Variable Restrictiveness Exhaust

[GARY]

1)  
Gary, 
can you elaborate on how that muffler varies?  


Gary Derian wrote:
> 
> Adding backpressure just for the sake of it won't improve low speed torque.
> Having small diameter ports which happen to add backpressure will.  Its not
> the backpressure that improves torque.  Its the low rpm tuned components
> that do.  Now, having a variable restrictor that quiets the car when
> cruising is a good idea.  The new Nissan Maxima has such a muffler.
> Mitsubishi 3000's have had them in the past.
> 
> Gary Derian <gderian at oh.verio.com>
> 
> > Ord Miller wrote:
> >
> > >I use high flow cats.  For the 1 or 2 HP difference, I really don't think
> > >it's worth the risk of legal problems or injuring my environmental
> > >consience. ;)
> >
> > >On the other hand, I am wondering if I could improve low rpm torque if I
> > >could add a variable restrictor??
> >

2)
On the same note, I am under the impression that the length of the
intake tract (air cleaner ducting plus manifold) is instrumental in
tuned intake.  I vaguely understand the principal, something to do with
the length of the wave at a given frequency of intake suck and how that
length is resembled in the intake tract.

So as I understand it, an intake is tuned to a specific rpm (and
multiples and fractionals of same rpm or frequency) by the length of the
intake tract.  This puts the harmonic frequency of the tract at the same
frequency of the the resonance of the air flow.   I am not really
considering volume, just length.  I'll get on to my question, but I
need  to  know if I am correct so far.

If I intervene in that tract by adding a duct (ram air) in a wye
configuration, will I be changing the tune.  I guess I would but I
somehow think that if I "wye in" rather than replace I will be
conserving some of the characteristics that I would have eliminated if I
cut off the existing tract.

3)  
I am trying to decide the best way to dampen the signal from my Knock
Sensor (the Subaru). The resistance of the KS is 520K ohm.  The ECU
appears to be sending about two to three volts D.C. to the Knock Sensor,
but I don't know if that remains constant throughout operation.

What do you guys think of a first resistor in series to dampen output
along with a second resistor paralleling the seriesed KS and first
resistor to make the overall resistance/impedance 520K ohm?  or using a
diode to allow the D.C. monitor current to pass while offering
resistance to the KS generated signal.  I thing a diode would filter the
KS A.C. signal into D.C. and cause a problem.  Any other ideas?

Thank you for your attention folks!

-- 
GARY       mailto:hobiegary at earthlink.net