Cam and compression ratio compatibility

From Crankshaft Coalition Wiki
Jump to: navigation, search
(Undo revision 3477941 by 164.90.34.153 (talk))
 
Line 1: Line 1:
 +
 +
 
==Matching cam to compression ratio==
 
==Matching cam to compression ratio==
 
Sometimes it's difficult trying to explain to fellows who are new to hot rodding that you have to match the characteristics of the camshaft to the static compression ratio of the motor along with the operating range where the cam makes power. The camshaft is not a stand-alone piece. It must be coordinated with other motor and drivetrain parts in order to arrive at a combination of parts that will all work together toward a common goal.
 
Sometimes it's difficult trying to explain to fellows who are new to hot rodding that you have to match the characteristics of the camshaft to the static compression ratio of the motor along with the operating range where the cam makes power. The camshaft is not a stand-alone piece. It must be coordinated with other motor and drivetrain parts in order to arrive at a combination of parts that will all work together toward a common goal.
Line 55: Line 57:
 
|-
 
|-
 
|}
 
|}
==STOP RIGHT HERE, THIS IS INCORRECT==
 
What size stroke is in these engines that these figures above are suppose to represent.  You can't believe that an engine with a 3.000" stroke is going to have the same RPM range as an engine with a 4.500" stroke, using the same duration cam?  It won't and all of these generalizations are ridiculous.  The duration of a camshaft is determined by the Mean Port Velocity and the Mean Piston Velocity, which is determined by the Stroke and RPM.  You're trying to fill the cylinder at a given RPM, and in order to due that you need to control the Mean Port Velocity during the induction process.  Controlled Induction!  Compression does not have anything to do with determining the correct cam duration for your engine and desired Peak HP RPM? 
 
((Mean Piston Velocity FPM / Mean Port Velocity FPM) * PI), and 2 more calculations give you the valve seat duration. You can find it in Controlled Induction.
 
 
 
==Additional reading/engine theory==
 
==Additional reading/engine theory==
 
{{Note1}}  
 
{{Note1}}  
Line 109: Line 107:
 
*[http://www.uempistons.com/calc.php?action=comp2 Dynamic compression calculator] by KB
 
*[http://www.uempistons.com/calc.php?action=comp2 Dynamic compression calculator] by KB
 
*[http://www.wallaceracing.com/dynamic-cr.php Wallace Racing DCR calculator]
 
*[http://www.wallaceracing.com/dynamic-cr.php Wallace Racing DCR calculator]
{{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.
+
{{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 nnbfigure. 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.
  
 
===Cam phasing===
 
===Cam phasing===
Line 164: Line 162:
 
[[Category:Camshaft]]
 
[[Category:Camshaft]]
  
 +
<pre style="border:none;">
 
General Application Chart *
 
General Application Chart *
 
Advertised
 
Advertised
Line 179: Line 178:
 
290°+ 3.73+ 3400-8000
 
290°+ 3.73+ 3400-8000
 
10.5 to 12 3500+
 
10.5 to 12 3500+
 +
</pre>

Latest revision as of 07:00, 17 July 2023

Personal tools
Namespaces
Variants
Actions
Navigation
Categories
Toolbox