[NSRCA-discussion] 2C Pipe vs Muffler

[David Lockhart]

Jeff,

I generally break in every 2C engine on a muffler before adding the pipe.  There is not a specific answer to your question - it depends on many variables, such as the timing of the engine, the design of the muffler, the design of the tuned pipe, how aggressively the tuned pipe is tuned, etc.

I do not know of a readily available muffler for the big 2Cs in the US at this time.  The Bolly 480 and 590s were among the best, as is a muffler I picked up from Jerry Budd from Stefan Fink years ago (very light alum, I believe it was made by Graeber in Germany).

If you were to look at a common pattern 2C like the OS140RX running mild/moderate fuel and compression at say 8000 RPM, adding a pipe could add no RPM (but substantially more torque from maybe 3000-4000 and up), or maybe as much as 400 RPM on the top end (and more unload in the air).  The real trick is matching up engine timing (porting), pipe design, and tune length for the RPM range you want to run in.  You can certainly gain more than 400 RPM with the addition of a pipe, but realistically for pattern, you won't see much more than 200-400 RPM (or 1" of pitch or 1" of diameter at the same RPM) without compromising torque, throttle response, and consistency over varied weather conditions.

Regards,

Dave Lockhart
DaveL322 at comcast.net
 

----- Original Message ----- 
  From: jeffghughes at comcast.net 
  To: NSRCA Mailing List ; nsrca-discussion at lists.nsrca.org 
  Cc: Rcmaster199 at aol.com 
  Sent: Monday, March 06, 2006 8:59 PM
  Subject: Re: [NSRCA-discussion] 2C Pipe vs Muffler


  So you are saying you have tried a comparison of a tuned pipe vs a muffler back to back? Any data?

    -------------- Original message -------------- 
    From: Rcmaster199 at aol.com 

    In a message dated 3/6/2006 6:57:30 PM Eastern Standard Time, jeffghughes at comcast.net writes:
      was going through the data on Ed Hartley's 2 stroke page and noted that there is virtually no difference between a piped OS1.40 and a muffled OS1.40 for the prop sizes being used.  I assume that is because to get a nice linear throttle curve on a pipe, the pipe is deliberately set too long for peak horsepower. My question is why run a tuned pipe at all if you are going to set it too long for peak power?. Has anyone run back to back tests with same engine and plane with a pipe vs a muffler to see if there is truly a difference in power or feel?

    Yes and there is

    MattK


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