[Diy_efi] Injector operation

[Tlsalt at aol.com]

peterw,

Do you know of any sites that have timing diags of injector on time vs inlet
open time ? I am trying to get my head around the various injection
strategies.

Thanks

Hello Peter,

Most of what you are looking for is in the archives.  A lot is imbedded in 
the periodic "sequential debates", which almost appear to be a syndicated 
network television program.  The tallest defended of  "batch" is no longer 
here, you will have to look back for that perspective.  It is worth it.

When you are trying to get your head around the injection strategies, it is 
good to think about the time available for each event. The inlet open time is 
a good one. The cycle time ( 2 revs.,100% duty cycle) really makes most of 
the decisions. The inlet valve is only open 35-40% of the cycle time on most 
road engines. To minimize injector size for low speed operation, injectors 
are usually sized for 85-90% of the cycle time (maximum "on" time).  So, once 
the injectors are above 35-40% duty cycle, it is not possible to fit the 
injection event into the time that the inlet valve is open.  At peak 
delivery, you are firing at a closed valve a lot of the time.  There are many 
posts in the archives explaining the benefits of sequential and suggesting 
that sequential is timed to the opening and closing of the inlet valve, but 
you are more interested in the responses to these posts.   There is a good 
one from an ex OEM EFI guy about the benefits of firing at a closed valve.  
And the benefits of firing the injector at the same time in the cycle for 
each cylinder and how any bad side effects (pooling, puddling, vaporization, 
voodoo vapor pressure, etc.....) will at least be the same for all cylinders. 
As far as timing diagrams, I haven't seen any on the web, but the only 
acronym I've seen them use describes injections timing based on the closing 
of the inlet valve.  There were some mechanical injection systems timed to 
the inlet opening, but they operated on at least 10 times the pressure.

Paul Saltwick

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