Date: Tue, 18 Sep 2007 14:24:27 -0700
Reply-To: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Shazam <scottdaniel@TURBOVANS.COM>
Subject: Re: Rich on side, lean the other?
In-Reply-To: <1b0df96d0709181357ndd2e826icda3a8243cfb5c21@mail.gmail.com>
Content-Type: text/plain; charset="US-ASCII"
My you have a way. OK, 'star' as opposed to 'bus' - fine. Now what is 'PI? '
Stands for Private Investigator in the normal world as far as I know.
Acronyms and abbreviations are great if people know what they are, and
really fun if there is just enough context to be able to figure out what
they mean - now what's with ending in
"PI" ? Point Intended , pointing inward..........etc.
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
tinker man
Sent: Tuesday, September 18, 2007 1:57 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Rich on side, lean the other?
topology = wiring scheme
And borrowing from electrical wiring jargon (and also networking), In
this case it's a STAR topology, where all (hi-power in this case)
clients are connected at a central point = star, as opposed to BUS
topology, where they are connected along it's path, just like
passengers hopping on a bus along it's way (PI?...).
On 9/18/07, Scott Daniel - Shazam <scottdaniel@turbovans.com> wrote:
> "topology" ?? whazzat mean in english ?
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> tinker man
> Sent: Monday, September 17, 2007 5:30 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Rich on side, lean the other?
>
> 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
> >
>
>
|