Accel enrichment

[PNefdt]

In a message dated 98-03-23 23:01:12 EST, you write:

<< At 09:08 PM 3/23/98 -0500, you wrote:
 >
 >
 >>Let's review.  Steady state at 20% throttle equals 19 inches of vacuum.
 >>40% throttle equals 16 inches.  When the throttle snaps from 20% to 40%,
 >>the needle will drop to as low as 10 inches.  The pressure in the
 >>manifold goes beyond the upcoming steady state value, then sinks back to
 >>the new value.  That means there are more molecules bouncing around in
 >>the manifold than at steady state.  I can't for the life of me visualize
 >>why.
 >
 >When you open the throttle, a whole bunch of air rushes in.  As the
 >pressure equalizes, the air is still moving.  The inertia of the fast
 >moving column of air "rams" more air in.  This effect is used to increase
 >low-end torque in an engine.  An engine designed for low-end torque will
 >have narrow passages in the intanke and exhaust manifolds.  This
 >increases the velocity of the gas.
 >
 
 I agree that has some effect, but the increase in pressure over the new
 steady state value lasts for as long as the vehicle accelerates.  The
 rushing in effect is almost immediate.  The only thing that comes to mind
 is possibly the accelerating piston speed in some way causes an increase in
 the flow rate.
 
 >
 >The fuel comes out of solution because the pressure has gone above the
 >vapor pressure of the fuel.
 >
 
 Oh yea, that partial pressure thing.  I remember that.
 
 >Ray Drouillard, BSEE
 >(who was forced to take physics and thermodynamics in school, and is
 >currently working at earning a conical hat)
 
 
 Joe Boucher
 '70 RS/SS Camaro  '81 TBI Suburban
  >>

It's actually simpler than all this;
25% open on any butterfly valve. is 75% flow.
It's a sine function.
Regards,
Peter