Date: Wed, 27 Jul 2011 15:37:52 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: dumb fuel injection question
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One way to express it is ..
it's not timed sequential injection.
Digijet and Digifant injection are not that sophisticated.
the ecu fires all four injectors like on big 4-part injector.
'The only' variable is how long, in milliseconds the ecu holds the injectors
open.
( minor variation is fuel pressure, which changes slightly relative to
intake manifold vacuum ...as affect by the fuel pressure regulator )
so ...the injectors are firing 'whenever' ..
and not during say, a give cylinders intake stroke, as you would expect.
it's kind of a sloppy way of doing it ..but good enough for the technology
of the era, and the emissions requirement then.
for comparison ..
1990 Subaru and later..
there's a camshaft position sensor, and crank shaft position sensor ..
so the Subaru ecu knows where the engine is at each instant, what phase
things are in ..and fire each injector at the optimum time ....called
'sequential EFI'. Also interesting ..
the injector ..has a twin spray pattern ..each side directed right at it's
intake valve. There being two intake valves ( and 2 exh. ) valves per
cylinder.
The waterboxer ecu only knows..
that the engine is turning, what the rpm is, what the coolant temp is, what
the air flow meter is telling it about air flow, and throttle position 'a
little' ... ...the ecu only knows if it's at idle. or wide open, or
somewhere in between ( Subaru is far more sophisticated and variable across
the range of throttle plate position ) ..
So ...
the waterboxer ecu just fires the injectors away .
as one big 4 part injector ..any injector plug can go to any injector ..
and it's based only on how long the injectors are held open, nothing to do
with which cylinder, or what phase/stroke that cylinder is on etc.
rather crude actually.
and part of why waterboxer engines produce less power, burn more fuel, and
have higher emissions than much more modern engines. I included how Subaru
does it so broaden the reader's appreciation and insights on how this all
works. Hope you can dig that.
Scott
www.turbovans.com
----- Original Message -----
From: "David White" <sirgrumpsalot@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, July 27, 2011 1:28 PM
Subject: dumb fuel injection question
>I can rearrange the fuel injector wires on each side of the engine
> without effecting how it runs, suggesting that they must inject fuel
> into every cylinder at the same time. Isn't this a waste of fuel? What
> am I missing?
