On Fri, Jun 4, 2010 at 12:48 PM, Scott Daniel - Turbovans <
scottdaniel@turbovans.com> wrote:

> hmmmm...
> EFI fuel mixture is determined by how long the injectors are held open, and
> the fuel pressure behind them.
> So I suppose, in that sense low fuel pressure will affect mixture.
> If the oxygen sensor is working and it's in closed loop, there is some
> mixture correction feedback of course.
>
> low fuel flow itself won't affect mixture per se, too much I don't think.
> You'd have low power if you had low fuel delivery rate.
>
>
> I built a 97 DOHC 2.5 Subaru engine conversion, and at first we had a clear
> cut off at 4,200 rpm ...
> and we wondered if it was the smaller fuel outlet on the tank, cause that's
> what it had, rather than the bigger one.
>
> that turned out to be lack of a good Vehicle Speed Signal,
> so there was that 165 hp, 6,200 rpm engine, running just fine off the
> smaller fuel outlet at the tank ...
>
>
   That is why some Tuners get such good results using Fuel Pressure
Regulators that can be adjusted and have rising rates, I guess.  They go on
the dyno and turn the adjuster on the Rising rate fuel pressure thingy and
get up to 40 extra HP...at least that was the case on my ~400 hp Bosch
90s-era Porsche EFI with that type a fuel pressure regulator.  They would
tune it by "The Flat"....in like 1/8 of a turn = 1 Flat...   I think the
injector spray pattern must be quite sensitive to fuel pressure as well as
to duration of opening and fine tuning the pressure was good for real
improvements in the function of the combustion event...

  We would get "close" via road testing and data logging and then go on the
dyno for final tuning and do repeated 'pulls' while adjusting the fuel
pressure regulator for the most HP and the least torque...(we wanted less
torque to keep the gears happy)
  Don Hanson

> proper mixture..
> and mixture is more related to fuel pressure, than to fuel delivery volume.
>
> Scott
> www.turbovans.com
>