[Vwdiesel] ECO -- VW ----( Hagars ECO -- Bunny Bondo )

Val Christian val at swamps.roc.ny.us
Thu Apr 14 12:58:58 EDT 2005


I'll give short lip service to the topic.  You'll need to tune so that you 
can load the intake on once cyl when the other has a back wave from a 
closing valve.  You also want to look at the total system resonance to 
reduce noise.  

I can't cookbook it for you, because it's been a long time since I've done
this stuff.  The reference text I would use is Acoustics, by Beraneck.

I'd probably get the rest of the system optimized first, and make the 
inlet timing issues the final embelishment.  I don't know exactly what
toolkits would be available right now.  Years ago, NASTRAN facilitated
modeling.  I'd probably look at the toolkits for MATLAB.  Simulink
might be a help, but you're going to want to model pressure and flow,
through different speeds.  

My acoustic life was horn design, and some acoustic modeling.  This stuff
is a little different, but it's still just like designing a ducted port 
type loudspeaker system.

If anyone uses a more current Acoustics text, I'd be interested.  Beranek's
book is about 50 years old.


> Bob,
> In my fixed speed 1800 RPM genset application with a NA 1980, 1.5 D, I am
> after absolute minimun fuel consumption possible.  I thought of
> experimenting with tuned intake runners as you mention as a way of improving
> power and efficiency (lower fuel use).  Any idea of the mathematical formula
> to calculate runner length?  Is the wave propagation at the speed of sound.
> 1140 ft/sec and independent of flow velocity in the pipe?
> I am also interested in the potential benefit that advancing the camshaft
> may have on my application as well, although I recently read that a whole
> belt notch on the cam gear will cause valve piston collisions.  Not much
> room upstairs in these high compression engines.  I'm used to working on
> obsolete (by that I mean pretty much all of them now) gasoline engines with
> auditorium sized head volumes.
> Rob
> ----- Original Message -----
> From: <slatersfb at aol.com>
> To: <vwdiesel at vwfans.com>
> Sent: Thursday, April 14, 2005 10:38 AM
> Subject: [Vwdiesel] ECO -- VW ----( Hagars ECO -- Bunny Bondo )
> > Check out the long intake runners on N/A motor. These are a tuned length
> to create positive wave pressure at the time intake valve opens. Wave tuning
> actually stuffs incoming charge into cylinder, rather than relying on vacuum
> to suck it in.
> > Waves are created in runner when intake valve slams shut on incoming
> charge, and another when intake opens. These waves travel backwards, up
> through runner and are reflected back down from the open end. The length of
> runner determines the rpm at which the positive wave arrives at intake valve
> opening.
> > N/A two stroke motors barely run without wave tuning in the form of an
> expansion chamber.
> >
> > Bob
> >
> >
> > *********
> >
> > And opening that intake
> > valve at 5 psi overpressure is different --- than opening it at a slight
> > underpressure.
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