[Diy_efi] Injector operation

[Marcell Gal]

Hi,

Paul wrote:
> 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

Very good abstract.
For the same cam (and engine), there is not much difference in
peak power between sequential EFI and other injection timing.
If you only need hi-RPM performance, and don't care about idle,
a TBI is not a very bad choice (and easy to install). I read that
many dragsters do TBI..

               BUT!

For good hi-RPM power you need aggressive cam, with large
intake - exhaust overlap.
If you want the same car to have low fuel consumption 
(and HC emissions) near idle or in city (stuck befind other traffic) 
you need well timed injection to spray after the exhaust has closed
at low RPM (to prevent fuel leaving before combustion).
Well timed injection is hard to do with TBI and impossible with batch-
port FI.
So sequential port EFI is related to power - but only indirectly,
letting you use a more aggressive cam and still reasonable fuel 
consumption at city-driving . 

    Marcell

-- 
anyway, for power stay with 2 stroke and GDI as long as you can ;-)

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