Date: Tue, 18 Sep 2007 02:30:05 +0200
Reply-To: tinker man <tinkerman007@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: tinker man <tinkerman007@GMAIL.COM>
Subject: Re: Rich on side, lean the other?
In-Reply-To: <46ed68f3.0735640a.76e7.ffffe188SMTPIN_ADDED@mx.google.com>
Content-Type: text/plain; charset=ISO-8859-1
Simple answer? Because it's connected that way at the ECU - take a
look INSIDE the ECU where the connector is soldered to the PCB and
you'll see that all four injector outputs are indeed wired in parallel
(Euro Digijet 025 906 021F, no reason others versions are different).
Technical answer?
1. For better performance: because of the high instantaneous currents
involved driving the injectors and the limited wiring gauge available,
each injector is connected right at the driving source, the ECU, to
eliminate voltage drops (=> lower drive = reduced and inconsistent
performance). Just like all POWER circuits in our home connect right
to the fuse box, not one after the other in parallel on the same line
coming from the fuse box, because each load further down the line
would see a lower voltage due to voltage drops (magnified by the
higher current of several loads in parallel) . Lower power circuits
(e.g. lights) are indeed often cascaded in parallel. If we had
unlimited gauge wire then this would not be a problem, but unlimited
gauge creates physical implementation problems.
2. Keeping the above in mind, It's easier for wiring harness
manufacture for each wire to go to a separate pin at the ECU
connector. Otherwise, there would have to be a junction somewhere and
again voltage drops would accumulate due to the limited wiring gauge
from the ECU to this junction and reduced performance.
3. Redundancy/reliability - in case there's a problem in one of the
circuits/injectors (e.g. lower resistance/partial short between
windings), preventing the culprit from robbing all the drive power
from other injectors (again lowering performance).
Anyway we look at it, even if they fire in parallel, this topology is superior.
TM
On 9/16/07, Michael Elliott <camping.elliott@gmail.com> wrote:
> On 9/16/2007 8:31 AM Raymond Paquette wrote:
>
>
> >
> > I don't doubt that you know what you're talking about, but that seems
> > bizarre. Why then is there an injector at each cylinder, instead of one big
> > one in the throttle body? Faster response? Why not more than one per
> > cylinder, or one on each bank?
>
> Bentley's 97.55 shows each injector getting its own individual feed from
> the ECU.
>
>
> --
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> KG6RCR
>
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