Variable Restrictiveness Exhaust - Meet Mr Helmholz

[Gary Derian]

Two stroke pipes are tuned by injecting water.  I think its common in
personal water craft.  They just use a constant stream.  I think there may
be a little to be gained by timing the water but that would be a small
improvement, maybe using less water for the same effect, compared to using
the water in the first place.

This talk of fancy tuning is interesting and certainly improves the power
per displacement but my question is does all this work actually make a
better vehicle.  Isn't it easier to just use a larger engine with
appropriate gearing to achieve the same power and economy without all the
extra parts?

For sure there is some small fuel economy gain in city driving with a small
displacement engine because it uses less fuel at idle.  But in cruise mode
or WOT, specific power is not really affected by fancy tuning.

Gary Derian <gderian at oh.verio.com>


> The majordomo deleted portion proposed active acoustical tuning using a
> "microphone" or a sensitive pressure sensor well filtered and positioned
near
> the valve to observe the exhaust acoustical pressure and in conjunction
with a
> camshaft angle sensor, we would have the feedback mechanism to actively
> measure and time the arrival of the negative going pulse.
<big snip>
> Since the sole purpose of the water is to vary the resonance by varying
the
> temperature it becomes very interesting on how to administer the water.
> Probably the simplest  is to vary the temperature of the gas in the
collector.
> But would timed injection into the exhaust port just before the exhaust
valve
> opens be more effective or just trailing the major pulse or perhaps even
into
> the exhaust pulse itself.  ????  Floors open.
>