Date: Fri, 2 Mar 2001 13:42:21 -0700
Reply-To: Mark Keller <kelphoto@ISLANDNET.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Keller <kelphoto@ISLANDNET.COM>
Subject: Re: Headers advantages
Content-Type: text/plain; charset=us-ascii
Greg,
Right now I'm contemplating a dual cat setup, and just tune so that each O2
sensor read close to each other then connect them to the same lead. I feel this
will allow for smaller pipes and mufflers, while allowing the cat to be
basically oversized, since each one only has half the exhaust stream.
Is there a torque graph showing RPM and length for optimum torque.
Alternatively, the specification of the 2.1 maximum torque of 117 ft lb is
around 3100 Rpm..
Sincerely,
Mark Keller
91 Carat.
Fetner Greg wrote:
> Well, looking at the exhaust system on my 85 vanagon, you have a front pipe
> connecting RH and LH front cylinders and a rear pipe connecting the RH and
> LH rear cylinders. These two pipes converge at the LH side of the engine
> and go into the intermediate pipe that next goes into the cat-con then
> muffler. So...it looks like a header system except the pipes (from each
> cylinder) are not "equal length" which is what most header systems shoot for
> in design. The equal length of each pipe allows for "tuning" the engines
> output by varying the pipe (known as primary pipe) length. Longer is torque
> at low rpm and shorter is torque at higher rpm. If we had a small block
> Chevy our choices would be much greater, but, since we drive vanagons, we
> have the S&S and maybe a couple others. As for quiet, pipe wall thickness
> has a lot to do with this. Thin wall pipes ring like a bell with each
> exhaust pulse...thicker pipe dampens the sound much better. I don't know if
> the coatings help but there are "header wraps" (like an ace bandage) that
> help with noise while increasing performance through insulation (keeps
> exhaust gasses hotter so they flow faster).
>
> > -----Original Message-----
> > From: Mark Keller [SMTP:kelphoto@islandnet.com]
> > Sent: Friday, March 02, 2001 10:56 AM
> > To: Fetner Greg; Vanagon Mailing List
> > Subject: Headers advantages
> >
> > Thanks Greg for the nice information regarding header length to
> > advantages.
> >
> > Do you have a recommendation for someone looking for a quiet muffler and
> > header setup. It seems that everyone posts the noise level increases
> > with whatever they do.
> >
> > My main concern is increasing power in the 3100 -3400 RPM range, this is
> > where the Automatic's stall convertor hooks up, and speed is above 48
> > mph, where aerodynamic force becomes effective. This in my opinion is
> > the flat spot in my 91's power range.
> >
> > Also the stock vanagon system, except your comments, seems to be of a
> > header type construction?
> >
> >
> > Sincerely,
> >
> > Mark Keller
> > 91 Carat, and watching the exhaust system near it's end of natural life
> >
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