2 Cycle Setup on a Pipe

[Dean Pappas]

Hello Randy and Bob,
The pipe length from piston face (the plane of the exhaust port) to the reflector baffle is approximately proportional to the exhaust timing. The suggestion to start by shortening the 160 pipe by 0.5" to 1"  Dave gave you is based on this, and his running of both engines. You do not want to shortenn for maximum ground RPM, you want to start long, and fly. After verifying the "correct" needle setting, try a long 5-degree full throttle dive. If the engine gurgles rich, shorten a bit, and try again. When the engine no longer richens, in the 5 degree dive, stop. Any further shortening sacrifices flexible running characteristics for only the tiniest real horsepower inprovement. 
Dean

-----Original Message-----
From: Brian Young [mailto:b4598070 at yahoo.com]
Sent: Wednesday, March 31, 2004 1:55 PM
To: discussion at nsrca.org
Subject: Re: 2 Cycle Setup on a Pipe


Randy Im at 26.5 from the exhaust flange right now.
The 1.60 runs fine at this length, but im only getting
7700 rpm on a 17x12 which I think is low.

I had suggestions of 27 inches for a target from the
1.45, less about .5"-1" for the 1.60. But on Ed
Hartleys website I notice someone running as long as
30". 

FWIW the exhaust timing I measured on the 1.60 is 140
degrees, and on the 1.45 is 147.

--- randy10926 at comcast.net wrote:
> Does anyone else have the ppe lenght for the Webra
> 160?  Hos much change would be need to replace my
> 145 with a 160.
> 
> Randy
> > Don't know, Randy.  I don't know the timing of the
> Webra 160 and no one has
> > let me borrow one.  I own the Webra 145, OS140,
> Mintor 170 and regularly use
> > these in testing.
> > --Lance
> > 
> > ----- Original Message ----- 
> > From: <randy10926 at comcast.net>
> > To: <discussion at nsrca.org>
> > Sent: Tuesday, March 30, 2004 3:17 PM
> > Subject: Re: 2 Cycle Setup on a Pipe
> > 
> > 
> > > Is the pipe length for the Webra 160 the same as
> for the Webra 145?
> > >
> > > Randy
> > > > Ditch the MC carb during testing and put a
> regular 1.45 carb on it.  The
> > > > bench mount it.  I have been testing AeroSlave
> carbon pipes for a year
> > now
> > > > and have a great setup for quickly getting
> tuning length and rpms.  I
> > have a
> > > > "trombone" made from two pieces of silicon
> coupler with a short length
> > of
> > > > aluminum header pipe in between. By starting
> with everything extended to
> > the
> > > > extremes and sliding the whole mess together I
> can watch a tach and take
> > > > readings real time.  Takes about 5 min to get
> the numbers and then setup
> > the
> > > > flying lengths.
> > > > --Lance
> > > >
> > > > ----- Original Message ----- 
> > > > From: "Brian Young" <b4598070 at yahoo.com>
> > > > To: <discussion at nsrca.org>
> > > > Sent: Monday, March 29, 2004 3:16 PM
> > > > Subject: 2 Cycle Setup on a Pipe
> > > >
> > > >
> > > > > I have recently been tuning on my exhaust
> and have a
> > > > > basic understanding but want some more
> information.
> > > > >
> > > > > I have a Webra 1.60 w/ MC carb and a Webra
> pipe w/ a
> > > > > disk baffle.
> > > > >
> > > > > Im gradually shortening this pipe setup
> hoping to hit
> > >
> > > > > the correct length. The problem I find with
> this setup
> > > > > is the MC carb doesnt lend itself to a test
> stand
> > > > > since the mixture is servo controlled. So I
> shorten
> > > > > pipe and fly, shorten and fly.
> > > > >
> > > > > The thing Im most curious about is if you
> had a setup
> > > > > no one else has how do you determine a close
> first
> > > > > guess for the pipe length if you want to cut
> down the
> > > > > trial and error? I had a starting point but
> was just
> > > > > puzzling over this.
> > > > >
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