[NSRCA-discussion] Engine tuning info

[John Pavlick]

Karl,
 Thanks for the info. I never put a degree wheel on a model engine so this is interesting to say the least. I'm surprised that model 4-strokes have no overlap. Hmm. You'd think that something like the YS 170 could benefit from that. I don't have as much tuning experience with 2-strokes as I do with 4-strokes (motorcycles). I'd like to do some experiments with model engines now...

John Pavlick
http://www.idseng.com


  ----- Original Message ----- 
  From: Karl G. Mueller 
  To: jpavlick at idseng.com ; General pattern discussion 
  Sent: Thursday, November 06, 2008 7:19 PM
  Subject: Re: [NSRCA-discussion] Engine tuning info


  John,

  Most of the 2C sport engines to be used with a muffler are timed
  at about 145-148º exhaust down time.
  On most of the .60 to 1.60 size, to get the benefit of the supercharging
  effect from the pipe, I increase the exhaust downtime to 155-158º, without
  changing the intake timing, except for some directional porting for better 
  scavenging effect. This all will not decrease a reliable idle.
  I believe that the pylon engines are ported to 170º exhaust down time and 
  on those you are not looking for a reliable low idle. 
  Never tried any work on 4 strokes. To get any benefit from a pipe on those
  you would have to have overlapping valve timing, which none of our model
  4 stroke engines have.

  Regards,

  Karl G. Mueller
  kgamueller at rogers.com

    ----- Original Message ----- 
    From: John Pavlick 
    To: nsrca-discussion at lists.nsrca.org 
    Sent: Thursday, November 06, 2008 5:02 PM
    Subject: [NSRCA-discussion] Engine tuning info


          Has anyone taken the time to measure the port timing of various model airplane 2C engines? Specifically the OS140 and 160? Also, if anyone has cam profiles + index info for the YS 160 and 170 4C motors I'd be interested in that as well.

          John Pavlick 



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