8.5:1 DCR is considered to be the maximum for iron heads and 92 octane fuel (MON + RON divided by 2).
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| − |
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| − | ==SCR vs. DCR vs. duration==
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| − | The following are different static compression ratios (SCR) with a 3.48" stroke and different camshaft intake closing points @ 0.050" tappet lift on Keith Black's dynamic compression ratio calculator. The calculator, starting at 8.25:1 SCR. The dynamic compression ratio (DCR) has been kept at just over 8.0:1, a figure that is acceptable for use with today's pump gas with a little cushion:
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| − | *Static CR....Intake closing point @ 0.050"....Dynamic CR.
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| − | *8.25........10* ABDC......8.010........................................................................................................
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| − | *8.50........20............8.012........................................................................................................
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| − | *8.75........27............8.022........................................................................................................
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| − | *9.00........33............8.018........................................................................................................
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| − | *9.25........37............8.061........................................................................................................
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| − | *9.50........42............8.029........................................................................................................
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| − | *9.75........46............8.016........................................................................................................
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| − | *10.00.......49............8.038........................................................................................................
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| − | *10.25.......52............8.043........................................................................................................
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| − | *10.50.......55............8.029........................................................................................................
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| − | *10.75.......57............8.069........................................................................................................
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| − | *11.00.......60............8.022........................................................................................................
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| − | *11.25.......62............8.038........................................................................................................
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| − | *11.50.......64............8.042........................................................................................................
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| − | *11.75.......66............8.035........................................................................................................
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| − | *12.00.......68............8.017........................................................................................................
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| − |
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| − | ==Disclaimer==
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| − | Now, it's unclear where these Keith Black DCR calculator dynamic compression ratio readings are taken; at cranking rpm or at max efficiency rpm. According to the DynoSim software, maximum cylinder pressure is made at or near the torque peak. So, the fact that a motor is not detonating at low rpm does not mean that it will not detonate at, or close to, the torque peak.
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| − | These numbers may not mean anything at all, but they do illustrate that you cannot just pick a cam out of thin air like a lot of fellows do and expect it to work best for your particular combination.
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| − | <br><br>
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| − | {{youcanedit}}
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| − | [[Category:Engine]]
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| − | [[Category:Cylinder head]]
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