DFI, Batch Fire, and other myths

[xxalexx at ix.netcom.com]

> The sometimes less than accurate GM classes I've attended teach that
> injection should occur when the intake valve is closed,and be
> completed immediately prior to intake valve opening.  This would make
> use of the heat in the head of the valve help keep fuel from pooling.
> This was mentioned earlier.  This might be GM's approach to sefi. 
> According to a service bulletin, the 3.8l engine suffers from carbon
> accumulation on the back of the intake valve which significantly
> reduces performance.  I've seen the effects. It's very similar to
> losing the accelerator pump on a carb'ed engine, and the exhaust is
> excessively rich.  My thought was the carbon is insulating the valve,
> preventing vaporization.
> Shannen
> 
I always thought carbon caused hot spots, this would help 
vaporization.  You would be loosing the orginal design shape
of valve causing different cylinder entry conditions and also
reduction in flow, thou velocity would increase helping atomization.
alex