[Diy_efi] Seqential or Batch??

[life speed]

You've listed many reasons why sequential is only
incrementally better than batch.

Sure, it's not like switching from a carb to EFI.  But
the improvement from sequential is noticeable and
worthwhile.  Idle quality, part throttle response and
economy are all improved.

A performance engine can especially benefit, as the
uneven airflow caused by a lumpy cam has less impact
on mixture consistency.  A good sequential ECU can
also adjust injection angle to employ sufficient lead
on the valve event to get the full load of fuel into
the cylinder before the valve closes.

Large, low-Z injectors are appropriate.  This makes a
proper injector drive circuit a must.  Correctly
driven, even large injectors can be metered accurately
at idle.  I use 96 lbs/hr injectors with a 241 degree
@ .050 cam, and the engine idles clean and smooth at
700 RPM.

Lifespeed

--------------------------
The batch 
fired system has the advantage of being able to inject
fuel for the 
entire period of crankshaft rotation whereas the timed
system technically 
only has the time available that the air is flowing in
the intake 
runner. This is determined mainly by the camshaft
characteristics. On an 
average performance cam having 220 degrees of intake
duration measured at 
.050 valve lift, the sequential system has only 61% of
the time to 
inject the fuel as the batch fired system. As such,
true, timed, sequential 
systems must have larger injectors fitted for a given
hp. It should be 
remembered that there is little airflow and velocity
in the port and 
runner until the valve is open a fairly significant
amount. Starting the 
injection sequence early and finishing late, partially
negates the 
supposed advantages of timed injection. On a high
revving engine, there are 
only a few milliseconds available to inject before the
next cycle 
begins. 


	
		
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