I've been researching SIDI combustion systems, and I can't find the accurate definitions of mixture motion and charge motion. I've googled those terms but found lots of contradicting information. Can anyone define and explain the differences between the two principles?

 

I'll take an educated guess here and say that charge motion refers to the
port speed or velocity of the air motion where as the mixture motion explains
the swirl and tumble (turbulance) properties of the airflow.
One of the major design parameters of the GEN III (Sperry brothers) was to
create the cylinder heads and intake manifold as one system. To work togeth
er creating a hurricane motion that would increase in port velocity as it app-
roached the valve in order to effectively atomize and suspend the fuel drop-
lets. Even though the injector is better than any carburetor and was ideally
located...they felt that less emissions and more power could be had if the
intake tract had a perfect balance of swirl and tumble but not too much of
either. GM began testing these principles with the iron LT1 heads(pre vortec)
What they learned in the early nineties carried over into the LS program. It's
believed that the surface area of thousands of tiny fuel particles will burn
way more efficiently and cleaner (lower Brake Specific Fuel Consumption).....
this refers to the number of pounds of fuel per hour needed to support each
horsepower the engine makes.
Now with the direct injected LT1 engines having a perfect injector location,
the port can now be big and only needs to flow air. Then the torque manage-
ment modulation of the throttle body is used to create a restriction which
enhances air velocity at low engine speeds.

 

Awesome. Thanks for the detailed information.