> > -----Original Message-----
> > From: jon@dakota-truck.net
> >
> > In the August 2008 issue of Mopar Muscle
> there's an article on a
> > '69 Satellite into which the owner transplanted a
> 318 Magnum from an
> > '02 Dak. (http://tinyurl.com/5amxf6) In the
> article, the owner of
> > the vehicle says that the Magnum engines have a
> "fundamental flaw"
> > with the fuel system. He says:
> >
> > "Chrysler feeds the driver-side bank of injectors
> from the fuel pump
> > in the tank, and then they use a very skinny hose
> to go between the
> > fuel rail on the driver's side to the one on the
> passenger side. So
> > when you fire up the engine, cylinder numbers five
> and seven fire.
> > When they fire, the whole pressure in the rail
> drops momentarily, and
> > then they want to fire cylinder number two, which
> is as far away as
> > you can get from that spot. So the fuel pressure
> drops over there,
> > and that cylinder always ends up lean."
> >
> > He says used a prototype set of fuel rails from
> Ross Machine
> > Engineering to cure the "number two cylinder
> starvation problem".
> >
> >
> > Something about the above didn't sound right to
> me, so I thought
> > I'd run it by you folks and see what you thought.
> (Plus, there
> > were a few goofy things about the car that kind've
> made me question
> > the guy in general; for example, his intention
> with the EFI system was
> > to set up the car for the best fuel economy as
> opposed to power, and
> > yet when he installed an aftermarket 5-speed, he
> chose one with a 1:1
> > top gear instead of an overdrive...)
> >
> >
> > I'm certainly no fluid engineer and don't even
> play one on TV, but
> > his explanation doesn't make sense to me. The
> distance between the
> > fuel feed and a particular injector shouldn't
> matter because the
> > entire rail is pressurized and it is the pump
> which is creating the
> > pressure. Its not like the injectors are sucking
> fuel out of the rail
> > and then the pump has to kick on and make it back
> up or something.
> > The injector is just a gate; the only reason fuel
> comes out when it is
> > opened is that the pump is pushing fuel up into
> the rail from the
> > tank, so as long as the crossover tube outflows
> any individual
> > injector, the pressure in the fuel rail should
> remain the same at all
> > times. Also, his claim about having #5 and #7
> firing together
> > dropping the fuel pressure a bit doesn't seem
> right either. Its not
> > like they are firing at the same time, the firings
> are spaced out
> > equally across all 360 degrees of engine
> revolution. So, if firing
> > two injectors sequentially was enough to drop the
> fuel pressure in the
> > rail slightly, then the next firing would drop it
> a little more, and
> > so on until soon you'd have no pressure at all.
> It is my contention
> > that if even a single firing is big enough to drop
> the pressure in the
> > fuel rail such that it is not back up to its
> pre-fire pressure by the
> > time the next injector opens, then your fuel pump
> is not big enough or
> > you've got some other restriction prior to the
> fuel rail.
> >
> >
> > Anyway, does the above make any sense, or am I
> just off my game
> > today? :-) For those of you who have torn into a
> bunch of these
> > engines (Bernd?), has it been your experience for
> the #2 cylinder on
> > Magnum engines to be running lean?
> >
> > -Jon-
>
Forgive my ignorance here, but I seem to recall that
on FI systems, you need a return to tank line.
Something about once the system is pressurized, excess
fuel is routed back to the tank so the rails aren't
over pressurized. Plus the fact the fuel pressure
regulator on some vehicles is integral to the in-tank
fuel pump. Again, not knowing for sure, I have no idea
if that component reads fuel pressure on the output
side of the pump, but it would seem to me that it
would read the pressure on the return line. Simply
because you'd want the system to read the pressure on
the entire system not just what the pump is putting
out, thus maintain even pressure at the fuel rails.
Personally, I think the guy has been smokin' sumpin'
or he's inhaled too much of his own exhaust fumes.
Ray Irons
83 Yamaha Seca 750.......
97 Jeep Grand Cherokee...
97 Suzuki Bandit 1200S...
05 Dodge Grand Caravan...
.........................
Dakota-less
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