[Diy_efi] sequential injection timing

[Mark Claywell]

> So what is the optimum "targeting"?
> 
> 1) Place the injector as close to the intake valve as possible and squirt
on

I know that GM usually trys to keep injectors within 100mm from the back of
the intake valve. This is straight from the mouth of a GM engineer. This is
also typical practice at other companies.  Moving the injector away from
the valve can result in a longer time for evaporation in the port, but can
lead to more wall wetting, and is considered bad for throttle response. F1
and other high revving engines will often have the injector at the top of
the trumpet for cooling effect and are willing to suffer a little drop in
throttle response for power increase. Although they run 400+psi at the
rail.

> it?
> 2) Place the injector a little upstream so that intake turbulence gives a
> good mixture?

Gives more time for fuel to evaporate, but again can lead to issues with
wall wetting if the fuel is not atomized finely enough.  Heat from intake
valve and the high shear flow from the intake valve upon opening give rise
to most of the mix. prep with closed valve injection scenario.

mark





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