[Diy_efi] Donegan ECU

[Bernd Felsche]

On Monday 08 January 2007 04:34, Carter Shore wrote:
> On 207-01-08 Mike <niche at iinet.net.au> wrote:

> > mmmm, Think I'd prefer (from a control systems perspective) a
> > fuel pump controller geared to engine speed (say 8 speeds) with
> > a PWM fuel pressure regulator (proportional valve type) close to
> > the fuel rail in a classical return system - my educated gut
> > feeling is that this would be rather more stable than a PWM
> > driven fuel pump and dead end piping...

> When you say 'geared to', do you mean mechanically
> coupled?

Probably not...

> No rules that say the pressure pump can't be close to,

Try the rule of not operating the pump in an environment hotter than
allowed by its specifications. :-)

It is possible to build pumps that'll tolerate under-bonnet
temperatures but off-the-shelf ones, designed for under-tank or
under-body mounting, typically don't.

> or right next to, the fuel rail. In fact, for

Or "in" the fuel rail.

> retrofitting, that can make things easier. That
> eliminates the 'dead end piping' issue.

Diesel engines have worked like that for ages... especially the ones
with unit injector pumps.

Heat is more of a problem with gasoline than diesel; especially
heat-soak. However, the feed pump from the fuel tank can be set up
to flush the high-pressure pump and rail before starting. There are
half a dozen ways that I can immediately think of doing that.

There are a few niggly problems about there being enough of a fluid
pressure damper in the system so that pulsations of fuel pressure
from the pump and the injectors don't wreak havoc with the fuel
pressure control system and to ensure a consistent (intended) fuel
pressure at the injectors. There is sometimes a pressure
accummulator between the high pressure pump and the injectors, and
in some systems a separate damper to handly dynamic fluctuations
(typically when the fuel rail volume isn't "huge" wrt injected
quantity).

-- 
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