2 Cycle Setup on a Pipe

[Lance Van Nostrand]

Randy,
If these timing numbers are correct then a first approximation of pipe
length can be estimated from the pressure wave propagation timing.  Other
factors are used for fine tuning, but this sets the tuning resonance to a
multiple of 4.88 inches nominally. This is really an ugly simplification,
but it puts you in the ballpark. Using this number you could tune the length
for 24.4inches (4.88 x 5) or 29.3 inches.  This explains both answers you
received below.

--Lance

----- Original Message ----- 
From: "Brian Young" <b4598070 at yahoo.com>
To: <discussion at nsrca.org>
Sent: Wednesday, March 31, 2004 12:55 PM
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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