Bored, so I nerded out on rad/stroke ratio

[rocco16v at netzero.net (L F)]

Actually, longer crank throws (more stroke) will increase piston acceleration/speed at the same rpm.  Increasing rod length (decreased rod angularity) will decrease piston acceleration/speed.
You may have gotten the two mixed up.

Larry
  ----- Original Message ----- 
  From: Allyn 
  To: Ron Pieper ; scirocco-l@scirocco.org 
  Sent: Saturday, January 31, 2004 4:54 PM
  Subject: Re: Bored, so I nerded out on rad/stroke ratio


  ok, i get how the piston accel is lower with longer throws, but i always
  thought the main limit for the bottom end was the mean piston speed. issue
  being getting enough oil to keep the rings cool and the skirt lubed.
  Al

  ----- Original Message ----- 
  From: "Ron Pieper" <rapieper@yahoo.com>
  To: <scirocco-l@scirocco.org>
  Sent: Saturday, January 31, 2004 12:25 PM
  Subject: Bored, so I nerded out on rad/stroke ratio


  > Momma wanted to watch her Thursday night TV, and the kids were in bed, and
  it was too cold to work
  > in the garage, so with nothing else to do, I figured I'd see what the the
  scoop was behind varying
  > the con rod/stroke ratio.
  >
  > Gotta DIY, being me, so I did some trig in Excel and a little (very crude)
  derivation, I came up
  > with this:
  >
  > http://scirocco.dhs.org/cheapassron/misc/rodratio.jpg
  >
  > No units (AFA ft/s/s, etc.) but I do believe it works as a visual aid.
  The center of the graph is
  > TDC.  Obviously something is wrong with the Y axis offset, but I think the
  shape is right.
  >
  > This is not new news, but from what I see, it tells me that longer
  rod/stroke ratios lead to
  > overall lower piston acceleration rates (meaning less stress and higher
  revability?) and later
  > peak accleration (meaning compensations in cam (less overlap required?),
  intake, and exhaust
  > design, but what exactly I don't know).  Anyhow, some of you MatLab gurus
  may want to pick up on
  > this and discuss what positive impacts one could make on a NA engine.  Oh,
  and fix my spreadsheet
  > (verrrry crude) http://scirocco.dhs.org/cheapassron/misc/piston_speed.xls
  >
  > Now, back to your normally scheduled discussions...
  >
  > =====
  > Cheapass Ron
  > '81 Scirocco S - "Victor Jr."  7SM
  > (2.0L 16V, GL 4-speed w/ Quaife installed, Megasquirt coming...)
  >
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