[Diy_efi] sequential injection timing

[Mark Claywell]

> > It might be that injecting onto the back of the hot intake valve helps
> > vaporization.
> 
> Yes, but the primary action to get the fuel *burnable* is the exhaust, at
> overlap that atomizes the fuel.

I would have to disagree with that, as would I think most fuel injector
engineers. There has been a large push by Deplhi and Siemens among others
to work on injectors with a bent spray (or gamma angle) to allow proper
targeting of the injector spray. Proper targeting is a large portion of
getting good mixture preparation. 


> >I think that the injection timing really only matters for
> > idle and part throttle,
> 
> Yes.

Injection timing is important for emissions, cold start, throttle response,
and making MBT (max. brake torque).

> >since under moderate to heavy load the injector
> > would be open more than closed -- to the limit that under WOT it would
> > be mostly open all the time anyway (say 70-90% duty cycle) so it
> > wouldn't really matter much.
> 
> True.

If you can decrease injection time for the same amount of mass injected
without letting SMD suffer, injection timing can become more important,
even at high load/rpm sites. 

> With really large injectors, there is at times much to be gained with a
> single batch fire system.  Firing the injectors twice as often helps with
> atomization.  My little 3.8L with 55#/hr injectors is much sweeter in
batch
> mode then SEFI.

Is this under transient or steady state conditions? SMD usually suffers at
close and open of the injector, but I have heard of improvements in
transient fueling with multiple injections per cycle on some setups. 

mark




> Bruce
> 
> > Brian
> 
> 
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> 



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