[Diy_efi] Donegan ECU

[Mike]

At 03:34 AM 1/8/07, you wrote:
>When you say 'geared to', do you mean mechanically
>coupled?

no :) I was being figurative, I generally like PWM approaches
and "connecting" the PWM drive to a engine speed coefficient
derived factor might result in less pump wear and reduce heating etc.
I have a fairly large new pump thats almost 5 times the rating of
my present unit but has no built-in one way valve and uses about twice as
much current, so I was musing on that with some PWM drive
as pre-emptive flow control etc and my email might have been me
thinking 'out loud' ;)

>No rules that say the pressure pump can't be close to,
>or right next to, the fuel rail. In fact, for
>retrofitting, that can make things easier. That
>eliminates the 'dead end piping' issue.

Um, having it closer might make matters so much worse, I can
visualise all sorts of sampled data system oscillations getting
second and third order effects, which would not be trivial to
handle, but then again fluid is mostly incompressible, the length
of piping in conventional setup might be assisting damping of
fuel/injector pulses. As Bernd has suggested in reply to your
post and earlier - it just seems a heck of a hard way to do it
with all sorts of added complications for something that already works !

The dead piping elimination you suggest becomes a nonsequeter
ie. Why not just leave it as return type feed, ie There is a logical
discontinuity in approach if you want to move the pump to get
around control issues but then make it (local) return anyway (?), and
in any case wouldnt that heat the fuel more as it cant 'sink' heat
through the main tank. ie. It doesnt follow Donegan's intention just shifts the
mechanics around and adds another potential problem, you'd still
need some pump to get it from the tank to the engine bay esp to
avvoid cavitation issues or even Priming ( !)   Maybe I
missed the point of your comment but I cant see at moment what
else you could have been driving at ?

The good thing about a return type with PWMing the pump and having
a proportional valve type fuel pressure regulator (controlled or trimmed
by the same controller as for the pump) is it can extend and
add some intelligence to the existing return system which already works
quite well but adds option of less wear and tear on pump and better
control of fuel vapourisation and no need for any canister to hold last
pressure and its associated valve/solenoid,

In effect adding an electronic/processing "trim" to an existing reliable and effective system...

ps: Have updated my web page, starting to gear my fuserail product to
any other earlier car renovations and street car models as well as more
Holden models where the existing fuse rail is relocated in cabin, when the nice
looking new parts turn up this week, see head of web page from link
below :)




Regards from


Mike Massen
Network Power Systems
Lab 08 9444 8961
Mb 0438 048961
Perth, Western Australia
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