LML,  

I checked the numbers for the tuned exhaust explanation I offered
yesterday and found that I had it wrong.  

At 2600 rpm each exhaust valve opens every 46 ms.  The wave speed in the
hot exhaust gas is about 1400 ft/s, according to the CAFE report on tuned
exhaust. So, the acoustic travel time from valve to tail pipe and back to
valve is 7.7 ms (for a 65" pipe).  That means the returning pulse due to
the valve cracking open is sucking the exhaust gas out of the cylinder for
the latter part of same opening of the exhaust valve.  In my pervious post
I said that the return pulse aided the NEXT exhaust stroke.  That would
require 32 foot long exhaust pipes!

All this has me wondering if Chuck Brenner's system works by multiple
reflection.  His system has a reflection at the tail end, and one
at the 3->1 junction.  And pulses can bounce back and forth
a few times...

Or, perhaps it's ok for the return rarefaction pulse to arrive in the
middle of the valve opening.  still helps clear out the gas.

hmmmm....

it would be nice to have a controlled test of chuck's exhaust.

-Jeff Peterson




------

JBP wrote:

> Tuned exhaust is a close to a free lunch as you are likely to come across.
>
> Simplifying a bit, it works like this:  When the exhaust valve opens a
> pulse of exhaust gas enters the exhaust pipe.  It's a sound wave, a POP,
> which travels down the pipe.  When the pulse hits the tail end of the pipe
> there is a reflection of the sound.  As it turns out, the reflected POP is
> inverted. That is, the reflected pulse is a POP of LOW pressure gas.  
> This pulse travels back up the pipe to the exhaust valve and gets there
> (assuming a 65 inch pipe and 2600 rpm) while the valve is open for the
> next exhaust stroke. The returning pulse actaully sucks the exhaust gas
> out of the cylinder.
>
> good for maybe...10-20 HP.
>
> cold air induction is another cheap power booster...more oxygen
> molecules in every gulp.
>
> another 10(?)...
>
> and all with no moving parts.
>
> cheers,
>  
> Jeff Peterson
>
>